1. Dimensioning

2. Why do we dimension drawings?
Dimensioning
Why do we dimension drawings?
In order to provide accurate size description of a part for manufacturing.
To describe the relationships between features in your drawing.

3. There Are 2 Basic Types of Dimensions
Dimensioning
There Are 2 Basic Types of Dimensions
Size Dimensions
Location Dimensions

4. 5 Basic Rules to Remember
Dimensioning
5 Basic Rules to Remember
Start Small, Go Big
Do Not Dimension to Hidden Lines or Hidden Features
Avoid Placing Dimensions on Part
Place Dimensions Between Views
Do Not Dimension to Edge of Arcs

5. Dimensioning Key Terms Dimension Line Extension Line Finish mark
Leader Dimension
Offset
Centerline
Finish mark
Dimension Value
Baseline Dimensioning
Chained Dimensioning

6. Dimensioning
Key Terms

7. Dimensioning Key Terms Tolerance
The total allowable variation a part can have
from the specified dimension.
The less variation allowed, the more the part
will cost to make.

8. Dimensioning
Leaders

9. Orientation for Dimension Values
Dimensioning
Orientation for Dimension Values
Unidirectional:
read horizontally from bottom of sheet
Aligned:
align with dimension line and read from bottom or right side of sheet

10. Unidirectional Orientation
Dimensioning
Unidirectional Orientation

11. Dimensioning
Aligned Orientation

12. Stagger Dimension Values
Dimensioning
Stagger Dimension Values

13. Dimension & Extension Lines
Dimensioning
Dimension & Extension Lines

14. Dimensioning
Finish Marks

15. Dimensioning Choice of Dimensions
The dimensions you specify determine the way the the part is manufactured and the way the tolerance is applied
Fully dimension each part
Do not over dimension,
Each dimensions should appear only once

16. Choosing Which Dimensions to Show
Dimensioning
Choosing Which Dimensions to Show
Don’t over dimension!
Give the diameter of circular shapes.
Give the radius of arcs.
No redundant dimensions
Give size dimensions for features.
Give location dimensions to show how features relate to one another.

17. Effect of Tolerance on Dimensioning
Chained
Each dimension continues from the previous one
Tolerances stack
Baseline
Each dimension is specified from a common baseline
Tolerances do not stack

18. Dimensioning Units Metric
Metric values are typically given in whole millimeters or to one decimal place. 3
3.5

19. Placement of Dimensions
Dimensioning
Placement of Dimensions
The rules for dimension placement help ensure that others will be able to interpret your drawing
Where placement practices conflict, remember that your goal is to clearly communicate the purpose of the drawing. Use the practice you feel will make the drawing easy to understand.

20. Dimensioning Placement Practices
Avoid dimensioning on object (face of part).
Avoid dimensioning to hidden lines.
Place dimensions between views when possible.
Group dimensions around a central view.
Place dimensions where feature shows shape.
Dimension from or between machined surfaces
Give overall dimensions where possible.

21. Dimensioning
Dimensioning Holes

22. Dimensioning
Using Diameter Symbol

23. Dimensioning
Locating Holes

24. Dimensioning
Summary
Dimensioning drawings correctly can be as important or more important than drawing the shapes correctly.
Good dimensioning requires practice and thought!