Punyashlok Ahilyadevi Holkar Solapur University, Solapur
S.Y.B. Tech.(Mechanical Engineering) Semester-III
ME214 MACHINE DRAWING & CAD
Teaching Scheme
Lectures – 3 Hours/week
Practical –4 Hour/week
Examination Scheme
ESE– 70 Marks
ISE – 30 Marks
ICA- 50 Marks
POE- 50 Marks
ESE-End Semester Exam
ISE- In Semester Exam.
ICA- Internal Continuous assessment
POE- Practical and Oral Exam
Note: 1.The first angle method of projection should be followed.
2. Practical to be completed using suitable drafting package.
3. The practical examination should be using suitable drafting software
& oral examination will be based on the full syllabus.
University Theory Paper Exam. Scheme :
•Question paper will contain one compulsory question – objective
question for 14 Marks.
•Question paper will contain one compulsory question on Unit No. 4
for 22-24 Marks.
•Question paper will NOT contain any question on Unit No. 5, 6, 7 & 8
Section I
Unit 1– Basics of Machine Drawing & B.I.S. Conventions
Basics of Machine Drawing:-Types of drawing, Dimensioning :Placing of dimensions, Functional and Non- functional dimensions,
Dimensioning common features like: Circular Arcs, Diameters, Holes,
Angles, Chamfers, Tapers, Undercut, Repetitive features,
Countersunk, Square, Sphere, Across flat, Threads, etc.
Types of drawing :1.
2.
3.
4.
Machine Drawing
Production Drawing
Part Drawing
Assembly Drawing
Placing of dimensions :Aligned Dimensioning System
Unidirectional Dimensioning System
Functional and Non- functional dimensions :-
Dimensioning common features like: Circular Arcs, Diameters, Holes, Angles,
Chamfers, Tapers, Undercut, Repetitive features, Countersunk, Square, Sphere,
Across flat, Threads, etc.
Arrangement of Dimensions
Types of Section
Study of B.I.S. (Bureau of Indian Standards) ConventionsSignificance and importance of BIS Conventions, Drawings sheet sizes
and layout recommended by BIS. Conventional representation of
engineering Materials, spur helical and bevel gears, worm and worm
wheel, rack and pinion, gear assemblies, type of helical, disc and leaf
springs. Internal and external threads, square head, spline shaft,
diamond knurling BIS conventions for sectioning, type of sections,
exceptional cases. BIS methods of linear- and angular dimensioning.
Symbolic representation of welds as per BIS. Surface finish symbol
Gear Assembly
Unit 2– Free Hand Sketching of machine component
Importance of sketching and entering proportionate
dimensions on sketches. Free hand sketches of various
types of threads, nut, bolts (square and hexagonal flanged
nuts, lock nuts, dome nut, capstan nut, wing nut, castle nut,
split pin, square headed bolt, cup headed bolt, T-headed
bolt, Rag foundation bolt, stud, washer. Various types of
rivets and riveted joints, Various types of keys, Socket and
spigot (Cotter joint) , Knuckle (pin) joint, Muff coupling,
Protected and unprotected Flanged, coupling, universal
coupling, solid and bush bearing. Plummer block (pedestal
bearing), foot step bearing. Flat and V-belt pulleys, Fast
and loose pulleys, speed cone pulleys, Pipe joint for C.I.
Flanged, socket and spigot type pipe joint. Union pipe joint
and standard pipe-fitting. The applications of above
machine components.
Types of Threads
Types of Nut
Hexagonal and Square Nut
Locking with Split Pin
Types of Bolt
Castle Nut
Rag Foundation Bolt
Stud
Single Riveted Lap Joint
Single Riveted Single Strap Butt Joint
Single Riveted Double Strap Butt Joint
Peg Feather key
Single Head Feather key
Double Head
Feather key
Cotter joint with socket and spigot ends
Knuckle joint
Muff Coupling
Unit 3– Production Drawing: Limits, Fits, & Tolerances
•Dimensional Tolerances: Introduction to system of limits and fits. Basic
concepts. Terminology, Tolerances, various types. Necessity of Limit system,
Unilateral and Bilateral Tolerances, Relation between Tolerances and
Manufacturing Processes, Methods of indicating tolerances on drawings, IT grades,
Types of fits, Grades of tolerances, types of Holes & shafts based on fundamental
deviations, designation of fit, Systems of fits, Selection of fits, Selection of
tolerances based on fits
•Geometrical Tolerances:- Need of Geometrical Tolerances, Terminology,
Tolerances for
Single Features such as Straightness, Flatness, Circularity, Cylindricity. Tolerances
for Related Features such as Parallelism, Perpendicularity, Angularity,
Concentricity, Tolerance Symbol and Value, Indicating Geometrical Tolerances on
drawings.
•Surface Finish:- Surface Texture, Surface Roughness Number, Roughness
Symbols, Range
of Roughness obtainable with different manufacturing processes.
(Note : Numerals /calculations/problems/tasks/examples/theoretical
questions on UNIT NO.3)
Tolerance:The permissible variation of a size is called tolerance. It is the
difference between the maximum and minimum permissible limits
of the given size. If the variation is provided on one side of the basic
size, it is termed as unilateral tolerance. Similarly, if the variation is
provided on both sides of the basic size, it is known as bilateral
tolerance.
Limits:The two extreme permissible sizes between which the actual size is
contained are called limits. The maximum size is called the upper
limit and the minimum size is called the lower limit.
Deviation:It is the algebraic difference between a size (actual, maximum, etc.)
and the corresponding basic size.
Upper Deviation:It is the algebraic difference between the maximum limit of the size
and the corresponding basic size.
Lower Deviation:- It is the algebraic difference between
the minimum limit of the size and the corresponding basic
size.
Allowance:- 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 interference.
Basic Size:-It is determined solely from design
calculations. If the strength and stiffness requirements
need a 50mm diameter shaft, then 50mm is the basic shaft
size. If it has to fit into a hole, then 50 mm is the basic size
of the hole
If the difference between the hole and shaft sizes is negative
before assembly; an interference fit is obtained.
Hole Basis System:- In this system, the size of the shaft is
obtained by subtracting the allowance from the basic size
of the hole. This gives the design size of the shaft.
Tolerances are then applied to each part separately. In this
system, the lower deviation of the hole is zero. The letter
symbol for this situation is ‘H’.
The hole basis system is preferred in most cases,
since standard tools like drills, reamers, broaches, etc., are
used for making a hole.
Shaft Basis System:- In this system, the size of the hole is
obtained by adding the allowance to the basic size of the
shaft. This gives the design size for the hole. Tolerances are
then applied to each part. In this system, the upper
deviation of the shaft is zero. The letter symbol for this
situation is ‘h’.
To obtain different types of fits, it is general practice to vary
tolerance zone of one of the mating parts
HOLE BASED SYSTEMSize of hole is kept constant,
shaft size is varied
to get different fits.
SHAFT BASED SYSTEMSize of shaft is kept constant,
hole size is varied
to get different fits.
How to interpret fit
100 H7 n6
100
Basic
Size
Which
table to
see
H
Fundamental
deviation for
HOLE
7
n
IT Grade for
HOLE
Fundament
al deviation
for SHAFT
Fundamental Fundamental
Deviation
tolerance
table for
table for
Holes
Holes
6
IT Grade for
SHAFT
Fundamental Fundamental
Deviation
tolerance
table for
table for
Shafts
Shafts
Methods of Placing Limit Dimensions
Method-1
Where:- H=Basic Hole (Lower Devastation is Zero)
7= Grade (Value available in chart)
h= Basic Shaft (Upper Devastation is Zero)
Method-2
Method-2
Lower Deviation
Upper Deviation
Lower Deviation
Upper Deviation
• C) Identify the type of fit indicate with following fit
designation.
• a) 150 H7 f7
• b) 100 H9 p6
• c) 65 H7 r6
• Also to support the answer, write/draw-the
calculations/explanation/diagram for the same.
ф150 H7 f7
Hole:- ф150H7 = +0.040 (From Chart)
+0.000
Upper Limit for Hole = ф150.040mm
Lower Limit for Hole = ф150.00mm
Shaft:- ф150f7 = -0.043 (From Chart)
-0.083
Upper Limit for Shaft = ф149.957mm
Lower Limit for Shaft = ф149.917mm
UL
Basic
LL
Hole
ф150.040
ф150.000
ф150.00
Size
UL
ф 149.957
LL
ф 149.917
Shaft
Hence Fit is Clearance Fit
Calculate the working dimensions, recognize the type
of fit and calculate the maximum clearance/interference
for 100 H7n6 combination. Represent the limit sizes by
drawing proportionate fig.
Geometric Tolerances
Geometric shape of a component is considered exact unless specified.
e. g.
Straight line means straightness
Circle means that the profile is exactly circular
Parallel line means that these are exactly parallel
Lines at right angles to each other implies perpendicularity.
These form variations are called as geometric tolerances and these
also have to be within limits. And less than the Dimensional
tolerances.
Types of tolerances
Terminology
• Geometric Tolerance: It is the maximum
permissible variation of form, orientation,
location and run out specified on a production
drawing.
• Tolerance Zone: It is an imaginary zone within
which a component must be contained.
• Feature : It is specified portion of a
component such as hole, slot surface or
profile.
• Axis : Axis is the theoretical straight line
about which a circular feature revolves.
• Median : It is the center line of a straight
or a bent shaft.
Frame
• Frame is a box having some partitions.
• Datum : It is a theoretical point, lines or a plane from
which dimensions are measured and geometric
tolerances are referenced.
• 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
• Datum triangle : Datum is shown by a triangle (open
or filled) on the datum feature.
• Datum letter : It is an upper case letter enclosed in a
box to indicate an arbitrary name of a datum.
Tolerance
Symbols
Tolerance
Symbols
Form tolerance for single
features
• Straightness : Straightness of a line/axis
or of a line on a surface is the
perpendicular distance between two
parallel lines touching the crest and the
valleys of the line/surface.
Straightness example
• Flatness : Flatness is the distance between
two imaginary planes enclosing the actual
surface at the lowermost and uppermost
positions.
• Circularity (Roundness): Tolerance value of
circularity is the difference maximum and
minimum radii of a cylinder any section.
• Cylindricity : Cylindricity is the difference in
value of radii between two imaginary
cylinders, enveloping cylinders at outermost
and innermost surfaces.
• Profile of a line : The variation lies between
the two curves which envelop the actual
curve.
• Profile of a Surface : Tolerance zone for a
profile of a surface is the space between two
surfaces of same profile which envelopes the
highest and the lowest point of the surface
keeping the same profile.
Tolerance on related features
• Parallelism : Tolerance on parallelism is the zone
between two parallel surfaces enveloping the
feature in relation to the datum surface.
• Perpendicularity : Perpendicularity tolerance is
the zone between two perpendicular planes to
the datum within which the controlled feature
should lie.
• Also called as tolerance on squareness.
• Angularity : Tolerance on angularity is the zone
between two parallel planes inclined to the
datum plane at the specified angle in which the
controlled feature lies.
• Angularity is not defined in terms of angles.
• Concentricity : Tolerance on concentricity is the
diameter of a circular zone within which the axes
of the two cylindrical features may offset from
each other.
• Symmetry : Symmetry means the position of a
feature is symmetric in relation to datum.
• Position : The actual centre of the circle may lie
within a tolerance zone indicated by a small
circle of diameter 0.1 mm.
Run out
• Circular Run out : Circular run out is the
deviation from an ideal surface when a part is
rotated by 3600. It could be radial or axial both.
• Total Run out : Total run out is not a circular run out at one
particular position but found when the dial indicator is
moved axially over the entire surface parallel to the axis of
datum while the part is being turned.
• The difference between the minimum and maximum dial
indicator reading from the beginning to the end while
rotating the surface is the total run out.
Surface Roughness
• Roughness is the fine irregularity in the surface.
Caused by cutting edge tool in case of machined
surface.
Profiles
Roughness Symbol
a: Ra Value in micrometre or Roughness grade number
b: Production Method, treatment or coating
c: Sampling Length
d: Direction of lay
e: Machining Allowance
f: Other roughness values (In Bracket)
Machining symbols
a) The basic symbol
b) If the removal of material is not permitted, a circle is added to the basic
symbol
c) If the removal of material by machining is required, a bar is added to the
basic symbol
d) When special surface characteristics have to be indicated, a line is added
to the longer arm of the basic symbol
Indication of surface
roughness
A surface texture specified above
a. may be obtained by any production method.
b. must be obtained by removal of material by machining.
c. must be obtained without removal of material.
a.
If it is necessary to impose maximum and minimum limits of surface
roughness, both the values should be shown, with the maximum limit, a1,
above the minimum limit, a2
b.
If it is required that the final surface texture be produced by one particular
production method, this method should be indicated on an extension of the
longer arm of the symbol
c.
If it is necessary to define surface texture, both before and after treatment,
this should be explained by a suitable note or as shown in Fig.
d.
Sampling length
e.
If it is necessary to control the direction of lay, it is specified by a symbol
added to the surface roughness symbol, as shown in Fig.
The direction of lay is the direction of the predominant surface pattern,
ordinarily
determined by the production method employed.
Symbols Representing Direction
of Lay
Symbols Representing Direction
of Lay
Equivalent Surface roughness symbol
Roughness Symbol and their
meaning
Examples
6.3
0.8
0.8
All over
0.03
0.01
A
A
Examples
Example
Example
Example