This document discusses limits, fits, tolerances and surface roughness. It defines standardization and interchangeability, explaining their benefits. It describes limit systems and the terminology used, including types of fits. Clearance, interference and transition fits are defined. Surface roughness is discussed, including how it is measured and expressed. Preferred number series for dimensions are also covered.

1. IMS Engineering College,
Ghaziabad - Delhi NCR
LIMITS,FITS,AND
TOLERANCES AND SURFACE
ROUGHNESS
SUBMITTED TO
Prof. DEEPAK SHARMA
SUBMITTED TO
DIVYANSHU VERMA
ME-1
1214340058

2. Objective
• To inform about standardization
,interchangeability , Terms limits
,fits and tolerances ,surface
roughness and preferred number

3. TOPICS COVERED
1- Standardization
2- Interchangeability
(a)definition
(b) advantages
3- Limits and Fits
(a) Terminology
(b) Types of Fits
(c) Basis of Limit system
(d) Limit gauge
4- Surface roughness
5- Preferred numbers

4. Standardization
The main purpose of standardization is to establish
mandatory or obligatory norms for the design and
production of machines so as to reduce variations
in their types and grades and to achieve quality
characteristics in raw materials, semi-finished and
finished products.
In standardization, the concept of
preferred numbers helps to reduce unnecessary
variations in sizes.
ISO- International Organization of Standard
IS - Indian Standard

5. Benefits of Standardization
• Better product quality
• Mass production of components at low cost.
• Easy availability of parts for replacement and
maintenance
• Less time and effort required to manufacture.
• reduction in variations in size and grades of an
article.

6. Interchangeability
Definition-Situation where two or more
items are so similar in functional and
physical characteristics that they are
considered equivalent in performance and
durability. Each is capable of replacing the
other without causing a need for alteration
or adjustment to fulfill the same
requirement.

7. Examples
Nuts and bolts Rims Tires

8. 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

9. Limits and Fits
LIMITS:‐ These are two extreme permissible
sizes of dimension between which actual dimension is
contained .
FITS:‐It is the relationship existing between mating
parts with respect to amount of play or interference
which is present when they assembled together.
It is the degree of tightness or looseness between two
mating parts to perform definite function

10. Terminology for LIMITS & FITS
1. Basic Size:- It is the size based on which the
dimensional deviations are given.
2. 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.
3. Limits of size:- These are the maximum and minimum
permissible sizes of the part.
4. Maximum limit:- Is the maximum size permitted for the
part.
5. Minimum limit:- it is the minimum size permitted for the
part limit of size.

12. Tolerance- the difference between the upper limit and lower
limit of a dimension is called Tolerance.
When both tolerances on one side ,system is said
to be Unilateral.
when tolerances is allowed on both of nominal
size, said to be Bilateral

13. • 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.
• Actual Deviation:- It is the algebraic difference
between actual size and its corresponding basic size

14. • 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 .

15. Types of fits
• Clearance Fit : In
clearance Fit shaft is
always smaller than the
hole
• Interference Fit: It is also
called Press or force fit, In
this fit shaft is always
larger than the hole

16. Continued..
• 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.

17. Basis of limit system
• Hole basis -Hole is keep constant and the shaft
diameter is varied . The actual size of the hole is
within the tolerance limit
• Shaft basis -Shaft is kept constant and the hole
diameter is varied .

18. Limit gauge
• It inspection tool used to
check a workpiece against its
allowed tolerances.
• A Go-No gauge refers to an
inspection tool used to
check a workpiece against
its allowed tolerances . Its
name derives from its use:
the gauge has two tests;
the check involves the
workpiece having
to pass one test (Go)
and fail the other (No Go).

19. Surface roughness and its
measurement
• Each type of cutting tool leaves its own individual
pattern which therefore can be identified. This
pattern is known as surface finish or surface
roughness.

20. Continued..
• Types of expressing surface roughness
1- Centre line average method (CLA method)
It is defined as the average value of the ordinates
between the surface and mean line , measured on both
side of it .
CLA value or Ra (in microns)=
푦1+푦2+푦3+...푦푛
푛
2- Root mean square method (RMS method)
It is defined as the square root of the arithmetic
mean of the squares of the ordinates.
R.M.S. value(in micron)=
(푦12 + 푦22+. . 푦푛2)/푛

21. Continued…
According to the Indian Standard following symbols
are used to denote the various degree of surface
roughness.
Symbols Surface roughness (Ra) in microns
V 8 to 25
VV 1.6 to 8
VVV .025 to 1.6
VVVV Less than .025

22. Preferred numbers
• In industrial design, preferred numbers (also called
preferred values) are standard guidelines for
choosing exact product dimensions within a given
set of constraints. Product developers must choose
numerous lengths, distances, diameters, volumes,
and other characteristic quantities.
the series of preferred numbers are designated
as R5 ,R20 and R40 respectively.
• R5: 1.00 1.60 2.50 4.00 6.30
• Example - If our design constraints tell us that the
two screws in our gadget should be placed between
32 mm and 55 mm apart, we make it 40 mm,
because 4 is in the R5 series of preferred numbers.

23. Preferred numbers of the basis series
according to ISO3

24. References
• Google.com
• K.M. Moeed
• V. B. Bhandari

25. Thank you