1. CHAPTER 4
Dimensioning

2. Content
Overview
Terminology
Basic Concept
Standard Practice
Detail Dimensioning
Dimensioning Technique

3. MEMB113 | MANUAL DRAWING | CHAPTER 4
4.1 Overview
Dimension is a way of displaying the size information and feature location on a drawing
Generally consist of lines and number:
dimension lines
extension lines
leader lines
number to indicate the measurement
Dimension 20
Dimension line
Extension line 4 8 R6

4. The dimension should not be redundant / over dimension
MEMB113 | MANUAL DRAWING | CHAPTER 4
4.1 Overview
Proper dimensioning should give enough information to manufacture the component
The dimension should not be redundant / over dimension
Example of redundant
dimensioning

5. Designs are dimensioned based on two criteria:
MEMB113 | MANUAL DRAWING | CHAPTER 4
4.1 Overview
Designs are dimensioned based on two criteria:
Basic sizes and locations of features
Details for construction and for manufacturing
The unit of measurement should be consistent – mm or inches
ALL DIMENSIONS IN MM
- should be written on drawing

6. 4.1 Overview Generally two types: Linear dimension: in mm
MEMB113 | MANUAL DRAWING | CHAPTER 4
4.1 Overview
Generally two types:
Linear dimension: in mm
Angular dimension: in degree, minutes and seconds
Linear dimension
Angular dimension

7. MEMB113 | MANUAL DRAWING | CHAPTER 4
4.2 Terminology

8. 4.3 Basic concept Size dimension Location dimension
MEMB113 | MANUAL DRAWING | CHAPTER 4
4.3 Basic concept
Size dimension
May be the overall width of a part or the diameter of a hole
Location dimension
May be the length from the edge of an object to the center of a feature
Size and location dimensions are used to
describe parts for manufacture

9. 4.3 Basic concept Basic criteria
MEMB113 | MANUAL DRAWING | CHAPTER 4
4.3 Basic concept
Basic criteria
“What info necessary to manufacture or construct the object?”
E.g. to drill a hole, need to know
The diameter of the hole
The location of the center
The depth of the hole

10. 4.3 Basic concept Dimensions showing the location and
MEMB113 | MANUAL DRAWING | CHAPTER 4
4.3 Basic concept
Dimensions showing the location and
orientation of features, such as the
location of the center of the hole
Dimensions showing the size of features,
such as the height and depth of the part
and the diameter of the hole

11. 4.4 Standard practice Dimension
MEMB113 | MANUAL DRAWING | CHAPTER 4
4.4 Standard practice
Dimension
the numerical value that defines the size, shape, location, etc. of a feature.
Normally height – 3mm and space between line – 1.5mm 20 8 R6 4

12. 4.4 Standard practice Dimension line Placement
MEMB113 | MANUAL DRAWING | CHAPTER 4
4.4 Standard practice
Dimension line
A thin solid line that shows the extent & direction
Broken for the placing numbers
Placement
Dimension placement depends on the space available
Should follow the standard practices

13. MEMB113 | MANUAL DRAWING | CHAPTER 4
4.4 Standard practice
EITHER OR

14. 4.4 Standard practice Reading direction
MEMB113 | MANUAL DRAWING | CHAPTER 4
4.4 Standard practice
Reading direction
All dimensions and note text must be orientated to read from the bottom of the drawing

15. 4.4 Standard practice Arrows Extension line Visible gap
MEMB113 | MANUAL DRAWING | CHAPTER 4
4.4 Standard practice
Arrows
Symbols at end of dim. Lines to show limits of the dim.
Uniform in size & style, usually 3mm long & 1/3 as wide
Extension line
A thin solid line perpendicular to dim. line, indicating which feature is associated with dim.
Visible gap
There should be visible gap of 1mm between feature and extension line

16. 4.4 Standard practice Leader line Diameter symbol Radius symbol
MEMB113 | MANUAL DRAWING | CHAPTER 4
4.4 Standard practice
Leader line
- A thin solid line to indicate the feature with which a dimension, note or symbol is associated
Diameter symbol
Radius symbol
Tolerance

17. 4.4 Standard practice Spacing
MEMB113 | MANUAL DRAWING | CHAPTER 4
4.4 Standard practice
Spacing
The minimum distance from the object to first dim. is 10mm
Min. spacing between dimensions is 6mm
Should be visible gap between extension line and the feature it refers
Extend beyond dimension lines 2mm
Minimum dimension
line spacing

18. Grouping and staggering
MEMB113 | MANUAL DRAWING | CHAPTER 4
4.4 Standard practice
Grouping and staggering
Dimensions should be grouped for uniform appearance
Do not use object lines as part of your dimensions
Group dimensions

19. 4.4 Standard practice Extension line
MEMB113 | MANUAL DRAWING | CHAPTER 4
4.4 Standard practice
Extension line
Used to relate a dim. to one or more feature, and usually drawn perpendicular to feature & dim. line
The center of a feature, such as a hole, is located by making the center lines extension lines for the dimension. Extension lines can also cross to mark a theoretical point

20. MEMB113 | MANUAL DRAWING | CHAPTER 4
4.4 Standard practice
Extension line should not cross dim lines, are not broken when crossing object or other extension lines, and are broken when crossing arrows

21. 4.4 Standard practice View dimensioning
MEMB113 | MANUAL DRAWING | CHAPTER 4
4.4 Standard practice
View dimensioning
Dimensions should be kept outside the object
Dimension outside the view

22. 4.4 Standard practice Repetitive feature
MEMB113 | MANUAL DRAWING | CHAPTER 4
4.4 Standard practice
Repetitive feature
The symbol x is used to indicate the number of times a feature is to be repeated
Repetitive feature

23. Staggered dimensioning
MEMB113 | MANUAL DRAWING | CHAPTER 4
4.4 Standard practice
Staggered dimensioning
A part dimensioned using coordinate dimensions,
with a baseline or datum surface as a starting point

24. 4.4 Standard practice Stagger dimension text
MEMB113 | MANUAL DRAWING | CHAPTER 4
4.4 Standard practice
Stagger dimension text

25. 4.4 Standard practice Others Avoid dimension to hidden lines
MEMB113 | MANUAL DRAWING | CHAPTER 4
4.4 Standard practice
Others
Avoid dimension to hidden lines
The extension line can cross each other, but not dimension line
The extension line can cross the object, but not the dimension line
Avoid dimensioning inside of object
Centre line cannot be used as dimension line, but can be extended as extension line

26. Foreshortened leaders
MEMB113 | MANUAL DRAWING | CHAPTER 4
4.5 Detail Dimensioning
Dimensioning circle
Dimensioning arc
Foreshortened leaders
Dimensioning arcs

27. Dimensioning a blind hole
4.5 Detail Dimensioning
Dimensioning hole
Dimensioning a blind hole

28. 4.5 Detail Dimensioning
Counterbore and
countersink hole

29. Dimensioning keyways & keyseats
MEMB113 | MANUAL DRAWING | CHAPTER 4
4.5 Detail Dimensioning
Dimensioning keyways & keyseats
Dimensioning slots

30. Dimensioning chamfers
MEMB113 | MANUAL DRAWING | CHAPTER 4
4.5 Detail Dimensioning
Dimensioning chamfers

31. 4.6 Dimensioning Technique
MEMB113 | MANUAL DRAWING | CHAPTER 4
4.6 Dimensioning Technique
Geometric breakdown technique

32. MEMB113 | MANUAL DRAWING | CHAPTER 4
Example of the steps to create a dimensional drawing

33. MEMB113 | MANUAL DRAWING | CHAPTER 4
Summary of current and previous ASME standard dimensioning ysmbol
Contour dimensioning

34. End of Chapter 4
Thank You