Dissertation submitted in partial fulfillment of the Btech. course.
ROBOTIC ARM Under the Guidence of Submitted By Abhishek Kaushik SG-119836.
Robotic Arm Introduction:In this project we will control the robotic arm. In robotic arm we will use stepper motors for controlling purpose. Robotic arm is one of the major projects in today automation industries. Robotic arm is part of the mechatronic industry today’s fast growing industry. In this project we will three stepper motors for controlling purpose. But we will try to control three functions with three motors. First of all we tried to make it using 8051. But we don’t have knowledge of 8051 programming. So we used combination of switch to control the arm. First of all we make 12v supply
To make 12v supply we used step-down transformer. Stepdown transformer gives AC 12v to rectifier circuit. We used IN 4007 diode for rectification purpose. After rectification we will get 12v DC. But this supply is not purely DC. To make it DC we used filter to remove ripples. For filtering we used 1000µf capacitor.
First of all we will design the jaws of robotic arm. It will be of following shape
2”
3 3”
3” Jaws will be metallic. They will be made of sheet metal. ARM: arm will be made up of wood material.
2 1 3 inch
10 inch
Stepper motor stepper motor have five wires . One for common supplies another four for winding purpose. By giving different signal to each we will control the stepper motor.
The wires from the Logic PCB connector to the stepper motor in a TM100 Disk Drive are as follows
This kind of motor has four coils which, when energised in the correct sequence, cause the permanent magnet attached to the shaft to rotate. There are two basic step sequences. After step 4, the sequence is repeated from step 1 again. Reversing the order of the steps in a sequence will reverse the direction of rotation. a. Single-Coil Excitation - Each successive coil is energised in turn. Step
Coil 4
Coil 3
Coil 2
Coil 1
a.1
on
off
off
off
a.2
off
on
off
off
a.3
off
off
on
off
a.4
off
off
off
on
This sequence produces the smoothest movement and consumes least power. Single-Coil Excitation
Inside a Stepper Motor The stepper motors we are concerned with are those taken out of old 5 ¼" floppy disk drives. Some of the comments below may therefore not apply in all cases…
A
B
C
D
The simplest way to think of a stepper motor is a bar magnet and four coils. When current flows though coil "A" the magnet is attracted and moves one step to the right. Coil A is then turned off and coil "B" turned on. The magnet moves another step to the right. Coil "B" is then turned off and coil "C" turned on. The magnet moves another step to the right and so on… A similar process occurs inside the stepper motor, but the 'magnet' is cylidrical and rotates inside the coils. In order to make a stepper motor rotate you must turn on each coil in the correct sequence. The motor will continue to rotate as long as you continue the sequence. A typical code sequence would be: count := 1 repeat port[888] := 1;
delay(50); port[888] := 2; delay(50); port[888] := 4; delay(50); port[888] := 8; delay(50); count := count + 1; until count > 50; NOTE1: The "delay" is needed provide enough time for the magnetic field inside the coils to build up and the magnet to move. Without the 'delay', the coils will switch on and off so fast that the magnet will not get a chance to be attracted and it will not move. NOTE2: To reverse the direction, simply reverse the output order.
The Coil Switch-on Sequence The stepper motor in a 5 ¼" floppy drive (the one that moves the head back and forth over the disk - NOT the one that spins the disk) has FIVE wires coming out of it. If you are lucky they will be coloured Brown, Yellow, Red, Blue and White. (Many of the ones I've looked at have five brown wires!) The 'four' coils described above are actually arranged as two 150 ohm coils with centre taps. The centre taps are lines "1" and "2" in Figure 1.1. This line is generally called the "common". Figure 1.1
Measuring the resistance between each of the wires coming out of the motor produces the following readings: Measured Resistance (ohms)
1
2
1a
1b
2a
2b
1
-
0
75
75
75
75
2
0
-
75
75
75
75
1a
75
75
-
150
150
150
1b
75
75
150
-
150
150
2a
75
75
150
150
-
150
2b
75
75
150
150
150
-
One of the five wires is the 'common'. You can easily identify the common with a multimeter. It will be the one that reads 75 ohms between it and all the other four lines in turn. The other four are impossible to identify using a multimeter. You will need to use an interface and connect it to a computer for the next step. (You could just use wires from a 12 volt battery if you wanted.) Using the Demonstration Interface to Drive a Stepper Motor (For details about the Demonstration Interface see: robokit.html)
•
Connect a 12 volt DC supply to the demonstration interface (in place of the 9 volt battery).
•
Solder the 'common' lead to the positive line on the Demonstration Interface.
•
Solder each of the other four wires to the points where the resistor connects to a line from the ULN2803. (Keep the wires in order from the common wire and solder them to data lines 0, 1, 2, and 3.)
•
Connect the interface to a computer and send 'out' commands of 1,2,4 and 8. The motor should 'step' in a clockwise, or anti-clockwise direction. - If it 'jerks' as it tries to change direction, or simply 'shudders' you will need to experiment with other control sequences.
Hopefully your motor moved in a consistent direction. Now you need to write code as outlined above and try for complete rotations
Working : Sensor:-In this project we will connect three pin Sensor have three pins one VCC, ground and out. It works on 38Khz. Signal decoded by 89s52 at pin no p3.3. output of microntroller will be connected at port1.ports 1st and 2nd pin is connected to isolator circuit. Isolators are optocoupler pc 817. pc 817 is 4 pin ic. In PC 817 contain LED and phototransistors in built. When led work then transistor work. Negative of in built LED in pc 817 is connected to microcontroller. Positive of microcntroller is connected to VCC 5v. 3 pin of PC 817 is connected to ground. Output of PC 817 is pin 4 . 4.7k ohm is connected to VCC. Output of pin 4 is connect to bases of transistors npn and pnp. H bridge circuit contain transistors. Hbridage circuit work as current and voltage amplifier. Bases of transistors connected to output of pc817. and emitters are output to motors. We are using DC geared motors.. DC geared motors are of 100 RPM and 12 v. It take 50 to 100 mA current.
POWER SUPPLY FOR DIGITAL CIRCUITS
Summary of circuit features •
Brief description of operation: Gives out well regulated +9V output, output current capability of 100 mA.
•
Circuit protection: Built-in overheating protection shuts down output when regulator IC gets too hot.
•
Circuit complexity: Simple and easy to build.
•
Circuit performance: Stable +9V output voltage, reliable operation.
•
Availability of components: Easy to get, uses only common basic components.
•
Design testing: Based on datasheet example circuit, I have used this circuit successfully as part of other electronics projects.
•
Applications: Part of electronics devices, small laboratory power supply.
•
Power supply voltage: Unregulated DC 8-18V power supply.
•
Power supply current: Needed output current 1A.
•
Components cost: Few rupees for the electronic components plus the cost of input transformer.
DESCRIPTION OF POWER SUPPLY This circuit is a small +12 volts power supply, which is useful when experimenting with digital electronics. Small inexpensive wall transformers with variable output voltage are available from any electronics shop. Those transformers are easily available, but usually their voltage regulation is very poor, which makes them not very usable for digital circuit experimenter unless a better regulation can be achieved in some way. The following circuit is the answer to the problem. This circuit can give +12V output at about 1A current. The circuit has overload and terminal protection.
IN 4007
1
7812
3
+12V
2 4700 uf
Circuit diagram of power supply
1000 uf
The above circuit utilizes the voltage regulator IC 7812 for the constant power supply. The capacitors must have enough high voltage rating to safely handle the input voltage feed to circuit. The circuit is very easy to build for example into a piece of Vero board.
1
2
3
Pin diagram of 7812 regulator IC
PIN 1 : Unregulated voltage input PIN 2 : Ground PIN 3 : Regulated voltage output
DC motors These are the motors that are commonly found in the toys and the tape recorders. These motors change the direction of rotation by changing the polarity. Most chips can't pass enough current or voltage to spin a motor. Also, motors tend to be electrically noisy (spikes) and can slam power back into the control lines when the motor direction or speed is changed.
Specialized circuits (motor drivers) have been developed to supply motors with power and to isolate the other ICs from electrical problems. These circuits can be designed such that they can be completely separate boards, reusable
from
project
to
project.
A very popular circuit for driving DC motors (ordinary or gearhead) is called an H-bridge. It's called that because it looks like the capital letter 'H' on classic schematics. The great ability of an H-bridge circuit is that the motor can be driven forward or backward at any speed, optionally using a completely independent power source.
The H-Bridge Circuit
This circuit known as the H-bridge (named for its topological similarity to the letter "H") is commonly used to drive motors. In this circuit two of four transistors are selectively enabled to control current flow through a motor.
opposite pair of transistors (Transistor One and Transistor Three) is enabled, allowing current to flow through the motor. The other pair is disabled, and can be thought of as out of the circuit. By determining which pair of transistors is enabled, current can be made to flow in either of the two directions through the motor. Because permanentmagnet motors reverse their direction of turn when the current flow is reversed, this circuit allows bidirectional control of the motor.
The H-Bridge with Enable Circuitry
It should be clear that one would never want to enable Transistors One and Two or Transistors Three and Four simultaneously. This would cause current to flow from Power + to Power - through the transistors, and not the motors, at the maximum current-handling capacity of either the power supply or the transistors. This usually results in failure of the H-Bridge. To prevent the possibility of this failure, enable circuitry as depicted in Figure is typically used. In this circuit, the internal inverters ensure that the vertical pairs of transistors are never enabled simultaneously. The Enable input determines
whether or not the whole circuit is operational. If this input is false, then none of the transistors are enabled, and the motor is free to coast to a stop. By turning on the Enable input and controlling the two Direction inputs, the motor can be made to turn in either direction. Note that if both direction inputs are the same state (either true or false) and the circuit is enabled, both terminals will be brought to the same voltage (Power + or Power - , respectively). This operation will actively brake the motor, due to a property of motors known as back emf, in which a motor that is turning generates a voltage counter to its rotation. When both terminals of the motor are brought to the same electrical potential, the back emf causes resistance to the motor's rotation.
Stepper motors Stepper motors are special kind of heavy duty motors having 2 or 4 coils. The motors will be stepping each time when it get the pulse. As there are many coils in the motors we need to energize the coils in a specific sequence for the rotation of the motor. These motors are mostly used in heavy machines. The figure shown below consists of a 4 coil stepper motor and the arrow mark will rotate when the coils are energized in the sequence.
Unlike DC motors stepper motors can be turned accurately for the given degrees.
Servo motors Servo motors unlike the stepper motor it has to be controlled by the timing signal. This motor has only one coil. It is mostly used in robots for its lightweight and low power consumption. The servo motors can also be accurately rotated by the making the control signal of the servo motor high for a specific time period. Actually the servo motor will be having 3 wires where 2 are for power supply and another one is for the control signal. Driving the servomotors is so simple that you need to make the control
signal high for the specific amount of time. The width of the pulse determines the output position of the shaft
Drives to the Nation SPECIFICATIONS : 1. Input 2. Output 3. Operation . Recommended Operation Speed Optional Motor 6. Torque rating Optional Motor 7. Voltage rating 5.
1. 2. 3. 4. 5. 6. 7.
: 230V, 1-Ø, 50HZ : 4 Step / 8 Step : Constant Current : 0 - 50rpm : 3 kg. cm. : 6 Volts or 12 Volts
FUNCTIONS AVAILABLE Reverse - forward Inching Precise Setting of Position without cumulative error. Home position defining Single or multiple axis operations in precise synchronization. Compatible with any PLC or PC for programmability. Optional programmable user interface available.
1. 2. 3. 4. 5.
TYPICAL APPLICATIONS Material Feeding Cutting & Sealing Two axis machining in machine-tool applications. Three axis PCB drilling machine. Precise valve opening & closing.
6. Precise length measurement. Stepper motor stepper motor have five wires . One for common supplies another four for winding purpose. By giving different signal to each we will control the stepper motor.
The wires from the Logic PCB connector to the stepper motor in a TM100 Disk Drive are as follows
This kind of motor has four coils which, when energised in the correct sequence, cause the permanent magnet attached to the shaft to rotate. There are two basic step sequences. After step 4, the sequence is repeated from step 1 again. Reversing the order of the steps in a sequence will reverse the direction of rotation.
a. Single-Coil Excitation - Each successive coil is energised in turn. Step
Coil 4
Coil 3
Coil 2
Coil 1
a.1
on
off
off
off
a.2
off
on
off
off
a.3
off
off
on
off
a.4
off
off
off
on
This sequence produces the smoothest movement and consumes least power.
Single-Coil Excitation
Inside a Stepper Motor The stepper motors we are concerned with are those taken out of old 5 ¼" floppy disk drives. Some of the comments below may therefore not apply in all cases…
A
B
C
D
The simplest way to think of a stepper motor is a bar magnet and four coils. When current flows though coil "A" the magnet is attracted and moves one step to the right. Coil A is then turned off and coil "B" turned on. The magnet moves another step to the right. Coil "B" is then turned off and coil "C" turned on. The magnet moves another step to the right and so on… A similar process occurs inside the stepper motor, but the 'magnet' is cylidrical and rotates inside the coils. In order to make a stepper motor rotate you must turn on each coil in the correct sequence. The motor will continue to rotate as long as you continue the sequence. A typical code sequence would be: count := 1 repeat port[888] := 1; delay(50); port[888] := 2; delay(50); port[888] := 4; delay(50); port[888] := 8; delay(50); count := count + 1; until count > 50; NOTE1: The "delay" is needed provide enough time for the magnetic field inside the coils to build up and the magnet to move. Without the 'delay', the
coils will switch on and off so fast that the magnet will not get a chance to be attracted and it will not move. NOTE2: To reverse the direction, simply reverse the output order.
The Coil Switch-on Sequence The stepper motor in a 5 ¼" floppy drive (the one that moves the head back and forth over the disk - NOT the one that spins the disk) has FIVE wires coming out of it. If you are lucky they will be coloured Brown, Yellow, Red, Blue and White. (Many of the ones I've looked at have five brown wires!) The 'four' coils described above are actually arranged as two 150 ohm coils with centre taps. The centre taps are lines "1" and "2" in Figure 1.1. This line is generally called the "common". Figure 1.1
Measuring the resistance between each of the wires coming out of the motor produces the following readings: Measured Resistance (ohms)
1
2
1a
1b
2a
2b
1
-
0
75
75
75
75
2
0
-
75
75
75
75
1a
75
75
-
150
150
150
1b
75
75
150
-
150
150
2a
75
75
150
150
-
150
2b
75
75
150
150
150
-
One of the five wires is the 'common'. You can easily identify the common with a multimeter. It will be the one that reads 75 ohms between it and all the other four lines in turn. The other four are impossible to identify using a multimeter. You will need to use an interface and connect it to a computer for the next step. (You could just use wires from a 12 volt battery if you wanted.) Using the Demonstration Interface to Drive a Stepper Motor (For details about the Demonstration Interface see: robokit.html) •
Connect a 12 volt DC supply to the demonstration interface (in place of the 9 volt battery).
•
Solder the 'common' lead to the positive line on the Demonstration Interface.
•
Solder each of the other four wires to the points where the resistor connects to a line from the ULN2003. (Keep the wires in order from the common wire and solder them to data lines 0, 1, 2, and 3.)
•
Connect the interface to a computer and send 'out' commands of 1,2,4 and 8. The motor should 'step' in a clockwise, or anti-clockwise direction. - If it 'jerks' as it tries to change direction, or simply 'shudders' you will need to experiment with other control sequences.
Hopefully your motor moved in a consistent direction. Now you need to write code as outlined above and try for complete rotations
Types of Machine Tools: Lathes: In a turning or facing operation on a lathe, the workpiece rotates to provide the cutting motion, and the feed is by motion of the cutting tool. Lathes are used for the production of all kinds of components which are symmetrical about their axis of rotation. Turning Center
( This and other pictures are from "Manufacturing Engineering" April - September 1996 magazines) Drilling Machines: The cutting action results from the rotary movement of the cutting tool or workpiece, with a feed motion of the workpiece or tool, in the direction of the rotating axis. Drilling machines are used for drilling, boring, counter-sinking, reaming and tapping operations. Vertical Drilling Center Milling Machines: Similar to drilling. In the case of milling, both the tool and the workpiece can move horizontal or vertical direction. Milling machines are used to produce flat surfaces, sink, and slot. Milling Machine Turning Centers Machining Centers (Horizontal / Vertical) Transfer Machines: A number of work stations (turning, drilling, milling, etc.) aranged behind each other, linked by the means of an automatic work transportation unit, which governs their positions and the timing cycle.
Transfer Machine Grinding Machines: Basicaly, the cutting tool provides the cutting movement on grinding machines. The contact between the workpiece and the grinding wheel is either on the wheel periphery or on the wheel face. Grinding Machine Honing Machines: The fundamental difference between honing and grinding techniques, is that when honing, the aim is only for an improvement in surface finish and dimensional accuracy. Horizontal Machining Center
Basic Types of Drilling Machines Drilling machines or drill presses are one of the most common machines found in the machine shop. A drill press is a machine thatturns and advances a rotary tool into a workpiece. The drill press is used primarily for drilling holes, but when used with the proper tooling, it can be used for a number of machining operations. The most common machining operations performed on a drill press are drilling, reaming, tapping, counterboring, countersinking, and spotfacing. There are many different types or configurations of drilling machines, but most drilling machines will fall into four broad categories: upright sensitive, upright, radial, and special purpose. UPRIGHT SENSITIVE DRILL PRESS
The upright sensitive drill press (Figure 1) is a light-duty type of drilling machine that normally incorporates a belt drive spindle head. This machine is generally used for moderate-to-light duty work. The upright sensitive drill press gets its name due to the fact that the machine can only be hand fed. Hand feeding the tool into the workpiece allows the operator to "feel" the cutting action of the tool. The sensitive drill press is manufactured in a floor style or a bench style.
Figure 1 Upright sensitive drill press UPRIGHT DRILL PRESS The upright drill press (Figure 2) is a heavy duty type of drilling machine normally incorporating a geared drive spindle head. This type of drilling machine is used on large hole-producing operations that typically involve larger or heavier parts. The upright drill press allows the operator to hand feed or power feed the tool into the workpiece. The power feed mechanism automatically advances the tool into the workpiece. Some types of upright drill presses are also manufactured with automatic table-raising mechanisms. Figure 2 Upright drill press
RADIAL ARM DRILL PRESS The radial arm drill press (Figure 3) is the hole producing work horse of the machine shop. The press is commonly refered to as a radial drill press. The radial arm drill press allows the operator to position the spindle directly over the workpiece rather than move the workpiece to the tool. The design of the radial drill press gives it a great deal of versatility, especially on parts too large to position easily. Radial drills offer power feed on the spindle, as well as an automatic mechanism to raise or lower the radial arm. The wheel head, which is located on the radial arm, can also be traversed along the arm, giving the machine added ease of use as well as versatility. Radial arm drill presses can be equipped with a trunion table or tilting table. This gives the operator the ability to drill intersecting or angular holes in one setup.
Figure 3 Radial arm drill press
SPECIAL PURPOSE DRILL MACHINES There are a number of types of special purpose drilling machines. The purposes of these types of drilling machines vary. Special purpose drilling machines include machines capable of drilling 20 holes at once or drilling holes as small as 0.01 of an inch. Gang Drilling Machines
The gang style drilling machine (Figure 4) or gang drill press has several work heads positioned over a single table. This type of drill press is used when successive operations are to be done. For instance, the first head may be used to spot drill. The second head may be used to tap drill. The third head may be used, along with a tapping head, to tap the hole. The fourth head may be used to chamfer.
Figure 4 Gang drill press Multiple Spindle Drilling Machine
The multiple spindle drilling machine is commonly refered to as a multispindle drill press. This special purpose drill press has many spindles connected to one main work head (Figure 5). All of the spindles are fed into the workpiece at the same time. This type of drilling machine is especially useful when you have a large number of parts with many holes located close together.
Figure 5 Multispindle drill press
Micro-Drill Press
The micro drill press is an extremely accurate, high spindle speed drill press. The micro drill press is typically very small (Figure 6) and is only capable of handling very small parts. Many micro drill presses are manufactured as bench top models. They are equipped with chucks capable of holding very small drilling tools.
Figure 6 Micro drill press Turret Type Drilling Machine
Turret drilling machines are equipped with several drilling heads mounted on a turret (Figure 6). Each turret head can be equipped with a different type of cutting tool. The turret allows the needed tool to be quickly indexed into position. Modern turret type drilling machines are computer-controlled so that the table can be quickly and accurately positioned.
Figure 6 CNC turret type drilling machine Drilling Process The drilling machine (drill press) is a single purpose machine for the production of holes. Drilling is generally the best method of producing holes. The drill is a cylinderical bar with helical flutes and radial cutting edges at one end. The drilling operation simply consist of rotating the drill and feeding it into the workpiece being drilled. The process is simple and reasonably accurate and the drill is easily controlled both in cutting speed and feed rate. The drill is probably one of the original machining processes and is the most widely used.
Drilling machine -important features/dimensions Pillar Drill The pillar drill has the same features as the bench drill. This drill is however free standing and is of a far heavier construction able to take larger drills. The larger drills normally have taper shanks which are located within a taper bore in the spindle end. These tapers are standardised as morse tapers.
Radial Arm Drill
The radial drill is a free standing and the workpiece is clamped in position on the base. The drill head is positioned using motorised drives.
Notes on Selection of Drilling Machines Normal pillar drilling machines (Drill Press) are specified basically by the size of hole the machine can drill in Mild Steel i.e a 16mm machine can drill holes upto and including 16mm dia in mild steel. The speed range of a drilling machine is related to the size e.g. machines for small holes down to 1mm can have speed ranges up to 8000rpm. Larger drilling machines more suited for drilling holes. up to 25mm will have a more limited range. A machine which is used to drill larger holes ( >15mm) is not generally suitable for drilling small diameter holes (< 1 mm). Smaller machines are provided with permanent chucks whilst larger machines gnerally include morse tapers for fixing the drills. Most pillar drills are manually fed using a rotating lever driving the vertical motion of the spindle. Larger machines can have power drives feeds. A belt driven spindle is often a convenient low cost option but there is a tendency in modern times to use geared /inverter drives. When drilling holes in a material a number of factors should be considered including
• • • • •
Material being drilled Hole size Hole quality. Speed /Feed required Depth of hole
• • • • •
Through or Blind Hole Need for coolant Capacity of drilling machine Method of work holding. Hand held, vice, clamped Orientation of drill (horizontal , vertical drilling, angle
• Swarf control Drilling Machines/ Machining Centres
Types of Drills Bits
For the planned skyscraper nicknamed Drill bit, see Chicago Spire.
Some drill bits: Spade, lip and spur (brad point), masonry bit, twist drill Drill bits are cutting tools used to create cylindrical holes. Bits are held in a tool called a drill, which rotates them and provides axial force to create the hole. Specialized bits are also available for non-cylindrical-shaped holes. This article describes the types of drill bits in terms of the design of the cutter. The other end of the drill bit, the shank, is described in the drill bit shank article. Drill bits come in standard sizes, described in the drill bit sizes article. A comprehensive drill and tap size chart lists metric and imperial sized drills alongside the required screw tap sizes. The term drill can refer to a drilling machine, or can refer to a drill bit for use in a drilling machine. In this article, for clarity, drill bit or bit is used throughout to refer to a bit for use in a drilling machine, and drill refers always to a drilling machine.
Contents [hide] •
•
1 Metal drills o 1.1 Twist drill o 1.2 Gun drill o 1.3 Center drill and spotting drill 1.3.1 Use in making holes for lathe centers 1.3.2 Use in spotting hole centers o 1.4 Core drill o 1.5 Left-hand bit 1.5.1 Screw extractor o 1.6 Countersink bit o 1.7 Indexable drill o 1.8 Spade drill o 1.9 Trepan o 1.10 Ejector drill 2 Wood drills o 2.1 Lip and spur drill o 2.2 Spade bit o 2.3 Forstner bit o 2.4 Step bit o 2.5 Center bit o 2.6 Auger bit o 2.7 Gimlet bit o 2.8 Hinge sinker bit o 2.9 Adjustable wood bit
• •
3 Other materials o 3.1 Diamond core bit o 3.2 Masonry drill o 3.3 Holesaw o 3.4 PCB through-hole drill o 3.5 Installer bit 4 Well drilling bits 5 Materials for bit construction o 5.1 Steels o 5.2 Exotic materials o 5.3 Coatings 6 See also 7 References
•
8 External links
•
• •
Metal drills Twist drill The twist drill bit is the type produced in largest quantity today. It drills holes in metal, plastic, and wood. The twist drill bit was invented by Steven A. Morse[1] of East Bridgewater, Massachusetts in 1861. He received U.S. Patent 38,119 for his invention on April 7, 1863. The original method of manufacture was to cut two grooves in opposite sides of a round bar, then to twist the bar to produce the helical flutes. This gave the tool its name. Nowadays, the drill bit is usually made by rotating the bar while moving it past a grinding wheel to cut the flutes in the same manner as cutting helical gears. Tools recognizable as twist drill bits are currently produced in diameters covering a range from 0.05 mm (0.002") to 100 mm (4"). Lengths up to about 1000 mm (39") are available for use in powered hand tools. The geometry and sharpening of the cutting edges is crucial to the performance of the bit. Users often throw away small bits that become blunt, and replace them with new bits, because they are inexpensive and sharpening them well is difficult. For larger bits, special grinding jigs are available. A special tool grinder is available for sharpening or reshaping cutting surfaces on twist drills to optimize the drill for a particular material. Manufacturers can produce special versions of the twist drill bit, varying the geometry and the materials used, to suit particular machinery and particular materials to be cut.
Twist drill bits are available in the widest choice of tooling materials. However, even for industrial users, most holes are still drilled with a conventional bit of high speed steel. The most common twist drill (the one sold in general hardware stores) has a point angle of 118 degrees. This is a suitable angle for a wide array of tasks, and will not cause the uninitiated operator undue stress by wandering or digging in. A more aggressive (sharper) angle, such as 90 degrees, is suited for very soft plastics and other materials. The bit will generally be self-starting and cut very quickly. A shallower angle, such as 150 degrees, is suited for drilling steels and other tougher materials. This style bit requires a starter hole, but will not bind or suffer premature wear when a proper feed rate is used. Drills with no point angle are used in situations where a blind, flat-bottomed hole is required. These drills are very sensitive to changes in lip angle, and even a slight change can result in an inappropriately fast cutting drill bit that will suffer premature wear. Drill bit geometry has several aspects: •
•
The spiral, or rate of twist in the drill, controls the rate of chip removal in a drill. A fast spiral drill is used in high feed rate applications under low spindle speeds, where removal of a large volume of swarf is required. Low spiral drills are used in cutting applications where high cutting speeds are traditionally used, and where the material has a tendency to gall on the drill or otherwise clog the hole, such as aluminum or copper. The point angle is determined by the material the drill will be operating in. Harder materials
•
require a larger point angle, and softer materials require a sharper angle. The correct point angle for the hardness of the material controls wandering, chatter, hole shape, wear rate, and other characteristics. The lip angle determines the amount of support provided to the cutting edge. A greater lip angle will cause the drill to cut more aggressively under the same amount of point pressure as a drill with a smaller lip angle. Both conditions can cause binding, wear, and eventual catastrophic failure of the tool. The proper amount of lip clearance is determined by the point angle. A very acute point angle has more web surface area presented to the work at any one time, requiring an aggressive lip angle, where a flat drill is extremely sensitive to small changes in lip angle due to the small surface area supporting the cutting edges.
•
•
The Mechanic Drills used widely by vendors to further describe the length of the drill itself. The actual length x diameter must be found and published. The Jobber Drills used widely by vendors to further describe the length of the drill itself. The actual length x diameter must be found and published.
Most drills for consumer use have straight shanks. For heavy duty drilling in industry,
Twist drill bit with Morse taper shank Twist drill bit cutting edges drills with tapered shanks are sometimes used.
11/32" (8 mm) drills - long-series morse, plain morse, jobber Long series drills are extended length twist drills. They are not the best tool for drilling deep holes, as they require frequent withdrawal to clear the flutes of swarf and prevent drill breakages. Gun drills are the preferred drills for deep hole drilling.
Gun drill see Gun drill
Center drill and spotting drill
Center drills, Numbers 1 through to 6 Center drill bits are used in metalworking to provide a starting hole for a larger-sized drill bit or to make a conical indentation in the end of a workpiece in which to mount a lathe center. In either use, the name seems apt, as the drill is either establishing the center of a hole or making a conical hole for a lathe center. However, the true purpose of a center drill is the latter task, while the former task is best done with a spotting drill (as explained in detail below). Nevertheless, because of the frequent lumping together of both the terminology and the tool use, suppliers may call center drills combined-drilland-countersinks in order to make unambiguously clear what product is being ordered.
Use in making holes for lathe centers Centre drills are meant to create a conical hole for "between centers" manufacturing processes (typically lathe or cylindrical-grinder work). That is, they provide a location for a (live, dead, or driven) center to locate the part about an axis. A workpiece machined between centers can be safely removed from one process (perhaps turning in a lathe) and set up in a later process (perhaps a grinding operation) with what is often a negligible loss in the co-axiality of features.
Use in spotting hole centers Traditional twist drill bits may tend to wander when started on an unprepared surface. Once a bit wanders off-course it is difficult to bring it back on center. A center drill bit frequently provides a reasonable starting point as it is short and therefore has a reduced tendency to wander when drilling is started. While the above is a common use of center drills, it is a technically-incorrect practice and should not be considered for production use. The correct tool to start a traditionallydrilled hole (a hole drilled by a high-speed steel (HSS) twist drill) is a spotting drill, or a spot drill, as they are referred to in the U.S. The included angle of the spotting drill should be the same as, or greater than, the conventional drill bit so that the drill bit will
then start without undue stress on the drill's corners, which would cause premature failure of the drill and a loss of hole quality. Most modern solid-carbide drills should not be used in conjunction with a spot drill or a center drill. They are specifically designed to start their own hole. Usually, spot drilling will cause premature failure of the carbide drill and a certain loss of hole quality. If it is deemed necessary to chamfer a hole with a spot or center drill when a carbide drill is used, it is best practice to do so after the hole is drilled. Centre drills wander as easily as anything else in hand-held power drills—for such operations, so a center punch is often used to spot the planned hole centre prior to drilling a pilot hole. However, a centre drill works nearly as well as a spotting drill for most rigidly-clamped drilling operations, especially in softer metals such as aluminum and its alloys. The small starting tip has a tendency to break, so it is economical and practical to make the drill bit double-ended.
Core drill
3 fluted core drill as used on castings etc. A core drill bit (as pictured) is used to enlarge an existing hole. The existing hole may be the result of a core from a casting or a stamped (punched) hole. The name of this bit may be somewhat confusing. •
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A diamond core drill bit cuts a cylindrical core, cutting an annulus in the workpiece. The diamond core bit is cylindrical. A core drill bit is named because its first use was in drilling out the hole left by a foundry core, a cylinder placed in a mould for a casting that leaves
an irregular hole in the product. This core drill bit is solid. Core drill bits are similar in appearance to reamers as they have no cutting point or means of starting a hole. They have 3 or 4 flutes which enhances the finish of the hole and ensures the bit cuts evenly. Core drill bits differ from reamers in the amount of material they are intended to remove. A reamer is only intended to enlarge a hole a slight amount which, depending on the reamers size, may be anything from 0.1 millimeter to perhaps a millimeter. A core drill bit may be used to double the size of a hole. Using an ordinary two-flute twist drill to enlarge the hole resulting from a casting core will not produce a clean result, the result will possibly be out of round, off center and generally of poor finish. The two fluted drill also has a tendency to grab on any protuberance (such as casting flash) which may occur in the product.
Left-hand bit
An 1/8in left-hand drill bit Left-hand bits are almost always twist bits and are predominantly used in the repetition engineering industry on screw machines or drilling heads. Left-handed drills allow a machining operation to continue when the spindle either cannot be reversed or where the design of the machine makes it more efficient to run left-handed. With the increased use of the more versatile CNC machines their usage is less common than when specialised machines were required for machining tasks. They may also be used as an aid in the removal of common right-hand screws. Since the rotation of the drill bit is such as it would loosen the screw, using it to drill into the damaged screw head will usually remove the screw, providing the bit "grabs" the damaged material successfully.
Screw extractor
A screw extractor in a T-wrench Another type of left-hand bit is an extraction tool used expressly for removing broken or seized screws, other than by drilling. It has a highly tapered thread structure on it, and is inserted into a drilled hole (of the recommended size) in the damaged screw. If a left hand drill bit is used initially, and the act of drilling the hole does not release the screw, this tool may remove it. In use, the extractor is rotated and the action of the taper and spiral digs into the damaged material causing it to lock tightly and hopefully applies enough pressure to remove the screw. The tool has a tendency to continue winding in while being turned and this may cause the extractor to expand the screw in the hole causing it to bind further, leading to failure of the process. These bits are made of very hard, but brittle, steel, which means they can break off inside the screw if too much force is applied, making the removal much more difficult. Because of this an alternative extractor has four parallel edges, which tends not to self-tighten. Alternatively, the hole can be drilled with successively larger bits until it can be tapped.
Three sizes of damaged screw removal bits square shank, screw extractors
Countersink bit see countersink
Indexable drill Indexable drill bits are primarily used in CNC and other high precision or production equipment, and are the most expensive type of drill bit, costing the most per diameter and length. Like indexable lathe tools and milling cutters, they use replaceable ceramic inserts as a cutting face to alleviate the need for a tool grinder. One insert is responsible for the outer radius of the cut, and another insert is responsible for the inner radius. The tool itself handles the point deformity, as it is a low-wear task. The bit is hardened and coated against wear far more than the average drill bit, as the shank is non-consumable. Almost all indexable drills have multiple coolant channels for prolonged tool life under heavy usage. They are also readily available in odd configurations, such as straight flute, fast spiral, multiflute, and a variety of cutting face geometries. Typically indexable drills are used in holes that are no deeper than about 5 times the drill diameter. They are capable of quite high axial loads and cut very fast.
Spade drill A spade drill is usually a two part drill. The cutting point being removable and usually made of high speed steel. Often spade drills will have coolant lines running through the body. Since the cutting point is removable, one drill can be used for a range of hole sizes. Spade drills are capable of cutting to a depth of about 10 times the drill diameter. Cut diameters are typically in the range of about 3/4" to 3".
Trepan A trepan, sometimes called a BTA Drill (after the Boring and Trepanning Association), is a drill that cuts an annulus and leaves a center core. Trepans usually have multiple carbide inserts and rely on water to cool the cutting tips and to flush chips out of the hole. Trepans are often used to cut large diameters and deep holes. Typical drill diameters are 6" to 14" and hole depth from 12" up to 71 feet.
Ejector drill Used almost exclusively for deep hole drilling of medium to large diameter holes (about 3/4" up to about 4" diameter). An ejector drill uses a specially designed carbide cutter at the point. The drill body is essentially a tube within a tube. Flushing water travels down between the two tubes. Chip removal is back through the center of the drill.
Wood drills Lip and spur drill
10.5 mm Lip and spur bit The lip and spur drill bit is a variation of the twist drill which is optimized for drilling in wood. It is also called the brad point bit or dowelling bit. Conventional twist drill bits do tend to wander when presented to a flat workpiece. For metalwork, this is countered by drilling a pilot hole with a spotting drill. In wood, there is another possible solution, that used in the lip and spur drill. The centre of the drill bit is given not the straight chisel of the twist drill, but a spur with a sharp point and four sharp
corners to cut the wood. The sharp point of the spur simply pushes into the soft wood to keep the drill bit in line. Metals are typically isotropic, and an ordinary twist drill shears the edges of the hole cleanly. Wood drilled across the grain has long strands of wood fibre. These long strands tend to pull out of the wood hole, rather than being cleanly cut at the hole edge. The lip and spur drill bit has the outside corner of the cutting edges leading, so that it cuts the periphery of the hole before the inner parts of the cutting edges plane off the base of the hole. By cutting the periphery first, the lip maximises the chance that the fibres can be cut cleanly, rather than having them pull messily out of the timber. Lip and spur drill bits are also effective in soft plastic. Conventional twist drills in a hand drill, where the hole axis is not maintained throughout the operation, have a tendency to smear the edges of the hole through side friction as the drill vibrates. In metal, the lip and spur drill is confined to drilling only the thinnest and softest sheet metals in a drill press. The drills have an extremely fast cutting tool geometry: no point angle and a large (considering the flat cutting edge) lip angle causes the edges to take a very aggressive cut with relatively little point pressure. This means these drills tend to bind in metal; given a workpiece of sufficient thinness, they have a tendency to punch through and leave the drill's cross-sectional geometry behind. Lip and spur drill bits are ordinarily available in diameters from 3 mm (1/8") to 16 mm (5/8").
Spade bit Spade bits are used for rough boring in wood. They tend to cause splintering when they emerge from the workpiece. They are flat, with a centering point and two cutters. The cutters often are equipped with spurs in an attempt to ensure a cleaner hole. Having small shank diameters relative to their boring diameters, spade bits shanks often have flats forged or ground into them to prevent slipping in drill chucks. Some bits are equipped with long shanks and have a small hole drilled through the flat part, allowing them to be used much like a bell hanger bit. Intended for high speed use, they are used with electric hand drills. They are also known as paddle bits.
Spade bits
Tiny spade bit
Forstner bit
25 mm (1") Forstner bit
Another Forstner bit Forstner bits, named after their inventor, Benjamin Forstner, bore precise, flat-bottomed holes in wood, in any orientation with respect to the wood grain. They can cut on the edge of a block of wood, and can cut overlapping holes. Because of the flat bottom to the hole, they are useful for drilling through veneer already glued to add an inlay. They require great force to push them into the material, so are normally used in drill presses or lathes rather than in portable drills. Unlike most other types of drills, they are not practical to use as hand tools. The bit has a centre point which guides it during the cut (and incidentally spoils the otherwise flat bottom of the hole). The cylindrical cutter around the perimeter shears the wood fibres at the edge of the bore, and also helps guide the bit into the wood precisely. The tool in the image has a total of two cutting edges in this cylinder. Sawtooth Forstner bits are available, with many more cutting edges in the cylinder. These cut faster, but produce a more ragged hole. Forstner bits have radial cutting edges to plane off the material at the bottom of the hole. The bit in the image has two radial edges. Other designs may have more. Forstner bits have no mechanism to clear chips from the hole, and must be pulled out periodically to do this.
Bits are commonly available in sizes from 8 mm (5/16") to 50 mm (2") diameter. Sawtooth bits are available up to 100 mm (4") diameter.
Step bit A step bit, step drill, speed bit, or Unibit is a roughly conical bit with a stair-step profile. Due to their design, a single bit can be used for drilling a wide range of hole sizes. Some bits come to a point and are thus self-starting. The larger-size bits have blunt tips and are used for hole enlarging. They are now available in fractional inch and metric sizes. Step bits are most commonly used in general construction and plumbing. One drillbit can drill the entire range of holes necessary on a countertop, speeding up installation of fixtures. They are most commonly used on softer materials - plywood, particle board, drywall, acrylic, laminate, etc. They can be used on very thin sheetmetal, but metals tend to cause premature drill wear and dulling. A metal hole saw is more appropriate for largehole applications in thicker metals. An additional use of step bits is deburring holes left by other bits, as the sharp increase to the next step size allows the cutting edge to scrape burrs off the entry surface of the workpiece. However, the straight flute is poor at chip ejection, and can cause a burr to be formed on the exit side of the hole, more so than a spiral twist drill turning at high speed. The step bit was invented by Harry C. Oakes of Wyoming, New York in 1971. He received U.S. Patent 3,758,222 for it on 11 September 1973. Introduced by Unibit Corporation in the 1980s (formerly a subsidiary of Petersen Manufacturing Company and now part of Irwin Industrial Tools), step bits have been copied by other manufacturers since the patent expired.
Center bit The center bit is optimised for drilling in wood with a hand brace. Many different designs have been produced. The centre of the bit is a tapered screw thread. This screws into the wood as the drill is turned, and pulls the bit into the wood. There is no need for any force to push the bit into the workpiece, only the torque to turn the bit. This is ideal for a bit for a hand tool. The radial cutting edges remove a slice of wood of thickness equal to the pitch of the central screw for each rotation of the bit. To pull the bit from the hole, either the female thread in the wood workpiece must be stripped, or the rotation of the bit must be reversed. The edge of the bit has a sharpened spur to cut the fibres of the wood, as in the lip and spur drill. A radial cutting edge planes the wood from the base of the hole. In this version, there is minimal or no spiral to remove chips from the hole. The drill must be periodically withdrawn to clear the chips.
Some versions have two spurs. Some have two radial cutting edges. Center bits do not cut well in the end grain of wood. The central screw tends to pull out, or to split the wood along the grain, and the radial edges have trouble cutting through the long wood fibres. Center bits are made of relatively soft steel, and can be sharpened with a file. The drill bit shown was made sometime before 1950, and still worked to drill holes in 2005. It drills a hole 19 mm (3/4 inch) in diameter.
19 mm (3/4 inch) center bit center bit tip detail
Auger bit The cutting principles of the auger bit are the same as those of the center bit above. The auger adds a long deep spiral flute for effective chip removal. Two styles of auger bit are commonly used in hand braces: the Jennings or Jenningspattern bit has a self-feeding screw tip, two spurs and two radial cutting edges. This bit has a double flute starting from the cutting edges, and extending several inches up the shank of the bit, for waste removal. This pattern of bit was developed by Russell Jennings in the mid-19th century. The Irwin or solid-center auger bit is similar, the only difference being that one of the cutting edges has only a "vestigal flute" supporting it, which extends only about 1/2" (12 mm) up the shank before ending. The other flute continues full-length up the shank for waste removal. The Irwin bit may afford greater space for waste removal, greater strength (because the design allows for a center shank of increased size within the flutes, as compared to the Jenning bits), or smaller manufacturing costs. This style of bit was invented in 1884, and the rights sold to Charles Irwin who patented and marketed this pattern the following year. Both styles of auger bits were manufactured by several companies throughout the earlyand mid-20th century, and are still available new from select sources today. The diameter of auger bits for hand braces is commonly expressed by a single number, indicating the size in 16ths of an inch. For example, #4 is 4/16 or 1/4" (6 mm), #6 is 6/16
or 3/8" (9 mm), #9 is 9/16" (14 mm), and #16 is 16/16 or 1" (25 mm). Sets commonly consist of #4-16 or #4-10 bits. The bit shown in the picture is a modern design for use in portable power tools, made in the UK in about 1995. It has a single spur, a single radial cutting edge and a single flute. Similar auger bits are made with diameters from 6 mm (3/16") to 30 mm (1-3/16"). Augers up to 600 mm (2 feet) long are available, where the chip-clearing capability is especially valuable for drilling deep holes.
20 mm (3/4") auger bit for wood
Auger bit tip detail
Gimlet bit The gimlet bit is a very old design. The bit is the same style as that used in the gimlet, a self-contained tool for boring small holes in wood by hand. Since about 1850, gimlets have had a variety of cutter designs, but some are still produced with the original version. The gimlet bit is intended to be used in a hand brace for drilling into wood. It is the usual style of bit for use in a brace for holes below about 7 mm (1/4") diameter. The tip of the gimlet bit acts as a tapered screw, to draw the bit into the wood and to begin forcing aside the wood fibres, without necessarily cutting them. The cutting action occurs at the side of the broadest part of the cutter. Most drills cut the base of the hole. The gimlet bit cuts the side of the hole. The gimlet bit in the photos was made sometime before 1950.
Gimlet bit for wood
Gimlet bit tip detail
Hinge sinker bit
30 mm hinge sinker bit The hinge sinker bit is an example of a custom drill design for a specific application. Many European kitchen cabinets are made from particle board or medium-density fibreboard (MDF) with a laminated plastic veneer. Those types of pressed wood boards are not very strong, and the screws of butt hinges tend to pull out. A specialist hinge has been developed which uses the walls of a 30 mm (1-3/16") diameter hole, bored in the particle board, for support. This is a very common and relatively successful construction method. A Forstner bit could bore the mounting hole for the hinge, but particle board and MDF are very abrasive materials. Softer steel cutting edges soon wear. A tungsten carbide cutter is needed, and making that in the form of a Forstner bit is impractical. So, this special drill is commonly used. It has cutting edges of tungsten carbide brazed to a steel body. A centre spur keeps the bit from wandering.
Adjustable wood bit
An adjustable wood bit meant for use in a brace An adjustable wood bit has a small center pilot bit with an adjustable, sliding cutting edge mounted above it, usually containing a single sharp point at the outside, with a set screw to lock the cutter in position. When the cutting edge is centered on the bit, the hole drilled will be small, and when the cutting edge is slid outwards, a larger hole is drilled. This allows a single drill bit to drill a wide variety of holes, and can take the place of a large, heavy set of different size bits, as well as providing uncommon bit sizes. A ruler or vernier scale is usually provided to allow precise adjustment of the bit size.
These bits are available both in a version similar to an auger bit or brace bit, designed for low speed, high torque use with a brace or other hand drill (pictured to the right), or as a high speed, low torque bit meant for a power drill. While the shape of the cutting edges is different, and one uses screw threads and the other a twist bit for the pilot, the method of adjusting them remains the same.
Other materials Diamond core bit See Diamond core drill The diamond masonry mortar bit is a hybrid drill bit, designed to work as a combination router and drill bit. It consists of a steel shell, with the diamonds embedded in metal segments attached to the cutting edge. These drills are used at relatively low speeds.
Masonry drill The masonry bit shown here is a variation of the twist drill bit. The bulk of the tool is a relatively soft steel, and is machined with a mill rather than ground. An insert of tungsten carbide is brazed into the steel to provide the cutting edges. Masonry bits typically are used with a hammer drill. The bit is both rotated and hammered into the workpiece. The hammering breaks up the masonry at the drill bit tip. The flutes of the drill bit body carry away the dust. Rotating the bit brings the cutting edges onto a fresh portion of the hole bottom with every hammer blow. Masonry bits of the style shown are commonly available in diameters from 5 mm to 40 mm. For larger diameters, core bits are used. Masonry bits up to 1000 mm (39") long can be used with hand-portable power tools, and are very effective for installing wiring and plumbing in existing buildings.
25×500 mm SDS-plus masonry bit
Masonry bit tip
Holesaw Holesaws take the form of a small circular saw with the teeth parallel to the axis of the drill. They can be used on wood, metal and other materials. See main article at Hole saw.
PCB through-hole drill Printed circuit boards are usually made of fiberglass, which due to being highly abrasive, would quickly ruin a normal drill bit, especially given the many hundreds or thousands of holes on most circuit boards. To solve this problem, solid tungsten carbide twist bits are almost always used, which drill quickly through the board while providing a moderately long life. Carbide PCB bits are estimated to outlast high speed steel bits by a factor of ten or more. In industry, virtually all drilling is done by automated machines, and the bits are often automatically replaced by the equipment as they wear, as even with their solid carbide construction, they still have a short lifespan. PCB bits typically mount in a collet rather than a chuck, and come with standard-size shanks, often with pre-installed stops to set them at an exact depth every time when being automatically chucked by the equipment. Due to the high speed these bits are used at (30,000–100,000 RPM or higher is common), their small size, and the brittleness of the material, even the slightest wobble of an operator's hand will shatter one, as will accidental contact with almost any object. Due to their delicate nature, these bits cannot be used in a hand drill, and even most moderately expensive drill presses will have too low a speed and too much chuck wobble to use these bits without breaking them.
Two PCB drill bits.
A box of #76 (0.02in) PCB drill bits.
Installer bit Installer bits are a type of twist drill bit for use with a hand-portable power tool. They are also known as bell-hanger bits or fishing bits. The key distinguishing feature of an installer bit is a transverse hole drilled through the web of the bit near the tip. Once the bit has penetrated a wall, a wire can be threaded through this transverse hole, and the bit pulled back through the drilled hole. The wire can then be used to pull a cable or pipe back through the wall. This is especially helpful where the wall has a large cavity, where threading a fishtape could be difficult. Some installer bits have a transverse hole drilled at the shank end as well. Once a hole has been drilled, the wire can be threaded through the shank end, the bit removed from the chuck, and all pulled forward through the drilled hole. Sinclair Smith of Brooklyn, New York was issued U.S. Patent 597,750 for this invention on January 25, 1898.
Installer bits are available in various materials and styles for drilling wood, masonry and metal. A variant of the installer bit has a very long flexible shaft, up to 72 inches (1.8 m) long in the US, with a small twist bit at the end. The shaft is made of spring steel instead of hardened steel, so it can be flexed while drilling without breaking. This unique design allows the bit to be curved inside walls, for example to drill through studs from a light switch box without needing to remove any material from the wall. These bits usually come with a set of special tools to aim and flex the bit to reach the desired location and angle, although the problem of seeing where the operator is drilling still remains. The flexible variant of the installer bit does not appear to be routinely available in the EU.
An 3/8" (9 mm) x 18" (457 mm) installer bit
Closeup of installer bit
Well drilling bits Main article: Well drilling Different drill bits are used, depending on the material being drilled for the well. There are three main categories: soft, medium and hard formation bits. Soft formation rock bits are used in unconsolidated sands, clays, soft limestone, red beds and shale, etc. Medium formation bits are used in calcites, dolomites, lime stones, and hard shale, while hard formation bits are used in hard shale, calcites, mudstones, cherty limestone and hard and abrasive formations.
Materials for bit construction
Titanium nitride coated twist bit Many different materials are used for or on drill bits, depending on the required application.
Steels Soft low carbon steel bits are used only in wood, as they do not hold an edge well and require frequent sharpening. Working with hardwoods can cause a noticeable reduction in lifespan. They are inexpensive when compared to other tools with a longer life. high Carbon steel bits are made from high carbon steel and are an improvement on plain steel due to the hardening and tempering capabilities of the material. These bits can be used on wood or metal, however they have a low tolerance to excessive heat which causes them to lose their temper, resulting in a soft cutting edge. High speed steel (HSS) is a form of tool steel where the bits are much more resistant to the effect of heat. They can be used to drill in metal, hardwood, and most other materials at greater cutting speeds than carbon steel bits and have largely replaced them in commercial applications. Cobalt steel alloys are variations on high speed steel which have more cobalt in them. Their main advantage is that they hold their hardness at much higher temperatures, so they are used to drill stainless steel and other hard materials. The main disadvantage of cobalt steels is that they are more brittle than standard HSS.
Exotic materials The material referred to as Tungsten carbide is extremely hard, and can drill in virtually all materials while holding an edge longer than other bits. However, due to its high cost and brittleness, it is more frequently used only in smaller pieces screwed or brazed onto the tip of the bit. It is becoming common in job shops to use solid carbide drills, and in certain industries, most notably PCB drills, it has been commonplace for a long time. Polycrystalline diamond (PCD) is among the hardest of all tool materials and is therefore extremely wear resistant. The material consists of a layer of diamond particles, typically about 0.5 mm (0.019") thick, bonded as a sintered mass to a tungsten carbide support. Bits are fabricated using this material by either brazing small segments to the tip of the tool to form the cutting edges, or by sintering PCD into a vein in the tungsten carbide "nib". The nib can later be brazed to a carbide shaft and ground to complex geometries that cause braze failure in the smaller "segments". PCD bits are typically used in the automotive, aerospace, and other industries to drill abrasive aluminum alloys, carbon fiber reinforced plastics and other abrasive materials, or in applications where machine downtime is undesirable.
Coatings Black oxide is an inexpensive black coating. A black oxide coating provides heat resistance and lubricity, as well as corrosion resistance. These result in a longer drill life than the typical uncoated high-speed steel drill. Titanium nitride (TiN) is a very hard ceramic material, and when used to coat a highspeed steel bit (usually twist bits), can extend the cutting life by three or more times. A titanium nitride bit cannot properly be sharpened, as the new edge will not have the coating, and will not have any of the benefits the coating provided. Titanium aluminum nitride (TiAN) is another coating frequently used. It is considered superior to TiN and can extend tool life five or more times. Titanium carbon nitride (TiCN) is another coating and is also superior to TiN. Diamond powder is used as an abrasive, most often for cutting tile, stone, and other very hard materials. Large amounts of heat are generated, and diamond coated bits often have to be water cooled to prevent damage to the bit or the workpiece.
Gears
A gear is a component within a transmission device that transmits rotational force to another gear or device. A gear is different from a pulley in that a gear is a round wheel which has linkages ("teeth" or "cogs") that mesh with other gear teeth, allowing force to be fully transferred without slippage. Depending on their construction and arrangement, geared devices can transmit forces at different speeds, torques, or in a different direction, from the power source. Gears are a very useful simple machine. The most common situation is for a gear to mesh with another gear, but a gear can mesh with any device having compatible teeth, such as linear moving racks. A gear's most important feature is that gears of unequal sizes (diameters) can be combined to produce a mechanical advantage, so that the rotational speed and torque of the second gear are different from that of the first. In the context of a particular machine, the term "gear" also refers to one particular arrangement of gears among other arrangements (such as "first gear"). Such arrangements are often given as a ratio, using the number of teeth or gear diameter as units. The term "gear" is also used in non-geared devices which perform equivalent tasks: "...broadly speaking, a gear refers to a ratio of engine shaft speed to driveshaft speed. Although CVTs change this ratio without using a set of planetary gears, they are still described as having low and high "gears" for the sake of
General The smaller gear in a pair is often called the pinion; the larger, either the gear, or the wheel.
Mechanical advantage The interlocking of the teeth in a pair of meshing gears means that their circumferences necessarily move at the same rate of linear motion (eg., metres per second, or feet per minute). Since rotational speed (eg. measured in revolutions per second, revolutions per minute, or radians per second) is proportional to a wheel's circumferential speed divided by its radius, we see that the larger the radius of a gear, the slower will be its rotational speed, when meshed with a gear of given size and speed. The same conclusion can also be reached by a different analytical process: counting teeth. Since the teeth of two meshing gears are locked in a one to one correspondence, when all of the teeth of the smaller gear have passed the point where the gears meet -- ie., when the smaller gear has made one revolution -- not all of the teeth of the larger gear will have passed that point -the larger gear will have made less than one revolution. The smaller gear makes more revolutions in a given period of time; it turns faster. The speed ratio is simply the reciprocal ratio of the numbers of teeth on the two gears. (Speed A * Number of teeth A) = (Speed B * Number of teeth B) This ratio is known as the gear ratio. The torque ratio can be determined by considering the force that a tooth of one gear exerts on a tooth of the other gear. Consider two teeth in contact at a point on the line
joining the shaft axes of the two gears. In general, the force will have both a radial and a circumferential component. The radial component can be ignored: it merely causes a sideways push on the shaft and does not contribute to turning. The circumferential component causes turning. The torque is equal to the circumferential component of the force times radius. Thus we see that the larger gear experiences greater torque; the smaller gear less. The torque ratio is equal to the ratio of the radii. This is exactly the inverse of the case with the velocity ratio. Higher torque implies lower velocity and vice versa. The fact that the torque ratio is the inverse of the velocity ratio could also be inferred from the law of conservation of energy. Here we have been neglecting the effect of friction on the torque ratio. The velocity ratio is truly given by the tooth or size ratio, but friction will cause the torque ratio to be actually somewhat less than the inverse of the velocity ratio. In the above discussion we have made mention of the gear "radius". Since a gear is not a proper circle but a roughened circle, it does not have a radius. However, in a pair of meshing gears, each may be considered to have an effective radius, called the pitch radius, the pitch radii being such that smooth wheels of those radii would produce the same velocity ratio that the gears actually produce. The pitch radius can be considered sort of an "average" radius of the gear, somewhere between the outside radius of the gear and the radius at the base of the teeth. The issue of pitch radius brings up the fact that the point on a gear tooth where it makes contact with a tooth on the mating gear varies during the time the pair of teeth are engaged; also the direction of force may vary. As a result, the velocity ratio (and torque ratio) is not, actually, in general, constant, if one considers the situation in detail, over the course of the period of engagement of a single pair of teeth. The velocity and torque ratios given at the beginning of this section are valid only "in bulk" -- as long-term averages; the values at some particular position of the teeth may be different. It is in fact possible to choose tooth shapes that will result in the velocity ratio also being absolutely constant -- in the short term as well as the long term. In good quality gears this is usually done, since velocity ratio fluctuations cause undue vibration, and put additional stress on the teeth, which can cause tooth breakage under heavy loads at high speed. Constant velocity ratio may also be desirable for precision in instrumentation gearing, clocks and watches. The involute tooth shape is one that results in a constant velocity ratio, and is the most commonly used of such shapes today.
Comparison with other drive mechanisms The definite velocity ratio which results from having teeth gives gears an advantage over other drives (such as traction drives and V-belts) in precision machines such as watches that depend upon an exact velocity ratio. In cases where driver and follower are in close proximity gears also have an advantage over other drives in the reduced number of parts required; the downside is that gears are more expensive to manufacture and their lubrication requirements may impose a higher operating cost.
The automobile transmission allows selection between gears to give various mechanical advantages.
Spur gears Spur gears are the simplest, and probably most common, type of gear. Their general form is a cylinder or disk. The teeth project radially, and with these "straight-cut gears", the leading edges of the teeth are aligned parallel to the axis of rotation. These gears can only mesh correctly if they are fitted to parallel axles.[2]
Helical gears
Intermeshing gears in motion Unlike most gears, an internal gear (shown here) does not cause direction reversal.
Helical gears from a Meccano construction set. Helical gears offer a refinement over spur gears. The leading edges of the teeth are not parallel to the axis of rotation, but are set at an angle. Since the gear is curved, this angling causes the tooth shape to be a segment of a helix. The angled teeth engage more gradually than do spur gear teeth. This causes helical gears to run more smoothly and quietly than spur gears. Helical gears also offer the possibility of using non-parallel shafts. A pair of helical gears can be meshed in two ways: with shafts oriented at either the sum or the difference of the helix angles of the gears. These configurations are referred to as parallel or crossed, respectively. The parallel configuration is the more mechanically sound. In it, the helices of a pair of meshing teeth meet at a common tangent, and the contact between the tooth surfaces will, generally, be a curve extending
some distance across their face widths. In the crossed configuration, the helices do not meet tangentially, and only point contact is achieved between tooth surfaces. Because of the small area of contact, crossed helical gears can only be used with light loads. Quite commonly, helical gears come in pairs where the helix angle of one is the negative of the helix angle of the other; such a pair might also be referred to as having a right handed helix and a left handed helix of equal angles. If such a pair is meshed in the 'parallel' mode, the two equal but opposite angles add to zero: the angle between shafts is zero -- that is, the shafts are parallel. If the pair is meshed in the 'crossed' mode, the angle between shafts will be twice the absolute value of either helix angle. Note that 'parallel' helical gears need not have parallel shafts -- this only occurs if their helix angles are equal but opposite. The 'parallel' in 'parallel helical gears' must refer, if anything, to the (quasi) parallelism of the teeth, not to the shaft orientation. As mentioned at the start of this section, helical gears operate more smoothly than do spur gears. With parallel helical gears, each pair of teeth first make contact at a single point at one side of the gear wheel; a moving curve of contact then grows gradually across the tooth face. It may span the entire width of the tooth for a time. Finally, it recedes until the teeth break contact at a single point on the opposite side of the wheel. Thus force is taken up and released gradually. With spur gears, the situation is quite different. When a pair of teeth meet, they immediately make line contact across their entire width. This causes impact stress and noise. Spur gears make a characteristic whine at high speeds and can not take as much torque as helical gears because their teeth are receiving impact blows. Whereas spur gears are used for low speed applications and those situations where noise control is not a problem, the use of helical gears is indicated when the application involves high speeds, large power transmission, or where noise abatement is important. The speed is considered to be high when the pitch line velocity (that is, the circumferential velocity) exceeds 5000 ft/min.[3] A disadvantage of helical gears is a resultant thrust along the axis of the gear, which needs to be accommodated by appropriate thrust bearings, and a greater degree of sliding friction between the meshing teeth, often addressed with specific additives in the lubricant.
Double helical gears Double helical gears, invented by André Citroën and also known as herringbone gears, overcome the problem of axial thrust presented by 'single' helical gears by having teeth that set in a 'V' shape. Each gear in a double helical gear can be thought of as two standard, but mirror image, helical gears stacked. This cancels out the thrust since each half of the gear thrusts in the opposite direction. They can be directly interchanged with spur gears without any need for different bearings. Where the oppositely angled teeth meet in the middle of a herringbone gear, the alignment may be such that tooth tip meets tooth tip, or the alignment may be staggered, so that tooth tip meets tooth trough. The latter type of alignment results in what is known as a Wuest type herringbone gear.
With the older method of fabrication, herringbone gears had a central channel separating the two oppositely-angled courses of teeth. This was necessary to permit the shaving tool to run out of the groove. The development of the Sykes gear shaper now makes it possible to have continuous teeth, with no central gap.
Bevel gears
Bevel gear used to lift floodgate by means of central screw. Main article: Bevel gear Bevel gears are essentially conically shaped, although the actual gear does not extend all the way to the vertex (tip) of the cone that bounds it. With two bevel gears in mesh, the vertices of their two cones lie on a single point, and the shaft axes also intersect at that point. The angle between the shafts can be anything except zero or 180 degrees. Bevel gears with equal numbers of teeth and shaft axes at 90 degrees are called miter gears. The teeth of a bevel gear may be straight-cut as with spur gears, or they may be cut in a variety of other shapes. 'Spiral bevel gears' have teeth that are both curved along their (the tooth's) length; and set at an angle, analogously to the way helical gear teeth are set at an angle compared to spur gear teeth. 'Zero bevel gears' have teeth which are curved along their length, but not angled. Spiral bevel gears have the same advantages and disadvantages relative to their straight-cut cousins as helical gears do to spur gears. Straight bevel gears are generally used only at speeds below 5 m/s (1000 ft/min), or, for small gears, 1000 r.p.m.[4]
Crown gear A crown gear A crown gear or contrate gear is a particular form of bevel gear whose teeth project at right angles to the plane of the wheel; in their orientation the teeth resemble the points on a crown. A crown gear can only mesh accurately with another bevel gear, although crown gears are sometimes seen meshing with spur gears. A crown gear is also sometimes meshed with an escapement such as found in mechanical clocks.
Hypoid gears
Main article: Hypoid Hypoid gears resemble spiral bevel gears, except that the shaft axes are offset, not intersecting. The pitch surfaces appear conical but, to compensate for the offset shaft, are in fact hyperboloids of revolution.[citation needed] Hypoid gears are almost always designed to operate with shafts at 90 degrees. Depending on which side the shaft is offset to, relative to the angling of the teeth, contact between hypoid gear teeth may be even smoother and more gradual than with spiral bevel gear teeth. Also, the pinion can be designed with fewer teeth than a spiral bevel pinion, with the result that gear ratios of 60:1 and higher are "entirely feasible" using a single set of hypoid gears.[5]
Worm gear
A worm and gear from a Meccano construction set Main article: Worm gear A worm is a gear that resembles a screw. It is a species of helical gear, but its helix angle is usually somewhat large(ie., somewhat close to 90 degrees) and its body is usually fairly long in the axial direction; and it is these attributes which give it its screw like qualities. A worm is usually meshed with an ordinary looking, disk-shaped gear, which is called the "gear", the "wheel", the "worm gear", or the "worm wheel". The prime feature of a worm-and-gear set is that it allows the attainment of a high gear ratio with few parts, in a small space. Helical gears are, in practice, limited to gear ratios of 10:1 and under; worm gear sets commonly have gear ratios between 10:1 and 100:1, and occasionally 500:1.[6] In worm-and-gear sets, where the worm's helix angle is large, the sliding action between teeth can be considerable, and the resulting frictional loss causes the efficiency of the drive to be usually less than 90 percent, sometimes less than 50 percent, which is far less than other types of gears.[7] The distinction between a worm and a helical gear is made when at least one tooth persists for a full 360 degree turn around the helix. If this occurs, it is a 'worm'; if not, it is a 'helical gear'. A worm may have as few as one tooth. If that tooth persists for several turns around the helix, the worm will appear, superficially, to have more than one tooth, but what one in fact sees is the same tooth reappearing at intervals along the length of the worm. The usual screw nomenclature applies: a one-toothed worm is called "single
thread" or "single start"; a worm with more than one tooth is called "multiple thread" or "multiple start". We should note that the helix angle of a worm is not usually specified. Instead, the lead angle, which is equal to 90 degrees minus the helix angle, is given. In a worm-and-gear set, the worm can always drive the gear. However, if the gear attempts to drive the worm, it may or may not succeed. Particularly if the lead angle is small, the gear's teeth may simply lock against the worm's teeth, because the force component circumferential to the worm is not sufficient to overcome friction. Whether this will happen depends on a function of several parameters; however, an approximate rule is that if the tangent of the lead angle is greater than the coefficient of friction, the gear will not lock.[8] Worm-and-gear sets that do lock in the above manner are called "self locking". The self locking feature can be an advantage, as for instance when it is desired to set the position of a mechanism by turning the worm and then have the mechanism hold that position. An example of this is the tuning mechanism on some types of stringed instruments. If the gear in a worm-and-gear set is an ordinary helical gear only point contact between teeth will be achieved.[9] If medium to high power transmission is desired, the tooth shape of the gear is modified to achieve more intimate contact with the worm thread. A noticeable feature of most such gears is that the tooth tops are concave, so that the gear partly envelopes the worm. A further development is to make the worm concave (viewed from the side, perpendicular to its axis) so that it partly envelopes the gear as well; this is called a cone-drive or Hindley worm.[10]
Helical and Worm Hand, ANSI/AGMA 1012-G05 A right hand helical gear or right hand worm is one in which the teeth twist clockwise as they recede from an observer looking along the axis. The designations, right hand and left hand, are the same as in the long established practice for screw threads, both external and internal. Two external helical gears operating on parallel axes must be of opposite hand. An internal helical gear and its pinion must be of the same hand. A left hand helical gear or left hand worm is one in which the teeth twist counterclockwise as they recede from an observer looking along the axis.[11]
Rack and pinion
Rack and pinion animation Main article: Rack and pinion A rack is a toothed bar or rod that can be thought of as a sector gear with an infinitely large radius of curvature. Torque can be converted to linear force by meshing a rack with a pinion: the pinion turns; the rack moves in a straight line. Such a mechanism is used in automobiles to convert the rotation of the steering wheel into the left-to-right motion of the tie rod(s). Racks also feature in the theory of gear geometry, where, for instance, the tooth shape of an interchangeable set of gears may be specified for the rack (infinite radius), and the tooth shapes for gears of particular actual radii then derived from that.
External vs. internal gears An external gear is one with the teeth formed on the outer surface of a cylinder or cone. Conversely, an internal gear is one with the teeth formed on the inner surface of a cylinder or cone. For bevel gears, an internal gear is one with the pitch angle exceeding 90 degrees.[11]
Parallel axis gears See also Rack railway
Gear nomenclature Gear parts labelled •
Common abbreviations o n. Rotational velocity.
•
•
(Measured, for example, in r.p.m.) o ω Angular velocity. (Radians per unit time.) (1 r.p.m. = π/ 30 radians pe r second.) o N. Number of teeth. Path of contact. The path followed by the point of contact between two meshing gear teeth. Line of action, also called 'Pressure line'. The line along which the force between two meshing gear teeth is directed. It has the same direction as the force vector. In general, the line of action changes from moment to moment during the period of engagement of a pair of teeth. For involute gears, however, the tooth-to-tooth force is always directed along the same line -- that is, the line of action is constant. this implies that for involute gears the path of contact is also a straight line, coincident with the line of action -- as is indeed the case.[12]
•
•
•
•
•
•
Axis. The axis of revolution of the gear; center line of the shaft. Pitch point (p). The point where the line of action crosses a line joining the two gear axes. Pitch circle. A circle, centered on and perpendicular to the axis, and passing through the pitch point. Sometimes also called the 'pitch line', although it is a circle. Pitch diameter (D). Diameter of a pitch circle. Equal to twice the perpendicular distance from the axis to the pitch point. The nominal gear size is usually the pitch diameter. Operating pitch diameters. The pitch diameters determined from the number of teeth and the center distance at which gears operate. [11] Example for pinion: Pitch surface. For cylindrical gears, this is the cylinder formed by projecting a pitch circle in the axial direction. More generally, it is the surface formed by the sum of all the pitch circles as one
•
•
•
•
•
•
moves along the axis. Eg., for bevel gears it is a cone. Angle of action. Angle with vertex at the gear center, one leg on the point where mating teeth first make contact, the other leg on the point where they disengage. Arc of action. The segment of a pitch circle subtended by the angle of action. Pressure angle (ø). The complement of the angle between the direction that the teeth exert force on each other, and the line joining the centers of the two gears. For involute gears, the teeth always exert force along the line of action, which, for involute gears, is a straight line; and thus, for involute gears, the pressure angle is constant. Outside diameter (Do). Diameter of the gear, measured from the tops of the teeth. Root diameter. Diameter of the gear, measured from the base of the tooth space. Addendum (a). The radial distance from the pitch surface to
•
•
the outermost point of the tooth. a = (Do - D) / 2. Dedendum (b). The radial distance from the depth of the tooth trough to the pitch surface. b = (D - root diamete r) / 2. Whole depth (ht). Whole depth (tooth depth) is the total depth of a tooth space, equal to addendum plus dedendum, also equal to working depth plus clearance. [11]
•
•
•
•
Clearance. Clearance is the distance between the root circle of a gear and the addendum circle of its mate.[11] Working depth. Working depth is the depth of engagement of two gears, that is, the sum of their operating addendums.[11] Circular pitch (p). The distance from one face of a tooth to the corresponding face of an adjacent tooth on the same gear, measured along the pitch circle. Diametral pitch (Pd). The ratio of the number of teeth to the pitch diameter. Eg., could be
•
•
•
•
•
measured in teeth per inch or teeth per centimeter. Base circle. Applies only to involute gears, where the tooth profile is the involute of the base circle. The radius of the base circle is somewhat smaller than that of the pitch circle. Base pitch (pb). Applies only to involute gears. It is the distance from one face of a tooth to the corresponding face of an adjacent tooth on the same gear, measured along the base circle. Sometimes called the 'normal pitch'. Interference. Contact between teeth other than at the intended parts of their surfaces. Interchangeable set. A set of gears, any of which will mate properly with any other. Helical Gears: o Helix angle (ψ). The angle between a tangent to the helix and the gear axis. Is zero in the limiting case
•
of a spur gear. o Normal circular pitch (pn). Circular pitch in the plane normal to the teeth. o Transverse circular pitch (p). Circular pitch in the plane of rotation of the gear. Sometimes just called "circular pitch". pn = p cos(ψ). o Several other helix parameters can be viewed either in the normal or transverse planes. The subscript " n " usually indicates the normal. Worm gears: o Lead. The distance from any point on a thread to the correspondin g point on the next turn of the same thread, measured
o
o
o
parallel to the axis. Linear pitch (p). The distance from any point on a thread to the correspondin g point on the adjacent thread, measured parallel to the axis. For a single-thread worm, lead and linear pitch are the same. Lead angle (λ). The angle between a tangent to the helix and a plane perpendicular to the axis. Note that it is the complement of the helix angle which isusually given for helical gears. Pitch diameter (Dw). Same as described earlier in this list. Note that for a worm it is still measured in a
o
plane perpendicular to the gear axis, not a tilted plane. Subscipt " w " denotes the worm, " g " denotes the gear.
Tooth contact nomenclature Point of contact
Path of Action, ANSI/AGMA 1012-G05 A point of contact is any point at which two tooth profiles touch each other.
Line of contact
Line of Contact, ANSI/AGMA 1012-G05 A line of contact is a line or curve along which two tooth surfaces are tangent to each other.
Path of action The path of action is the locus of successive contact points between a pair of gear teeth, during the phase of engagement. For conjugate gear teeth, the path of action passes through the pitch point. It is the trace of the surface of action in the plane of rotation.
Line of action
Line of Action, ANSI/AGMA 1012-G05 The line of action is the path of action for involute gears. It is the straight line passing through the pitch point and tangent to both base circles.
Surface of action The surface of action is the imaginary surface in which contact occurs between two engaging tooth surfaces. It is the summation of the paths of action in all sections of the engaging teeth.
Plane of action
Plane of Action, ANSI/AGMA 1012-G05 The plane of action is the surface of action for involute, parallel axis gears with either spur or helical teeth. It is tangent to the base cylinders.
Zone of action (contact zone)
Zone of Action, ANSI/AGMA 1012-G05 Zone of action (contact zone) for involute, parallel-axis gears with either spur or helical teeth, is the rectangular area in the plane of action bounded by the length of action and the effective face width.
Path of contact
Lines of Contact (helical gear), ANSI/AGMA 1012-G05 The path of contact is the curve on either tooth surface along which theoretical single point contact occurs during the engagement of gears with crowned tooth surfaces or gears that normally engage with only single point contact.
Length of action
Length of Action, ANSI/AGMA 1012-G05
Length of action is the distance on the line of action through which the point of contact moves during the action of the tooth profile.
Arc of action, Qt Arc of action is the arc of the pitch circle through which a tooth profile moves from the beginning to the end of contact with a mating profile.
Arc of approach, Qa
Arc of Action, ANSI/AGMA 1012-G05 Arc of approach is the arc of the pitch circle through which a tooth profile moves from its beginning of contact until the point of contact arrives at the pitch point.
Arc of recess, Qr Arc of recess is the arc of the pitch circle through which a tooth profile moves from contact at the pitch point until contact ends.
Contact ratio, mc, ε Contact ratio in general is the number of angular pitches through which a tooth surface rotates from the beginning to the end of contact.
Transverse contact ratio, mp, εα Transverse contact ratio is the contact ratio in a transverse plane. It is the ratio of the angle of action to the angular pitch. For involute gears it is most directly obtained as the ratio of the length of action to the base pitch.
Face contact ratio, mF, εβ Face contact ratio is the contact ratio in an axial plane, or the ratio of the face width to the axial pitch. For bevel and hypoid gears it is the ratio of face advance to circular pitch.
Total contact ratio, mt, εγ Total contact ratio is the sum of the transverse contact ratio and the face contact ratio. εγ = εα + εβ mt = mp + mF
Modified contact ratio, mo Modified contact ratio for bevel gears is the square root of the sum of the squares of the transverse and face contact ratios.
Limit diameter
Limit Diameter, ANSI/AGMA 1012-G05 Limit diameter is the diameter on a gear at which the line of action intersects the maximum (or minimum for internal pinion) addendum circle of the mating gear. This is also referred to as the start of active profile, the start of contact, the end of contact, or the end of active profile.
Start of active profile (SAP) The start of active profile is the intersection of the limit diameter and the involute profile.
Face advance
Face Advance, ANSI/AGMA 1012-G05 Face advance is the distance on a pitch circle through which a helical or spiral tooth moves from the position at which contact begins at one end of the tooth trace on the pitch surface to the position where contact ceases at the other end.
Backlash Backlash is the error in motion that occurs when gears change direction. It exists because there is always some gap between the tailing face of the driving tooth and the leading face of the tooth behind it on the driven gear, and that gap must be closed before force can be transferred in the new direction. The term "backlash" can also be used to refer to the size of the gap, not just the phenomenon it causes; thus, one could speak of a pair of gears as having, for example, "0.1 mm of backlash." A pair of gears could be designed to have zero backlash, but this would presuppose perfection in manufacturing, uniform thermal expansion characteristics throughout the system, and no lubricant. Therefore, gear pairs are designed to have some backlash. It is usually provided by reducing the tooth thickness of each gear by half the desired gap distance. In the case of a large gear and a small pinion, however, the backlash is usually taken entirely off the gear and the pinion is given full sized teeth. Backlash can also be provided by moving the gears farther apart. For situations, such as instrumentation and control, where precision is important, backlash can be minimised through one of several techniques. For instance, the gear can be split along a plane perpendicular to the axis, one half fixed to the shaft in the usual manner, the other half placed alongside it, free to rotate about the shaft, but with springs between the two halves providing relative torque between them, so that one achieves, in effect, a single gear with expanding teeth. Another method involves tapering the teeth in the axial direction and providing for the gear to be slid in the axial direction to take up slack.
Epicyclic gearing Main article: epicyclic gearing In an ordinary gear train, the gears rotate but their axes are stationary. An epicyclic gear train is one in which one or more of the axes also moves. Examples are the sun and planet
gear system invented by the company of James Watt, in which the axis of the planet gear revolves around the central sun gear; and the differential gear system used to drive the wheels of automobiles, in which the axis of the central bevel pinion is turned "end over end" by the ring gear, the drive to the wheels being taken off by bevel gears meshing with the central bevel pinion. With the differential gearing, the sum of the two wheel speeds is fixed, but how it is divided between the two wheels is undetermined, so the outer wheel can run faster and the inner wheel slower on corners.
Shifting of gears In some machines (e.g., automobiles) it is necessary to alter the gear ratio to suit the task. There are several methods of accomplishing this. For example: • • •
•
• •
Manual transmission Automatic gearbox Derailleur gears which are actually sprockets in combination with a roller chain Hub gears (also called epicyclic gearing or sun-andplanet gears) Continuously variable transmission Transmission (mechanics)
There are several outcomes of gear shifting in motor vehicles. In the case of air pollution emissions, there are higher pollutant emissions generated in the lower gears, when the engine is working harder than when higher gears have been attained. In the case of vehicle noise emissions, there are higher sound levels emitted when the vehicle is engaged in lower gears. This fact has been utilized in analyzing vehicle generated sound since the late 1960s, and has been incorporated into the simulation of urban roadway noise and corresponding design of urban noise barriers along roadways.[13]
Tooth profile
Profile of a Spur Gear, ANSI/AGMA 1012-G05 A profile is one side of a tooth in a cross section between the outside circle and the root circle. Usually a profile is the curve of intersection of a tooth surface and a plane or surface normal to the pitch surface, such as the transverse, normal, or axial plane. The fillet curve (root fillet) is the concave portion of the tooth profile where it joins the bottom of the tooth space.2 As mentioned near the beginning of the article, the attainment of a non fluctuating velocity ratio is dependent on the profile of the teeth. Friction and wear between two gears is also dependent on the tooth profile. There are a great many tooth profiles that will give a constant velocity ratio, and in many cases, given an arbitrary tooth shape, it is possible to develop a tooth profile for the mating gear that will give a constant velocity ratio. However, two constant velocity tooth profiles have been by far the most commonly used in modern times. They are the cycloid and the involute. The cycloid was more common until the late 1800s; since then the involute has largely superseded it, particularly in drive train applications. The cycloid is in some ways the more interesting and flexible shape; however the involute has two advantages: it is easier to manufacture, and it permits the center to center spacing of the gears to vary over some range without ruining the constancy of the velocity ratio. Cycloidal gears only work properly if the center spacing is exactly right. Cycloidal gears are still used in mechanical clocks.
Undercut
Undercut, ANSI/AGMA 1012-G05 Undercut is a condition in generated gear teeth when any part of the fillet curve lies inside of a line drawn tangent to the working profile at its point of juncture with the fillet. Undercut may be deliberately introduced to facilitate finishing operations. With undercut the fillet curve intersects the working profile. Without undercut the fillet curve and the working profile have a common tangent.
Pitch
Pitch, ANSI/AGMA 1012-G05 Pitch is the distance between a point on one tooth and the corresponding point on an adjacent tooth.[11] It is a dimension measured along a line or curve in the transverse, normal, or axial directions. The use of the single word “pitch” without qualification may be ambiguous, and for this reason it is preferable to use specific designations such as transverse circular pitch, normal base pitch, axial pitch.
Circular pitch, p Circular pitch is the arc distance along a specified pitch circle or pitch line between corresponding profiles of adjacent teeth.
Transverse circular pitch, pt
Tooth Pitch, ANSI/AGMA 1012-G05 Transverse circular pitch is the circular pitch in the transverse plane.
Normal circular pitch, pn, pe Normal circular pitch is the circular pitch in the normal plane, and also the length of the arc along the normal pitch helix between helical teeth or threads.
Axial pitch, px
Base Pitch Relationships, ANSI/AGMA 1012-G05 Axial pitch is linear pitch in an axial plane and in a pitch surface. In helical gears and worms, axial pitch has the same value at all diameters. In gearing of other types, axial pitch may be confined to the pitch surface and may be a circular measurement. The term axial pitch is preferred to the term linear pitch. The axial pitch of a helical worm and the circular pitch of its wormgear are the same.
Normal base pitch, pN, pbn Normal base pitch in an involute helical gear is the base pitch in the normal plane. It is the normal distance between parallel helical involute surfaces on the plane of action in the normal plane, or is the length of arc on the normal base helix. It is a constant distance in any helical involute gear.
Transverse base pitch, pb, pbt
Principal Pitches, ANSI/AGMA 1012-G05 Base pitch in an involute gear is the pitch on the base circle or along the line of action. Corresponding sides of involute gear teeth are parallel curves, and the base pitch is the constant and fundamental distance between them along a common normal in a transverse plane.
Diametral pitch (transverse), Pd Diametral pitch (transverse) is the ratio of the number of teeth to the standard pitch diameter in inches.
Normal diametral pitch, Pnd Normal diametral pitch is the value of diametral pitch in a normal plane of a helical gear or worm.
Angular pitch, θN, τ Angular pitch is the angle subtended by the circular pitch, usually expressed in radians. τ = degrees or radians
Cage gear The cage gear, also called lantern gear or lantern pinion, has been used for centuries. Its teeth are cylindrical rods, parallel to the axle and arranged in a circle around it, much as the bars on a round bird cage or lantern. The assembly is held together by disks at either end into which the tooth rods and axle are set.
Gear materials Numerous nonferrous alloys, cast irons, powder-metallurgy and even plastics are used in the manufacture of gears. However steels are most commonly used because of their high strength to weight ratio and low cost. Plastic is commonly used where cost or weight is a concern. A properly designed plastic gear can replace steel in many cases; It often has desirable properties. They can tolerate dirt, low speed meshing, and "skipping" quite well. Manufacturers have employed plastic to make consumer items affordable. This includes copy machines, optical storage devices, VCRs, cheap dynamos, consumer audio equipment, servo motors, and printers.
Tooth thickness Circular thickness
Tooth Thickness, ANSI/AGMA 1012-G05 Circular thickness is the length of arc between the two sides of a gear tooth, on the specified datum circle.
Transverse circular thickness
Thickness Relationships, ANSI/AGMA 1012-G05 Transverse circular thickness is the circular thickness in the transverse plane.
Normal circular thickness Normal circular thickness is the circular thickness in the normal plane. In a helical gear it may be considered as the length of arc along a normal helix.
Axial thickness Axial thickness in helical gears and worms is the tooth thickness in an axial cross section at the standard pitch diameter.
Base circular thickness Base circular thickness in involute teeth is the length of arc on the base circle between the two involute curves forming the profile of a tooth.
Normal chordial thickness
Chordial Thickness, ANSI/AGMA 1012-G05 Chordal thickness is the length of the chord that subtends a circular thickness arc in the plane normal to the pitch helix. Any convenient measuring diameter may be selected, not necessarily the standard pitch diameter.
Chordial addendum (chordial height) Chordal addendum (chordal height) is the height from the top of the tooth to the chord subtending the circular thickness arc. Any convenient measuring diameter may be selected, not necessarily the standard pitch diameter.
Profile shift The profile shift is the displacement of the basic rack datum line from the reference cylinder, made non-dimensional by dividing by the normal module. It is used to specify the tooth thickness, often for zero backlash.
Rack shift
Tooth Thickness Measurement Over Pins, ANSI/AGMA 1012-G05 The rack shift is the displacement of the tool datum line from the reference cylinder, made non-dimensional by dividing by the normal module. It is used to specify the tooth thickness.
Measurement over pins Measurement over pins is the measurement of the distance taken over a pin positioned in a tooth space and a reference surface. The reference surface may be the reference axis of the gear, a datum surface or either one or two pins positioned in the tooth space or spaces opposite the first. This measurement is used to determine tooth thickness.
Span measurement
Span Measurement, ANSI/AGMA 1012-G05 Span measurement is the measurement of the distance across several teeth in a normal plane. As long as the measuring device has parallel measuring surfaces that contact on an unmodified portion of the involute, the measurement will be along a line tangent to the base cylinder. It is used to determine tooth thickness.
Modified addendum teeth Teeth of engaging gears, one or both of which have non-standard addendum.
Full-depth teeth Full-depth teeth are those in which the working depth equals 2.000 divided by the normal diametral pitch.
Stub teeth
Long and Short Addendum Teeth, ANSI/AGMA 1012-G05 Stub teeth are those in which the working depth is less than 2.000 divided by the normal diametral pitch.
Equal addendum teeth Equal addendum teeth are those in which two engaging gears have equal addendums.
Long and short-addendum teeth Long and short addendum teeth are those in which the addendums of two engaging gears are unequal "Worm gear" redirects here. For the computing term "WORM drive", see Write Once Read Many.
Worm and worm gear A worm drive is a gear arrangement in which a worm (which is a gear in the form of a screw) meshes with a worm gear (which is similar in appearance to a spur gear, and is also called a worm wheel). The terminology is often confused by imprecise use of the term worm gear to refer to the worm, the worm gear, or the worm drive as a unit. Like other gear arrangements, a worm drive can reduce rotational speed or allow higher torque to be transmitted. The image shows a section of a gear box with a bronze worm gear being driven by a worm. A worm is an example of a screw, one of the six simple machines.
Applications Worm drives are a compact, efficient [efficient only in terms of volume; heat friction issues cause vast inefficiencies ranging up to 50%] means of substantially decreasing speed and increasing torque. Small electric motors are generally high-speed and lowtorque; the addition of a worm drive increases the range of applications that it may be suitable for, especially when the worm drive's compactness is considered.
Worm drives are used in presses, in rolling mills, in conveying engineering, in mining industry machines, and on rudders. In addition, milling heads and rotary tables are positioned using high-precision duplex worm drives with adjustable backlash. In the era of sailing ships, the introduction of a worm drive to control the rudder was a significant advance. Prior to its introduction, a rope drum drive was used to control the rudder, and rough seas could cause substantial force to be applied to the rudder, often requiring several men to steer the vessel, with some drives having two large-diameter wheels to allow up to four crewmen to operate the rudder.
A worm drive controlling a gate. The position of the gate will not change after being set Worm drives have been used in a few automotive differentials. The worm gear carries the differential gearing. This protects the vehicle against rollback. This has largely fallen from favour due to the higher-than-necessary reduction ratios. The exception to this is the Torsen differential, which uses worms and planetary worm gears in place of the bevel gearing of conventional open differentials. Torsen differentials are most prominently featured in the HMMWV and some commercial Hummer vehicles, and as a center differential in some all wheel drive systems, such as Audi's quattro. Very heavy trucks, such as those used to carry aggregates, often use a worm gear differential for strength. The worm drive is not as efficient as a hypoid gear, and such trucks invariably have a very large differential housing, with a correspondingly large volume of gear oil, to absorb and dissipate the heat created. Worm drives are used as the tuning mechanism for many musical instruments, including guitars, double-basses, mandolins and bouzoukis, although not banjos, which use planetary gears or friction pegs. A worm drive tuning device is called a machine head. Plastic worm drives are often used on small battery-operated electric motors, to provide an output with a lower angular velocity (fewer revolutions per minute) than that of the motor, which operates best at a fairly high speed. This motor-worm-gear drive system is often used in toys and other small electrical devices. A worm drive is used on jubilee-type hose clamps or jubilee clamps; the tightening screw has a worm thread which engages with the slots on the clamp band.
WELCOME TO THE WORLD OF THE MICROCONTROLLERS.
Look around. Notice the smart “intelligent” systems? Be it the T.V, washing machines, video games, telephones, automobiles, aero planes, power systems, or any application having a LED or a LCD as a user interface, the control is likely to be in the hands of a micro controller! Measure and control, that’s where the micro controller is at its best. Micro controllers are here to stay. Going by the current trend, it is obvious that micro controllers will be playing bigger and bigger roles in the different activities of our lives. So where does this scenario leave us? Think about it…… The world of Micro controllers What is the primary difference between a microprocessor and a micro controller? Unlike the microprocessor, the micro controller can be considered to be a true “Computer on a chip”. In addition to the various features like the ALU, PC, SP and registers found on a microprocessor, the micro controller also incorporates features like the ROM, RAM, Ports, timers, clock circuits, counters, reset functions etc.
While the microprocessor is more a general-purpose device, used for read, write and calculations on data, the micro controller, in addition to the above functions also controls the environment. We have used a whole lot of technical terms already! Don’t get worried about the meanings at this point. We shall understand these terms as we proceed further For now just be aware of the fact, that all these terms literally mean what they say. Bits and Bytes Before starting on the 8051, here is a quick run through on the bits and bytes. The basic unit of data for a computer is a bit. Four bits make a nibble. Eight bits or two nibbles make a byte. Sixteen bits or four nibbles or two bytes make a word. 1024 bytes make a kilobyte or 1KB, and 1024 KB make a Mega Byte or 1MB. Thus when we talk of an 8-bit register, we mean the register is capable of holding data of 8 bits only. The 8051
The 8051 developed and launched in the early 80`s, is one of the most popular micro controller in use today. It has a reasonably large amount of built in ROM and RAM. In addition it has the ability to access external memory. The generic term `8x51` is used to define the device. The value of x defining the kind of ROM, i.e. x=0, indicates none, x=3, indicates mask ROM, x=7, indicates EPROM and x=9 indicates EEPROM or Flash. A note on ROM The early 8051, namely the 8031 was designed without any ROM. This device could run only with external memory connected to it. Subsequent developments lead to the development of the PROM or the programmable ROM. This type had the disadvantage of being highly unreliable. The next in line, was the EPROM or Erasable Programmable ROM. These devices used ultraviolet light erasable memory cells. Thus a program could be loaded, tested and erased using ultra violet rays. A new program could then be loaded again. An improved EPROM was the EEPROM or the electrically erasable PROM. This does not require ultra violet rays, and memory can be cleared using circuits within the chip itself. Finally there is the FLASH, which is an improvement over the EEPROM. While the terms EEPROM and flash are sometimes used interchangeably,
the difference lies in the fact that flash erases the complete memory at one stroke, and not act on the individual cells. This results in reducing the time for erasure. Understanding the basic features of the 8051 core Let’s now move on to a practical example. We shall work on a simple practical application and using the example as a base, shall explore the various features of the 8051 microcontroller. Consider an electric circuit as follows,
The positive side (+ve) of the battery is connected to one side of a switch. The other side of the switch is connected to a bulb or LED (Light Emitting Diode). The bulb is then connected to a resistor, and the other end of the resistor is connected to the negative (-ve) side of the battery. When the switch is closed or ‘switched on’ the bulb glows. When the switch is open or ‘switched off’ the bulb goes off If you are instructed to put the switch on and off every 30 seconds, how would you do it? Obviously you would keep looking at your watch and
every time the second hand crosses 30 seconds you would keep turning the switch on and off. Imagine if you had to do this action consistently for a full day. Do you think you would be able to do it? Now if you had to do this for a month, a year?? No way, you would say! The next step would be, then to make it automatic. This is where we use the Microcontroller. But if the action has to take place every 30 seconds, how will the microcontroller keep track of time? Execution time Look at the following instruction, clr p1.0 This is an assembly language instruction. It means we are instructing the microcontroller to put a value of ‘zero’ in bit zero of port one. This instruction is equivalent to telling the microcontroller to switch on the bulb. The instruction then to instruct the microcontroller to switch off the bulb is, Setb p1.0 This instructs the microcontroller to put a value of ‘one’ in bit zero of port
one. Don’t worry about what bit zero and port one means. We shall learn it in more detail as we proceed. There are a set of well defined instructions, which are used while communicating with the microcontroller. Each of these instructions requires a standard number of cycles to execute. The cycle could be one or more in number. How is this time then calculated? The speed with which a microcontroller executes instructions is determined by what is known as the crystal speed. A crystal is a component connected externally to the microcontroller. The crystal has different values, and some of the used values are 6MHZ, 10MHZ, and 11.059 MHz etc. Thus a 10MHZ crystal would pulse at the rate of 10,000,000 times per second. The time is calculated using the formula No of cycles per second = Crystal frequency in HZ / 12. For a 10MHZ crystal the number of cycles would be, 10,000,000/12=833333.33333 cycles. This means that in one second, the microcontroller would execute
833333.33333 cycles. Therefore for one cycle, what would be the time? Try it out. The instruction clr p1.0 would use one cycle to execute. Similarly, the instruction setb p1.0 also uses one cycle. So go ahead and calculate what would be the number of cycles required to be executed to get a time of 30 seconds! Getting back to our bulb example, all we would need to do is to instruct the microcontroller to carry out some instructions equivalent to a period of 30 seconds, like counting from zero upwards, then switch on the bulb, carry out instructions equivalent to 30 seconds and switch off the bulb. Just put the whole thing in a loop, and you have a never ending on-off sequence. Simple isn’t it? Let us now have a look at the features of the 8051 core, keeping the above example as a reference, 1. 8-bit CPU.( Consisting of the ‘A’ and ‘B’ registers) Most of the transactions within the microcontroller are carried out through the ‘A’ register, also known as the Accumulator. In addition all arithmetic
functions are carried out generally in the ‘A’ register. There is another register known as the ‘B’ register, which is used exclusively for multiplication and division. Thus an 8-bit notation would indicate that the maximum value that can be input into these registers is ‘11111111’. Puzzled? The value is not decimal 111, 11,111! It represents a binary number, having an equivalent value of ‘FF’ in Hexadecimal and a value of 255 in decimal. We shall read in more detail on the different numbering systems namely the Binary and Hexadecimal system in our next module. 2. 4K on-chip ROM Once you have written out the instructions for the microcontroller, where do you put these instructions? Obviously you would like these instructions to be safe, and not get deleted or changed during execution. Hence you would load it into the ‘ROM’ The size of the program you write is bound to vary depending on the application, and the number of lines. The 8051 microcontroller gives you space to load up to 4K of program size into the internal ROM. 4K, that’s all? Well just wait. You would be surprised at the amount of stuff you can load in this 4K of space.
Of course you could always extend the space by connecting to 64K of external ROM if required. 3. 128 bytes on-chip RAM This is the space provided for executing the program in terms of moving data, storing data etc. 4. 32 I/O lines. (Four- 8 bit ports, labeled P0, P1, P2, P3) In our bulb example, we used the notation p1.0. This means bit zero of port one. One bit controls one bulb. Thus port one would have 8 bits. There are a total of four ports named p0, p1, p2, p3, giving a total of 32 lines. These lines can be used both as input or output. 5. Two 16 bit timers / counters. A microcontroller normally executes one instruction at a time. However certain applications would require that some event has to be tracked independent of the main program. The manufacturers have provided a solution, by providing two timers. These timers execute in the background independent of the main program. Once the required time has been reached, (remember the time calculations
described above?), they can trigger a branch in the main program. These timers can also be used as counters, so that they can count the number of events, and on reaching the required count, can cause a branch in the main program. 6. Full Duplex serial data receiver / transmitter. The 8051 microcontroller is capable of communicating with external devices like the PC etc. Here data is sent in the form of bytes, at predefined speeds, also known as baud rates. The transmission is serial, in the sense, one bit at a time 7. 5- interrupt sources with two priority levels (Two external and three internal) During the discussion on the timers, we had indicated that the timers can trigger a branch in the main program. However, what would we do in case we would like the microcontroller to take the branch, and then return back to the main program, without having to constantly check whether the required time / count has been reached? This is where the interrupts come into play. These can be set to either the timers, or to some external events. Whenever the background program has reached the required criteria in terms of time or count or an external event, the branch is taken, and on completion of the branch, the control returns to
the main program. Priority levels indicate which interrupt is more important, and needs to be executed first in case two interrupts occur at the same time. 8. On-chip clock oscillator. This represents the oscillator circuits within the microcontroller. Thus the hardware is reduced to just simply connecting an external crystal, to achieve the required pulsing rate.
Program Code
org 0000h PUSH ACC PUSH PSW MOV TH0,#$FF MOV TL0,#$00 jnb p1.0,f1 jnb p1.1,b1 jnb p1.2,axis1
reload timer 0 for ms
jnb p1.3,axis2 jnb p1.4,up jnb p1.5,down jnb p1.6,jaw1 jnb p1.7,jaw2
f1: CLR A MOV A,#01000000h acall start acall delay
ret b1: CLR A MOV A,#10000000h acall start acall delay
ret
axis1: CLR A MOV A,#00010000h acall start acall delay
ret
axis2: CLR A MOV A,#00100000h acall start acall delay
ret up: CLR A MOV A,#00000100h acall start acall delay
ret
down: CLR A MOV A,#00001000h acall start acall delay
ret jaw1: CLR A MOV A,#00000001h acall start acall delay
ret
jaw2: clr A mov A,#00000010h
acall start mov p1,A lcall dealy
ret start: Mov p3,A ret
delay: here2: mov r2,#50 here : mov r3,#255 djnz r3,here djnz r2,here2 ret end nop nop
nop nop nop
Requirements: • Equipment:Filer,Cutter,Soldering Iron, • Hardware:Wood pieces- 1.5” * 5” Stepper Motors Screws 1” Warshels Nut 1.5” Metallic sheet Electronics Components needed: LM7805 IN4007- rectifier PC 817- 6nos. Transistor bc548 Bc 558 Resistor 1k, 10k, 4.7k, 470E Capacitor- 10µf, 1000µf, 470µf, 22pf Crystal 11.0592 MHz IC base 40 pin Transformer- 12-0-12v
keil software to make .hex file from .asm file
Uploader software to program IC
PROCREDURE TO MAKE PROJECT:1. IDEA OF PROJECT In this stage student select the topic of the project of the project. It’s the main stage of project work.its the area where talented students shows their innovative ideas. Innovative students make project with a new idea then others. We selected this project because we want to do something in with our own hands. We use main electronics components uded in the industry. First of all we selected the GSM based project. Then we drop idea because there was little bit practical electronics to learn and mobile companies already providing those facility. 2. STUDY MATERIAL AND CIRCUIT DIAGRAM In this section we collected the study material. We searches about our project on google.com,www.yahoo.com,www.msn.com and www.ludhianaprojects.com. But we find many circuits and theory materials for our project. We were not sure about the circuits. Because circuit available on the site were provided by students. So we can really on them. Then we saw www.ludhianaprojects.com a project help provider site. Its help us lot. They helped us lot in our project. We find the circuit of our project in that site. 3. Trail TESTING OF MAIN CIRCUIT- Then we collect the components of project. It was not a easy task. Because no shop in our area have all the components. Then after collection of components we test the circuit on bread board - step by step. Because we want to sure about the circuit. We checked it in different steps beacuuse it was a big project and was not possible to check it in a single step. 4. PCB DESIGNING - After Testing of circuite sure about the circuit. First of all we designed the layout of PCB . Then we made a screen . After that we mark the layout on clad board with the help of paint and screen. Then we dip that painted PCB in Ferric chloride solution. After that we drill holes in PCB. Then we washed PCB with Isopropyl solution.
5. COMPONENT MOUNTING- We kept the hole size from 0.8mm yo 1 mm for leads of components. Then we insert components according ton their pitches. 6. SODERING- Afgter mounting components we solder the components ane by one. We kept the temperature of iron at 250 degree to 400 degree. Because above this temperature it can damage to component. We used general iron available in the market of siron company. Its temperature was nearly 350 degree acc to company specifications. We used soldering wire of 22 gauge with flux inbuilt. 7. FINAL TESTING- After that we test the circuit step by step . and insert the ICs after testing the one portion of the circuit an then after other step by step. Its was tough work we tested voltage across the compents with erepect to ground. And current in series. 8. TROUBLSHOOTING- Then we tried to troubleshoot the errors in the project.
Applications For industrial automation For robotics For biomedical machines For military application For construction Bibliography:http://www.ecawa.asn.au/home/jfuller/steppers.html www.ludhianaprojects.com/mechanical.html
