Limit Fit and Tolerance

1. Interchangeable Manufacture
Definition
The interchangeable manufacture implies that,
the parts that are for practical purposes
identical.They are made to specifications by
processes that ensure that they are so nearly
identical that they will fit into any device of the
same type

2. Examples of Interchangeable
Manufacture
Bottle caps Rims Tires

3. Advantages For Interchangeable
Manufacture
 Replacement: One such part can freely replace
another, without any custom fitting (such
as filling).
 Easy to Assembly: This interchangeability
allows easy assembly of new devices
 Repairing: Easier repair of existing devices.
 Minimizing time and cost :Minimizing both the
time and skill required of the person doing the
assembly or repair.
 Rapid Manufacturing :Machine tool enables the
components to be manufactured more rapidly

4. Size:- It is a number expressed
in a particular unit in the
measurement of length.
Terminology for LIMITS & FITS
 Terminology:- The terms related to limit system are as
below:
Basic Size:- It is the size based
on which the dimensional
deviations are given.
Actual Size:- It is the size of the component by actual
measurement after it is manufactured. It should lie
between the two limits of size.
Hole
Shaft
BasicSize

5.  Limits of size:- These are the maximum and minimum
permissible sizes of the part.
 Maximum limit:- Is the maximum size permitted for the part.
 Minimum limit:- it is the minimum size permitted for the part
limit of size.
 Hole:-Refers to diameter of a circular
hole as well as to any internal dimension
of component .it is referred as “female”
 Shaft:-Limits and fits, all external features of a component
including those which are not cylindrical are designated as
‘Shaft'. It is referred as “male”
Hole
Shaft
Basic
size
Terminology for Limits and Fits Cont.

6. Actual Deviation:- It is the algebraic difference
between actual size and its corresponding basic size.
 Deviation:- It is the algebraic
difference between a size, to its
corresponding basic size. It may be
positive, negative or zero.
Upper Deviation:- It is the
algebraic difference between
maximum limit of size and its
corresponding basic size.
Lower Deviation:- It is the algebraic difference between
minimum limit of size and its corresponding basic size.
Max.dia.
Min.dia.
UpperDeviation
LowerDeviation
Min.dia.
Max.dia.
Shaft
Deviations
Hole

7. Lower limit =  27. 8
 0.2
Upper limit =  28 . 2
Hole
Terminology for Limits and Fits Cont.
Tolerance
zone
Tolerance :Tolerance is the difference between maximum limit of size and
minimum limit of size.
Ø28
(Basic)
Zero line

8. Different Types of Tolerance
 UnilateralTolerance: In this
method of presenting the
limits, both the limits of size
are on the same side of the
zero line.
BilateralTolerance: Here
one of the limits is on one side
of the zero line And the other
limit of size is on the other
side of the line.
Zero line

9. Allowance
 It is an intentional difference between the maximum
material limits of mating parts, For shaft, the
maximum material will be it’s high limit and for
hole, it will it’s low limit
 The positive allowance is clearance and negative
allowance is interference.

10. Fit
 Fit is the relationship that exists between two mating parts, a
hole and shaft with respect to their dimensional difference before
assembly.Three types of fit are given hereunder;
Clearance Fit : In clearance Fit shaft is
always smaller than the hole. A positive
allowance exists between the largest
possible shaft and smallest possible hole.
Minimum Clearance : It is the
difference between the
maximum size of shaft and
minimum size of hole.
Maximum clearance: It is the
difference between the
minimum size of the shaft and
the maximum size of hole
Hole basis
Shaft Basis

11. Fit Cont.
Interference Fit: It is also
called Press or force fit, In
this fit shaft is always
larger than the hole
Minimum interference: it is the
difference between the
maximum size of hole and the
minimum size of shaft prior to
assembly
Minimum Interference: It is the
difference between the
minimum size of the hole and
the maximum size of the
shaft prior to assembly.
Shaft
Hole

12. Fit Cont.
Transition Fit: it is called sliding
Fit . It occurs when the resulting
fit due to the variations in size
of the male and female
components due to their
tolerance, varies between
clearance and interference fits.
The tolerance zones of shaft
and hole overlap
Shaft
Hole

14. Hole Basis System Shaft Basis System
 Hole is keep constant and the shaft
diameter is varied
 The basic size of the hole is taken as
the low limit
 The high limit of the size of the hole
and the two limits of size of the shaft
are selected to give the desired fit
 The actual size of the hole is within
the tolerance limit.
 In this system Hole gets the letter H
and the shaft gets different letter to
decide the position of tolerance
 Shaft is kept constant and the hole diameter
is varied.
 The basic size of the shaft is taken as one of
the limits(maximum) of size of shaft
 The other limit of size of the shaft and the
two limits of hole are then selected to give
the desired fit
 The actual size of a hole that is within the
tolerance limits is always less than the basic
size.
 In this system Shaft gets the letter h and the
hole gets different letter to decide the
position of the tolerance zone to obtain
desired fit

15. Fundamental deviation:-
There are 25 fundamental
deviations in the B.I.S.
system represented by letter,
symbols (Capital letters for
Holes and small letters for
Shaft)
Max.dia.
Min.dia.
UpperDeviation
LowerDeviation
Tolerance
Tolerance
Min.dia.
Max.dia.
Shaft
Hole

17. Grades of Tolerance:- In
the Indian Standard
System, there are 18
grades represented by
number symbols, both for
hole and shaft denoted as
IT01, IT0, IT1,
IT2.....IT16. A high
number
Max.dia.
Min.dia.
UpperDeviation
LowerDeviation
Tolerance
Min.dia.
Max.dia.
Shaft
Hole

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