2. 2
Different types of tolerances are
1. Dimensional Tolerances
2. Form Tolerances
3. Position Tolerances
4. Surface Roughness values
5. Combination Tolerances
Other details shown on drawing are
Material specification
Special treatments if any
Heat treatments
Assembly condition
Special notes
3. 3
Tolerance: Tolerance is the total permissible variation
from the specified basic size of the part. It is defined as
the magnitude of permissible variation of a dimension or
measured control criterion from specified value.
Basic size: The basic size is the size on which variation
permitted.
Actual size:
The size of a feature obtained by measurement
4. 4
TOL not specified
• Follow general engineering tolerance
• IS 2102 fine, medium, course & very
course
• Unless otherwise specified, it is medium.
• Or else it can be IT 14 VALUE, bilateral
• All drawings need contain conditions on
general tolerance.
5. 5
1. Open tolerances or General Engineering tolerances
Standards used are
IS 2102 ( Part – 1) – 1993 / ISO 2768 - 1 : 1989
General Tolerances
Part – 1: Tolerances for Linear and Angular
dimensions without individual tolerance indications
Part – 2: Geometrical Tolerances for features without
individual tolerance indications
Ex: 20.0, 20-f, Ø20-f H
6. 6
Table 1 – Permissible deviations for linear dimensions except for broken edges
(external radii and chamfer heights, see table 2)
Values in millimeters
Tolerance Class
Permissible deviations for basic size range
Desig
nation
Descripti
on
0.5
up to
3
Over
3
up to
6
Over
6
up to
30
Over
30
up to
120
Over
120
up to
400
Over
400
up to
1000
Over
1000
up to
2000
Over
2000
up to
4000
f fine ± 0,05 ± 0,05 ± 0,1 ± 0,15 ± 0,2 ± 0,3 ± 0,5 -
m medium ±
0,1
± 0,1 ± 0,2 ± 0,3 ± 0,5 ± 0,8 ± 1,2 ± 2
c coarse ±
0,2
± 0,3 ± 0,5 ± 0,8 ± 1,2 ± 2 ± 3 ± 4
v very
coarse
- ± 0,5 ± 1 ± 1,5 ± 2,5 ± 4 ± 6 ± 8
1) For nominal sizes below 0,5 mm, the deviations shall be indicated adjacent to the
relevant nominal size (s).
7. 7
Table 2 – Permissible deviations for broken edges
( external radii and chamfer heights)
Values in millimeters
Tolerance Class
Permissible deviations for basic
size range
Designation Descriptio
n
0.5 up to 3 Over 3 up
to6
over 6
f fine
± 0,2 ± 0,5 ± 1
m medium
c coarse
± 0,4 ± 0,1 ± 2
v very
coarse
1) For nominal sizes below 0.5 mm, the deviations shall be
indicated adjacent to the relevant nominal size(s).
8. 8
Table 3 – Permissible deviations of angular dimensions
Tolerance Class
Permissible deviations for ranges of lengths, in
millimeters,
of the shorter side of the angle concerned
Desig
nation
Descript
ion
up to 10 over 10
up to 50
over 50 up
to 120
over 120
up to 400
over
400
F fine ± 10 ± 00 30 ± 00 20’ ± 00 10’ ± 00 5
m medium
c coarse ± 10 30’ ± 10 ± 00 30’ ± 00 15’ ± 00
10
v very
coarse
± 30 ± 20 ± 10 ± 00 30’ ± 00 20
9. 9
Table 1 – General tolerances on straightness and flatness
Values in millimeters
Tolerance
Class
Straightness and flatness tolerances for ranges of nominal lengths
up to 10
over 10 up
to 30
over 30 up
to 100
over 100
up to 300
over 300 up to
1000
Over 1000
up to 3000
H 0,02 0,05 0,1 0,2 0,3 0,4
K 0,05 0,1 0,2 0,4 0,6 0,8
L 0,1 0,2 0,4 0,8 1,2 1,6
10. 10
Table-2 General tolerances on perpendicularity
Values in millimeters
Tolerance
Class
Perpendicularity tolerances for ranges of nominal
lengths of the shorter side
up to 100
over 100
up to 300
over 300
up to 1000
over 1000
up to 3000
H 0,2 0,3 0,4 0,5
K 0,4 0,6 0,8 1
L 0,6 1 1,5 2
11. 11
Table-3 – General tolerances on symmetry
Values in millimeters
Tolerance
Class
Symmetry tolerances for ranges of
nominal lengths
up to 100
over 100
up to 300
over 300
up to 1000
over 1000
up to 3000
H 0,5
K 0,6 0,8 1
L 0,6 1 1,5 2
12. 12
Table 4 – General tolerances on circular run-out
Values in mm
Tolerance class Circular run-out tolerances
H 0,1
K 0,2
L 0,5
13. 13
IS 2102 – PART – 2
• VALUES FOR – Straightness /
perpendicularity / symmetry / Run out
specified
• Circularity - limited to diameter
tolerance or run out value
• Cylindricity – Limited to combined effect
of CIRCULARITY& PARALLELISM.
• Parallelism – Limited to Dimensional
Tolerance & flatness tolerance.
• Coaxiality - Limited to run out tolerance.
14. 14
ISO 2768 - m
• General Engg. Tole Tolerance class medium
IS 2102 – f
• General Engg. Tole – class fine
15. 15
ISO 2768 – mK
• General Engg. Tole for dimensions -
Tolerance class. m
• General Engg. Tole for form / position –
tolerance class. K
16. 16
ISO 2768 - K
• General tol. as dim not considered.
• Form/position as per tol. Class K.
18. 18
2. Specificied tolerances
Standards used
IS 919 (Part – 1) – 1993 / ISO 286 – 1 : 1988
ISO System of Limits and Fits
Part – 1: Bases of tolerances, Deviations and Fits
Part – 2: Tables of standard tolerance Grades and
limit Deviations for Holes and shaft.
Example : 20H7, 20g6, 30 + 0.02
Specific tolerance should be less than open tolerance
20. 20
HOW MUCH IS THE VALUE
• IS 919 / SP46 OR STD CHARTS SPECIFY.
• 18 GRADES ARE SPECIFIED. VALUE IS
ATTACHED TO A GRADE
• IT=INTERNATIONALTOLERANCE
GRADE.
• AND 18 REPRESENT THE ROUGHFEST
Mfg process
• EVERY MANUFACTURING PROCESS IS
ATTRIBUTED WITH A RANGE OF
ACCURACY GRADE
21. 21
HOW MUCH IS THE VALUE
FOR EX;
• TURNING IT7, 8 OR 9
• GRINDING IT 5, OR 7
• MILLING IT 6, 7, OR 8
• LAPPING IT 1, 2, 3, OR 4
• SAND CASTING IT 16, 17, 18
• PRESS WORKING IT 10, 11 OR 12
• INJ. MOULDING IT 12. 123 OR 14
22. 22
Grades of tolerances obtainable by various
manufacturing processes
According to IS 18 grades of tolerances or accuracy
grades of manufacturing IT1, IT2, IT3….IT18
IT GRADE is generally indicated by numbers from
1 to 18
26. 26
HOW MUCH IS THE VALUE.
• EVERY DIM. ALONG WITH A GRADE
RECEIVE A TOL. VALUE.
• FOR EX. DIM 40 & GRADE 8, TOL= ?
• STD. FORMULA APPLIES TO THIS VALUE
• FOR CONVENIENCE, DIMES. ARE
GROUPED. 0 TO 3; 3 TO 6; 6 TO 10 etc.
• SAME VALUE OF TOL. VALID FOR A DIA
GROUP WITH ONE GRADE.
28. 28
Table 1 – Numerical values of standard tolerance grades IT for basic sizes up to 3 150 mm
Standard tolerance grades
Basic size
mm IT12)
IT22)
IT32)
IT42)
IT52)
IT6 IT7 IT8 IT9 IT10 IT11
Above
Up to
and
including
Tolerances
m
- 33
0,8 1,2 2 3 4 6 10 14 25 40 60
3 6 1 1,5 2,5 4 5 8 12 18 30 48 75
6 10 1 1,5 2,5 4 6 9 15 22 36 58 90
10 18 1,2 2 3 5 8 11 18 27 43 70 110
18 30 1,5 2,5 4 6 9 13 21 33 52 84 130
30 50 1,5 2,5 4 7 11 16 25 39 62 100 160
50 80 2 3 5 8 13 19 30 46 74 120 190
80 120 2,5 4 6 10 15 22 35 54 87 140 220
120 180 3,5 5 8 12 18 25 40 63 100 160 250
180 250 4,5 7 10 14 20 29 46 72 115 185 290
250 315 6 8 12 16 23 32 52 81 130 210 320
315 400 7 9 13 18 25 36 57 89 140 230 360
400 500 8 10 15 20 27 40 63 97 155 250 400
500 6302
9 11 16 22 32 44 70 110 175 180 440
630 8002
10 13 18 25 36 50 80 125 200 320 500
800 10002
11 15 21 28 40 56 90 140 230 360 560
1000 12502
13 18 24 33 47 66 105 165 260 420 660
1250 16002
15 21 29 39 55 78 125 195 310 500 780
1600 20002
18 25 35 46 65 92 150 230 370 600 920
2000 25002
22 30 41 55 78 110 175 280 440 700 1100
2500 31502
26 36 50 68 96 135 210 330 540 860 1350
1) Values for standard tolerance grades IT01 and IT0 for basic sizes less than or equal to 500 mm are given in ISO 286 – 1, annex A, table 5.
2) Values for standard tolerance grades IT1 to IT5 (incl.) for basic sizes over 500 mm are included for experimental use.
3) Standard tolerance grades IT14 to IT18 (incl.) shall not be used for basic sizes less than or equal to 1 mm.
29. 29
Table 1 – Numerical values of standard tolerance grades IT for basic sizes up to 3 150 mm
Standard tolerance grades
Basic size
mm IT12 IT13 IT143)
IT153)
IT163)
IT173)
IT183)
Above
Up to and
including
Tolerances
mm
- 33
0,1 0,14 0,25 0,4 0,6 1 1,4
3 6 0,12 0,18 0,3 0,48 0,75 1,2 1,8
6 10 0,15 0,22 0,36 0,58 0,9 1,5 2,2
10 18 0,18 0,27 0,43 0,7 1,1 1,8 2,7
18 30 0,21 0,33 0,52 0,84 1,3 2,1 3,3
30 50 0,25 0,39 0,62 1 1,6 2,5 3,9
50 80 0,3 0,46 0,74 1,2 1,9 3 4,6
80 120 0,35 0,54 0,87 1,4 2,2 3,5 5,4
120 180 0,4 0,63 1 1,6 2,5 4 6,3
180 250 0,46 0,72 1,15 1,85 2,9 4,6 7,2
250 315 0,52 0,81 1,3 2,1 3,2 5,2 8,1
315 400 0,57 0,89 1,4 2,3 3,6 5,7 8,9
400 500 0,63 0,97 1,55 2,5 4 6,3 9,7
500 6302
0,7 1,1 1,75 2,8 4,4 7 11
630 8002
0,8 1,25 2 3,2 5 8 12,5
800 10002
0,9 1,4 2,3 3,6 5,6 9 14
1000 12502
1,05 1,65 2,6 4,2 6,6 10,5 16,5
1250 16002
1,25 1,95 3,1 5 7,8 12,5 19,5
1600 20002
1,5 2,3 3,7 6 9,2 15 23
2000 25002
1,75 2,8 4,4 7 11 17,5 28
2500 31502
2,1 3,3 5,4 8,6 13,5 21 33
1) Values for standard tolerance grades IT01 and IT0 for basic sizes less than or equal to 500 mm are given in ISO 286 – 1, annex A, table 5.
2) Values for standard tolerance grades IT1 to IT5 (incl.) for basic sizes over 500 mm are included for experimental use.
3) Standard tolerance grades IT14 to IT18 (incl.) shall not be used for basic sizes less than or equal to 1 mm.
30. 30
HOW MUCH IS THE VALUE
• 60% INCREASE IN TOL. VALUE FOR
EVERY GRADE UP FOR A DIA
GROUP
• EVERY 6TH GRADE GETS 100%
MORE TOL VALUE
31. 31
WHERE TO DISPOSE TOLE.
• TOL. CAN BE DISPOSED
• ABOVE BASIC DIM.
• BELOW BASIC DIM
• DISTRIBUTED ON EITHER SIDE
32. 32
WHERE TO POSITION
• POSITIONING IS REPRESENTED BY
CAPITAL LETTERS FOR HOLES A,B,H
• BY SMALL LETTERS FOR SHAFTS a,b,h
• STD DISTANCES ARE KEPT EACH
LETTER & FOR EACH DIA GROUP FROM
BASIC DIM.
• THE DISTANCE TO THE BASIC DIM WITH
LEAST VALUE IS TERMED AS
FUNDEMENTAL DEVIASION;
• FD IS FIXED FOR A DIA-DIM
COMBINATION.
37. 37
FITS
When two parts to be assembled, the relation
resulting from the difference between the size
before assembly is called a fit.
A fit is represented by
30 H 7 / g6, 30 H 7 / p6, 40 H7/h6,
40 H7k6, 40 H7p6,
46. 46
MMC, LMC & RFS
MMC - Dimension corresponding to Maximum
Metal Condition
(biggest shaft size or smallest hole size)
LMC - Dimension corresponding to Least Metal
Condition
(smallest shaft or biggest hole size)
RFS - Regardless of feature size
47. 47
• Actual Dimension vary from MMC limit to
LMC limit
• Worst assembly condition exist when
mating parts at MMC
• Functional assembly requirements can be
related to actual dimension by symbol
in the drawing
M
50. 50
Exercises:
1.Number of Fundamental Deviations as per latest
standards? 28 (including cd,ef&fg)
2.The standard applicable for unspecified
dimensional tolerances in IS is?
51. 51
2.The standard applicable for unspecified
tolerances in IS is? IS:2102
3.The fundamental deviation for H7 is…
53. 53
4. H7 / p6 is interference fit.
5. H7 / g6 is ……………. Fit.
54. 54
5. H7 / g6 is clearance Fit.
6. H7 / m6 is ……………. Fit.
55. 55
6. H7 / m6 is transition Fit.
7. F7 / h6 is ……………. Fit.
56. 56
7. F7 / f6 is clearance Fit.
8. The difference between Upper Specification
Limit & Lower Specification Limit of a drawing
dimension is known as ………..
57. 57
8. The difference between Upper Specification
Limit & Lower Specification Limit of a drawing
dimension is known as Tolerance.
9.The reference temperature for measurement is
……. Deg C.
58. 58
9.The reference temperature for measurement is
20 Deg C.
10. All male feature dimensions are represented by
…………. Letters.
59. 59
10. All male feature dimensions are represented by
small letters.
