LATHE MACHINE 1)Definition : Lathe machine is the ssingle ingle most versatif machine in the engineering workshop.
2)Image for a lathe machine :
3)Question Of A Lathe Machine : a)Explain functions of various parts of centre lathe machine . b)Explain with sketch of work piece held to the lathe machine . c)State with sketch the various shapes of tool bits and their function or usage . d)Sketch to explain the various angles of a tool bit tip . e)Explain the materials used in a tool bit . f)Explain the operation of turning boring , facing , drilling , knurkling , tread cutting and off .
4)Answer For Question Of A Lathe Lathe Machine : a)There are 5 main parts of a centre lathe machine : Name of part Track
Equipment forward
Tools back
Quick change gear box
Car
Function -The platform is the backbone of a lathe machine. -The accuracy depends on the rigidity of lathes, alignment, and precision on course. -The top of the track can be V-shaped or flat and on top of other equipment such as tools located forward, cars, and equipment forward. -This section is located to the left of lathe machine. -The main spindle shaped a hollow shaft which is supported by several bearings are located in this section. -At the end of this spindle is some equipment such as choke, live tetengah plate lathe and can be installed and used to hold a workpiece or component to be lathed. -Equipment is located right behind the engine. -It can be moved along the track and can be locked at any desired position. -In the body there is a spindle with a Morse standards. -Site tools with precision machined back to be seated on the right track. -This section is located on the left platform and tools under the front. -It has several different size gears to rotate the shaft of the screw driver or a transmitter. -Screw driver is used to develop the car while w hile cutting threads. -Transmitter shaft was used during a particular transmission rate automatically. -Gap/saddle : *This section is H-shaped bone casting and can be moved on the track. *Apron installed at regular intervals. -Apron : *Parts installed in front apron with a bolt gap.
*Apron is used to control the movement of the gap.
b) There are several methods of holding the work piece using a lathe machine. 1-The method uses the choke hold with four and three-jaw.
2-The method uses the choke hold with collet.
3-The method uses props to hold the fixed and moving props.
c) There are various shapes of tool bits and its functions : 1- Drill twist (TWIST DRILL)
-Shape is similar to a twisted thing. -This spiral of two helical-shaped path through the valley along the drill body. -This drill is used in public works. 2-Combined drill / drill CENTER (COMBINATION & COUNTERSINK / CENTRE DRILL)
-Has two ends and two angles of natural 60 º and 118 º tip. - Used to drill the end of the lathes that can be supported by centre lathe and to make a small hole embedded and can also throw sharp at the end of the drilled hole. -This drill is made in two directions, towards the left and right.
3-AVERAGE END drill
-Form a flat end on this drill is used to smooth the inside of the hole to form a dead end right 90 º. 4-Drill flat (FLAT DRILL)
-Form the end of this drill flat and angled 45 º. Used to pierce large hole in lathe work. 5-Drill a hole embedded (COUNTERSINK DRILL)
-This drill at the end of large and small on the stem. -This drill tip angle of 60 º. -Used to make holes for the sink screw heads unders un ders unders and rivet heads.
6-(COUNTERBORE DRILL)
-This is a two-storey drill diameter. -One for cutting and at the end there is one piece driver to hold the drill string during drilling. -Used to make a hollow floor to sink the head nut or bolt he ad. 7-(STRIGHT DRILL FLUTTED)
-Form of this drill straight groove only. - Used to make a hollow in a soft material such as aluminum and thin materials. 8-(OIL HOLE DRILL)
-Form of this drill with twist drill. -In the body of this drill is the channel; oil directly out to the end, it was to oil can be channeled directly into the surface pores. -This will prevent the heat of the workpiece. -This drill is used in heavy industry.
9-(MULTIPLE FLUTE DRILL)
-This is the same form of drill twist drill twist but deep valley on the body of this drill is more than two. -Used in heavy work. 10-(STEP DRILL)
-Form of this drill twist drill but the same as it has dual diameter. - This drill is used in large works and production.
d)There are various angles of a tool bits :
1-(top rake) : The main function of this angle is in the current scroll production run is made. (This angle is positive or negative slope, see figure). This angle depends on the type of cut material. The rake angle for soft materials such as brass is greater than the material such as mild steel. For machining hard or too soft on the proposed angled rake angle negative.
2-Edge has a rake angle : This angle depends on the material lathed and type of operation performed, eg rough turning, finishing and so on. Large edge angle allows the scroll out easily and reduce friction, but weaken the cutting angle. Rake angle is small and negative sides will strengthen the cutting angle, but this will affect production and will increase the burden of shavings on the tool.
3-ANGLE CUTTERS EDGE This angle is between 10 and 25 and Depending on the application, operation types turning for example polygonal, rough turning and so forth. If the angle of the cutting edge is too large will cause the tool is broken. 4-FRONT END CUTTERS This angle can be changed according to the application. For rough turning angle of 5 to 15 are used. Small angle will strengthen the end of the tool. For ordinary turning angle is between 15 and 30. Large angle of the tool is moved to left shoulder and turning operation to run close to the larva can be done.
e)Materials used in a tool bit , : i)steels : Originally, all tool bits were made of high carbon tool steels with the appropriate hardening and tempering.Since the introductions of high-speed steel (HSS) (early years of the 20th century), sintered carbide (1930s), ceramic and diamond cutters, those materials have gradually replaced the earlier kinds of tool steel in almost all cutting applications. ii) Carbides and ceramics : Carbide, ceramics (such as cubic boron nitride) and diamond, having higher hardness than HSS, all allow faster material removal than HSS in most cases. Because these materials are more expensive and brittler than steel, typically the body of the cutting tool is made of steel, and a small cutting edge made of the harder material is attached. The cutting edge is usually either screwed on (in this case it is called an insert), or brazed on to a steel shank (this is usually only done for carbide).
f)There are operations of turning boring , facing , drilling , knurling , tread cutting and off-centre turning . i)Turning boring
ii)THREAD CUTTING OPERATIONS Before cutting threads, turn down the work piece to the major diameter of the thread to be cut and chamfer the end. Engineering and machinist's handbooks have special tables listing the recommended major and minor diameters for all thread forms. These tables list a minimum and a maximum major diameter for the external threads, and a minimum and maximum minor diameter for internal threads. Lists the most common screw thread sizes. The difference between the maximum and minimum major diameters varies with different sizes of threads. Coarse threads have a larger difference between the two than fine threads. It is common practice, when machining threads on the lathe, to turn the outside
diameter down to the maximum major diameter instead of the minimum major diameter, thus allowing for any error. The work piece may be se t up in a chuck, in a collet, or between centres. If a long thread is to be cut, a steady rest or other support must be used to help decrease the chance of bending the work piece. Lathe speed is set for the recommended threading speed (Machinist Lathe Table 7-2 in Appendix A).To cut threads, move the threading tool bit into contact with the work and zero the compound rest dial. The threading tool bit must be set at the right end of the work; then, move the tool bit in the first depth of cut by using the graduated collar of the compound rest. Position the carriage half nut lever to engage the half nut to the lead screw in order to start the threading operation. The first cut should be a scratch cut of no more than 0.003 inch so the pitch can be checked. Engaging the half nut with the lead screw causes the carriage to move as the lead screw revolves. Cut the thread by making a series of cuts in which the threading tool follows the original groove for each cut. Use the thread chasing dial, Figure 7-82, to determine when to engage the half nut so that the threading tool will track properly. The dial is attached to the carriage and is driven by means of the lead screw. Follow the directions of the thre ad chasing dial, Figure 7-83, to determine when to engage the half nut lever. iii)KNURLING ON THE LATHE Knurling is a process of impressing a diamond shaped or straight line pattern into the surface of a work piece by using specially shaped hardened metal wheels to improve its appearance and to provide a better gripping surface. Straight knurling is often used to increase the work piece diameter when a press fit is required between two part
MILLING MACHINE 1)DEFINITION : A milling machine is a machine tool used to machine solid materials. 2)IMAGE FOR MILLING MACHINE :
3)QUESTION OF MILLING MACHINE THAT GIVEN : a)Differentiate types of milling machines. b)Explain the characteristics and parts of universal milling machine. c)Explain two method of up cut and down cut milling. d)State method of holding cutting tools. e)State methods of holding a work piece. f)State the safety procedures while using the milling machines. g)Name parts of index head.
4)ANSWER FOR QUESTION OF MILLING MACHINE. a)Differences between two types of milling machine. Vertical mill Horizontal mill In the vertical mill the spindle axis is vertically A horizontal mill has the same sort oriented. of x –y table, but the cutters are mounted on a horizontal arbor (see Arbor milling) across the table. There are two subcategories of vertical mills: Plain mills are used to shape flat the bed mill and the turret mill. surfaces. A turret mill has a stationary spindle and the Many horizontal mills also feature table is moved both perpendicular and a built-in rotary table that allows parallel to the spindle axis to accomplish milling at various angles; this cutting. feature is called a universal table. In the bed mill, however, the table moves Some horizontal milling machines only perpendicular to the spindle's axis, while are equipped with a power-takethe spindle itself moves parallel to its own off provision on the table. This axis. allows the table feed to be synchronized to a rotary fixture, enabling the milling of spiral features such as hypoid gears.
2)There are characteristics and parts of universal milling machine .
UNIVERSAL HORIZONTAL MILLING MACHINE The basic difference between a universal horizontal milling machine and a plain horizontal milling machine is the addition of table swivel housing between the table and the saddle of the universal machine. This permits the table to swing up to 45° in either direction for angular and helical milling operations. The universal machine can be fitted with various attachments such as the indexing fixture, rotary table, slotting and rack cutting attachments, and various special fixtures.
c)There are two method of up cut and down cut . Up Cut
Down Cut
•the tool bit workpiece pushing outward from vice •produce a rough surface •workpiece must be firmly secured
•the tool bit workpiece pulling inward from vice •smooth surface •workpiece must be firmly secured
d)Method of holding a work piece.
Many different devices, such as chucks, collets, faceplates, drive plates, mandrels, and lathe centres, are used to hold and drive the work while it is being machined on a lathe. The size and type of work to be machined and the particular operation that needs to be done will determine which work holding device is best for any particular job. Another consideration is how much accuracy is needed for a job, since some work holding devices are more accurate than others. Operational details for some of the more common work holding devices follow. The universal scroll chuck, Figure 7-19, usually has three jaws which move in unison as an adjusting pinion is rotated. The advantage of the universal scroll chuck is its ease of operation in cantering work for concentric turning.
e)Safety procedures while using milling machines Operators of milling machinery should always wear protective gear like ear protectors and safety glasses. Many machine operators are also required to wear steel-toed footwear as a means to prevent any injury in the e vent of heavy metal items dropping onto the floor. Areas around the machine must always be kept clean and free of all metal shavings and debris. Metal debris can be very light in weight an d can be blown away by wind or air. Spread an oil absorbent material around the machine if you spill any cutting lubricant. This will prevent people slipping around the operating area of the machine. Operators must always ensure clothing is buttoned all round and zippers pulled up. Shirt tails must also be tucked in to prevent anyloose clothing getting caught in the rotating machinery. Sometimes this can get the operator pulled into the moving machine. Ensure long hair is tied back in a pony tail and fitted in tight caps. This is because hair can be caught in the rotating spindles of the machine.
f)Name part of index head . i) Types of teeth : The teeth of milling cutters may be made for right-hand or left-hand rotation, and with either right-hand or left-hand helix. Determine the hand of the cutter by looking at the face of the cutter when mounted on the spindle. A right-hand cutter must rotate counter clockwise; a left-hand cutter must rotate clockwise. The right-hand helix is shown by the flutes leading to the right; a left-hand helix is shown by the flutes leading to the left. The direction of the helix does not affect the cutting ability of the cutter, but take care to see that the direction of rotation is correct for the hand of the cutter (Figure 8 -4).
ii) Helical Milling Cutters The helical milling cutter is similar, to the plain milling cutter, but the teeth have a helix angle of 45° to 60°. The steep helix produces a shearing action that results in smooth, vibration-free cuts. They are available for arbour mounting, or with an integral shank with or without a pilot. This type of helical cutter is particularly useful for milling elongated slots and for light cuts on soft metal. See Figure 8-5.
