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 (Baseline Dimensioning)

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
Limit Dimension
Bilateral-Equal
Unilateral
Bilateral-Unequal

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

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 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: = 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 ).
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?
– = .0012

22. Interference Fit Always an interference of material.
What is the allowance in this case?
– = 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
Hole H5
Shaft g4
0-0.12
0.1
0.45
+0.2 –0
–0.1
–0.25
0.15
0.5
–0.15
–0.3
0.2
0.6
+0.25
–0.2
–0.35
0.25
0.75
+0.3
–0.45
0.3
0.95
+0.4
–0.55
0.4
1.1
–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
Hole H5
Shaft g4
0-0.12
0.1
0.45
+0.2 –0
–0.1
–0.25
0.15
0.5
–0.15
–0.3
0.2
0.6
+0.25
–0.2
–0.35
0.25
0.75
+0.3
–0.45
0.3
0.95
+0.4
–0.55
0.4
1.1
–0.4
–0.7
RC1 - Close Sliding Fit
Basic size of 1.500
Upper tolerance on hole is +0.4, which is really
Lower tolerance on hole is -0.
Upper tolerance on shaft is
Lower tolerance on shaft is

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

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