Dimension and Tolerancing

1. Precision Dimensioning
Engineering II

2. Dimensioning Rectangular Prisms

3. Dimensioning Cylinders
• The diameter of
cylinders should be
dimensioned in the
rectangular view
(not the circular
view).
• Cylinders without a
hole passing
through them only
require one view.

4. Dimensioning Cones

5. Dimensioning Spheres

6. Rectangular Coordinate Dimensioning
• Used when computer-controlled production
machines are used to manufacture parts.
• The designer should consult with personnel in
manufacturing to ensure that the origin is
located in an appropriate position.
• Two types of rectangular coordinate
dimensioning:
– Coordinate Dimensioning with Dimension Lines
– Coordinate Dimensioning Without Dimension
Lines

7. Coordinate Dimensioning with
Dimension Lines

8. Coordinate Dimensioning without
Dimension Lines

9. Tabular Dimensioning
• Tabular dimensioning is used when a
series of parts consists of the same
features or geometry but vary in
dimension.
• Letters are used in place of dimension
values, and the values are then placed
in a table.
• Most standard parts are dimensioned
this way in catalogs, the machinery
handbook, and in the back of most
textbooks.

10. Tabular Dimensioning

11. Dual Dimensioning – Position Method
• Millimeter value is placed above (or
below) the inch value or separated by a
dash.

12. Dual Dimensioning – Bracket Method
• Millimeter value is enclosed in square
brackets. A note should be placed on the
drawing such as: DIMENSIONS IN [ ]
ARE MILLIMETERS.

13. Tolerance Dimensioning
• Why do we need tolerance
dimensioning?
– Interchangeable parts manufacturing
– Parts are manufactured at widely separate
localities
– Effective size control
– Modern industry relies on it for
subcontracting and replacement parts
• Accuracy is Expensive, however

14. Reading Dimensions
.1 One tenth of an inch
.01 One hundredth of an inch
.001 One thousandth of an inch
.0001 One ten-thousandth of an inch
.00001 One millionth of an inch

15. Specification of Tolerances
Bilateral-Equal
Limit Dimension
Bilateral-Unequal
Unilateral

16. Tolerance
• Tolerance is the total amount a specific
dimension is permitted to vary
(difference between the maximum and
minimum limits).
• The dimension below has a tolerance of
.0003.

17. Maximum Material Condition
• When specifying tolerance dimensions,
the maximum material condition
(MMC) means the product or part
contains the maximum amount of
material specified by the tolerance.
• The heaviest part.

18. Maximum Material Condition
• For the part shown here the MMC is
1.4996 since that size would yield the
most material.

19. Allowance
• Allowance is the minimum clearance or
maximum interference intended
between the maximum material
condition (MMC) of mating parts.
• The allowance for the system below is:
25.000 - 24.890 = 0.110

20. More Terminology
• Nominal Size - General identification in
fractions (ex. 1-1/2 for 1.500).
• Basic Size - General identification in
decimal (ex. 1.500).
• Actual Size - Measured size.
• Limits - Maximum and minimum sizes
indicated by the tolerance dimensions.

21. Clearance Fit
• Space is always left between parts.
• What is the allowance in this case?
• 1.5000 – 1.4988 = .0012

22. Interference Fit
• Always an interference of material.
• What is the allowance in this case?
• 1.5000 – 1.5013 = -.0013 or just .0013

23. Transition Fit
• Fit might result in clearance or interference.

24. Line Fit
• Clearance or surface contact may result at
assembly.

25. Basic Hole System (Hole Basis)
• The minimum size hole is taken as the basic
size.
• Used when standard tools are used to produce
holes (reamers & broaches).

26. Basic Shaft System (Shaft Basis)
• The maximum shaft size is taken as the basic
size.
• When several parts having different fits, but
one nominal size are required on a single shaft.

27. Specifying a Fit - Inches
Nominal
Size Range
Inches
Over To
Class RC 1
Limits
of
Clear.
Standard
Limits
Hole
H5
Shaft
g4
0-0.12
0.1
0.45
+0.2
–0
–0.1
–0.25
0.12-0.24
0.15
0.5
+0.2
–0
–0.15
–0.3
0.24-0.40
0.2
0.6
+0.25
–0
–0.2
–0.35
0.40-0.71
0.25
0.75
+0.3
–0
–0.25
–0.45
0.71-1.19
0.3
0.95
+0.4
–0
–0.3
–0.55
1.19-1.97
0.4
1.1
+0.4
–0
–0.4
–0.7
• Determine type of fit
and find corresponding
table
• Determine basic size
• Find size range on
table
• Determine tolerances
for Hole and Shaft
• Remember values are
in thousandths of an
inch.

28. Specifying a Fit - Inches
Nominal
Size Range
Inches
Over To
Class RC 1
Limits
of
Clear.
Standard
Limits
Hole
H5
Shaft
g4
0-0.12
0.1
0.45
+0.2
–0
–0.1
–0.25
0.12-0.24
0.15
0.5
+0.2
–0
–0.15
–0.3
0.24-0.40
0.2
0.6
+0.25
–0
–0.2
–0.35
0.40-0.71
0.25
0.75
+0.3
–0
–0.25
–0.45
0.71-1.19
0.3
0.95
+0.4
–0
–0.3
–0.55
1.19-1.97
0.4
1.1
+0.4
–0
–0.4
–0.7
• RC1 - Close Sliding Fit
• Basic size of 1.500
• Upper tolerance on
hole is +0.4, which is
really +0.0004
• Lower tolerance on
hole is -0.
• Upper tolerance on
shaft is -0.0004
• Lower tolerance on
shaft is -0.0007

29. Specifying a Fit - Inches
Nominal
Size Range
Inches
Over To
Class RC 1
Limits
of
Clear.
Standard
Limits
Hole
H5
Shaft
g4
0-0.12
0.1
0.45
+0.2
–0
–0.1
–0.25
0.12-0.24
0.15
0.5
+0.2
–0
–0.15
–0.3
0.24-0.40
0.2
0.6
+0.25
–0
–0.2
–0.35
0.40-0.71
0.25
0.75
+0.3
–0
–0.25
–0.45
0.71-1.19
0.3
0.95
+0.4
–0
–0.3
–0.55
1.19-1.97
0.4
1.1
+0.4
–0
–0.4
–0.7

30. Specifying Fits - Metric
Basic
Size
Loose Running
Hole
H11
Shaft
c11
Fit
1 Max
Min
1.060
1.060
0.940
0.880
0.180
0.060
20 Max
Min
20.130
20.000
19.890
19.760
0.370
0.110
25 Max
Min
25.130
25.000
24.890
24.760
0.370
0.110
• Determine type of fit
and find corresponding
table
• Determine basic size
• Find size range on
table
• Determine tolerances
for Hole and Shaft

31. Specifying Fits - Metric
Basic
Size
Loose Running
Hole
H11
Shaft
c11
Fit
1 Max
Min
1.060
1.060
0.940
0.880
0.180
0.060
20 Max
Min
20.130
20.000
19.890
19.760
0.370
0.110
25 Max
Min
25.130
25.000
24.890
24.760
0.370
0.110
• Loose Running Fit
• Basic size of 25