JNTUH SYLLABUS: (A70391) PRODUCTION DRAWING PRACTICE UNIT — I CONVENTIONAL REPRESENTATION OF ATERIALS: conventional representation of parts —
screw joints, joints, welded joints, joints, springs, springs, gears, electrical, electrical, hydraulic hydraulic and pneumatic pneumatic circuits circuits — methods of indicating notes on drawings. L!"!#$ L!"!#$%% F!#$ F!#$ &' T*+,&'*+,&'-+$: +$: Types Types of fits. fits. exerci exercises ses involvin involving g select selectio ion n / interpre interpretati tation on of fits fits and
estimation of limits from tables. UNIT — II
Introdu oduct ctio ion n and indic indicati ation on of form form and and posit positio ion n FOR FOR AND POSIT POSITION IONAL AL TO TOLE LERA RANCE NCES: S: Intr tolerances on drawings, types of run out, total run out and their indication. UNIT — III SURFACE ROUGHNESS AND ITS INDICATION: Defi Defini niti tion on,, types types of of surf surfac acee rou r oughn ghn ess ind ica tio n —
urf ace roug hnes s obta inab le from var ious manufa manufactu cturin ring g process processes. es. recom recommen mended ded surfa surface ce roughne roughness ss on mecha mechanic nical al components. !eat treatment an d surface treatment s ymbols used on drawin drawings. gs. UNIT — IV
with indications indications of DETAILED DETAILED AND PART DRAWINGS: DRAWINGS: Drawing of parts from assembly drawings with si"e, tolerances, roughness, form and position errors etc. UNIT — V PRODUCTION DRAWING PRACTICE: #art drawing drawingss using using computer computer aided aided drafting draftin g by b y $%D $% D softwar so ftwaree
TE.T BOO/S:
&.#roduction and Drawing /' .(. )arayana * #. 'annaiah/ )ew %ge +.achine Drawing with %uto $%D/ #ohit and -hosh, #
REFERENCES:
&.-eometric dimensioning dimensioning and tolerancing/ames tolerancing/ames D. eadows/ 0. #ub lications licatio ns +.ngineering etrology/ 1.'. ain/'hanna #ublications
UNIT I Representation of Materials & Machine Components
UNIT –II LIMITS and FITS
LIIT SYSTE: 2ollowing are some of the terms used in the limit system, T*+,&'-+: T*+,&'-+: The permissible variation of a si"e is called tolerance. It is the difference between the
maximum and minimum permissible minimum permissible limits limits of the given si"e. L!"!#$: The two extreme permissible si"es between which the actual si"e is contained are called limits.
The maximum si"e is called the upper limit and the minimum si"e is c alled the lower limit. D+!&#!': It is the algebraic difference between a si"e 3actual, max imum, etc.4 and the corresponding basic
si"e. A-#&* D+!&#!': It is the algebraic difference between the actual si"e an d the corresponding basic si"e.
the algeb algebra raic ic diff differ eren ence ce betwe between en the the maxi maximu mum m limi limitt of the the si"e si"e and and the the U22+, U22+, D+!&# D+!&#!' !':: It is the corresponding basic si"e. the algeb algebra raic ic diff differ eren ence ce betw between een the the mini minimu mum m limi limitt of the the si"e si"e and the the L+, L+, D+!&# D+!&#!' !':: It is the corresponding basic si"e. A**&' A**&'-+: -+: It is the dimensional difference between the maximum material limits of the mating parts,
intentionally provided to obtain the desired class of fit. If the allowance is positive, it will result in minimum clearance between the mating parts and if the allowance is negative, it will result in maximum maximum interference.
FITS:
The relation between two mating parts is 5nown as a fit. Depending upon the actual limits of the hole or shaft si"es, fits may be classified as clearance fit, transition fit and interference fit. C*+&,&'-+ F!#: It is a fit that gives a clearance between the two mating parts.
T,&'$!#!' F!#: This fit may result in either interference or a clearance, depending upon the actual values
of the tolerance of individual parts.
I'#+,4+,+'-+ F!#: If the difference between the hole and shaft si"es is negative before assembly6
an interference fit is obtained.
HOLE BASIS SYSTE% SHAFT BASIS SYSTE
In wor5ing out limit dimensions for the three classes of fits6 two systems are in use,
viz. ,
the hole basis
system and shaft basis system HOLE BASIS SYSTE : In this system, the si"e of the shaft is obtained by subtracting the allowance
from the basic si"e of the hole. In this system, the lower deviation of the hole is "ero. The letter symbol for this situation is 7 H 8. 8. SHAFT BASIS SYSTE : In this system, the si"e of the hole is obtained by adding the allowance to
the basic si"e of the haft. Tolerances Tolerances are then applied to each part. In this system, the upper deviation of the shaft is "ero. The letter symbol for this situation is 7h8.
Datum feature:
A datum feature is a feature of a part, such as an edge,
surface, or a hole, which forms the basis for a datum or is used to establish its location.
UNIT III FORM AND POSITIONA TO!RANC!S
Surface Rou"hness an# its In#ication & $eat an# Surface Treatment S%mols Surface Rou"hness: The properties and performance of machine components are affected by the degree of roughness of the various surfaces. The higher the smoothness of the surface, the better is the fatigue fatigue strength and corrosion resistance. 2riction 2riction between mating parts is also reduced due to better surface finish.
Surface Rou"hness Numer: The surface roughness number represents the average departure of the surface from perfection over a prescribed prescribed sampling length and and is expressed in microns.
The surface roughness may be measured, using any one of the following9 &. traight edge +. urface gauge :. ;ptical flat <. Tool Tool ma5er8s microscope =. #rofilometer #rofilometer >. #rofilograph #rofilograp h ?. Talysurf Talysurf
Machine S%mols: The basic symbol consists of two legs of une@ual length, inclined at approximately >AB to the line, representing the surface considered. This symbol may be used where it is necessary to indicate that the surface is machined, without indicating indicating the grade of roughness or the process to be used.
( a ). Basic Symbol ( b ). Material Removal Removal is not allowed Removal Removal of Material is allowed ( d ). Special Surface haracteristics
( c ).
In#ication of Machinin" Allo'ancce:
In#ication of Special Rou"hness Characteristics:
!n certain circumstances, for functional reasons, it may be necessary to specify additional special re"uirements, concerning surface roughness. !f it is re"uired that the #nal surface te$ture be produced by one particular production method, this method should be indicated on an e$tension of the longer arm of the symbol. Also, any indications indication s relating to treatment of coating may be given on the e$tension of the longer arm of the symbol.
UNIT IV 5 V D!TAI!D an# PART DRA(IN)S S#44!'6 B is used to prevent loss of fluid such as steam, between sliding or turning parts of machine
elements. In a steam engine, when the piston rod reciprocates through the cylinder cover6 stuffing box provided in the cylinder cover, prevents lea5age of steam from the cylinder. cylinder.
C,$$8+& C,$$8+& is used in hori"ontal steam engines for connecting the piston rod and connecting rod. The -,$$8+& , with the help of slide bloc5 <, reciprocates between two guides provided in the engine frame.
The gudgeon pin :, connects the slide bloc5s with the crosshead bloc5 &. This acts as a pin joint for the connecting rod 3not shown in figure4. The piston rod + is secured to the -,$$8+& bloc5 by means of the cotter cotter =. The assembly assembly ensure ensuress recipr reciprocat ocating ing motion motion along along a straig straight ht line line for the piston piston rod and reciprocating cum oscillatory motion for the connecting rod.
E--+'#,!- is used to provide a short reciprocating motion, actuated by the rotation of a shaft. E--+'#,!-$ are used for operating steam valves, small pump plung ers, sha5ing screens, etc. 1otary motion can be converted into a reciprocating motion with an eccentric, but the reverse conversion is not no t possible due to excessive friction between the sheave and the strap. The sheave + which is in the form of a circular disc with a stepped rim is 5eyed on the shaft. Chen the shaft rotates, the sheave rotates eccentrically because of the eccentrically placed hole in it and imparts reciprocating motion to eccentric rod >. The straps & are semicircular elements with an annular recess to accommodate the stepped rim of the sheave. These are held together on the sheave by means of strap bolts <, with pac5ing pac5 ing strips : placed between them. The eccentric rod is fixed to the eccentric eccen tric strap by means of the studs and nuts n uts =.
C''+-#!'6 , is used in center cran5 engines. The bearing bush < which is in one piece, is fitted at the
small end of the connecting rod &. The small end of the rod is connected to the piston. The main bearing bush, which is split into two halves, is placed at the big end en d of the connecting conn ecting rod. The big end of the rod is connected to the cran5 pin of the center cran5. 2irst, the split bearing brasses : are placed on the cran5 pin, then the big end of the connecting connec ting rod and the cap + are clamped onto these, by means of two bolts = and nuts >.
S-,+ &- s are used for raising heavy loads through very small heights. In this, the screw : wor5s in the
nut + which is press fitted into the main body &. The tommy bar ? is inserted into a hole through the enlarged head of the screw and when this is turned, the screw will move up or down, thereby raising or lowering the load.
P!2+ P!2+ !-+$ !-+$ are designed for holding pipes, to facilitate operations such as threading or cuttingoff to
re@uired re@uired length. To assemble assemble the vice, the screw rod < is screwed into the base & from above. Chen the circular groove at the end of the screw rod is inline with the > mm diameter transverse hole in the housing, the movable jaw + is inserted from below. %fter alignment, two set screws : are inserted into the jaw. This This arrangement allows the jaw to move vertically without rotation when wh en the handle is operated and the screw is turning. The Eshaped base of the housing can accommodate pipes of different diameters. The serrations provided on the Eshaped end of the movable jaw provide effective grip on the pipe surface.
P*""+, ;*- is used for long shafts, re@uiring intermediate support, especially when the shaft cannot be introduced into the bearing, endwise. The bottom half + of the bearing brass is placed in the base & such that, the snug of the bearing enters into the corresponding recess in the base6 p reventing rotation of the brasses. %fter %fter placing the journal 3shaft4 on the bottom half of the bearing brass, 5ept in the base6 the upper half of the bearing brass : is placed and the cap < is then fixed to the base, by means of two bolts with nuts =. The bearing is made of two halves h alves so that the support can be introduced at any location of the long shaft.
U'!+,$ U'!+,$&* &* -2*!' -2*!'6 6 is a rigid coupling and is used to connect two shafts, whose axes intersect if
extended. The for5s + are mounted at the ends of two shafts &, ma5ing use of sun5 5eys >. The central bloc5 :, having two arms at right angle to each other, is placed between the for5s and connected to both of them by using pins < and collars =. % taper pin 3not shown4 is used to 5eep the pins < in position. During rotation of shafts, the angle between them can be varied.
