1. Engineering Graphics V
Prof. Jon Southen
October 20, 2008

2. Tolerancing

3. Tolerances Variations exist in all manufactured parts
Tolerances specify minimum and maximum allowable value of a dimension
Especially important for systems of with mating parts - if tolerances are exceeded, parts may not fit together

4. Tolerancing
Allowable variations or tolerances must be specified by the designer, with two objectives:
ensure fit and function
minimize manufacturing cost

5. Tolerancing Tolerances can drive the manufacturing process
e.g. a shaft must turn in a hole in a bearing
hole to .7512, shaft to .7492
function drives tolerance which then drives machining process used OR
The manufacturing process can drive the tolerance
What if drill press is only tool available to make the hole, and it can only deliver .748 to .754?

6. Tolerances of Different Manufacturing Processes

7. Tolerance – Specific Parts
If a part is dimensioned ± 0.003, it means that the part is acceptable within the range and 4.647
The upper and lower limits are called limit dimensions (4.653 and 4.647)
The tolerance is the difference between the limit dimensions ( – = 0.006)

8. Tolerance – Specific Parts
Plus and minus tolerance
e.g ± (bilateral tolerance)
e.g (unilateral tolerance)
Limit tolerance
Maximum and minimum sizes are specified directly
e.g.

9. Geometric Dimensioning and Tolerancing (GD&T)
GD&T symbols specify additional tolerancing information for 3D geometry
Used in addition to standard +/- dimensioning
Used properly, GD&T can allow looser tolerances to minimize manufacturing cost

10. GD&T symbols

11. Example

12. Working Drawings

13. Outline Definition of working drawings Some basics Detail drawings
Standard sheet size
Dimensioning standards
Drawing scale
Projection angle
Title blocks
Detail drawings
Assembly drawings
Examples

14. Elements of Engineered Products
Engineered products contain many parts:
Non-standard parts that must be made
Standard parts that can be ordered from catalogues
fasteners
bearings
gears
etc.

15. Working Drawings
“Working drawings are the complete set of standardised drawings specifying the manufacture and assembly of a product based on its design.”

16. Some Basics Drawings use standard sheet sizes
Specified dimensioning standards are used
Drawings are to a specified scale
Specified projection angle is used
First-angle (Europe) or third-angle (North America)

17. ANSI Standard Sheet Sizes
Metric (mm)
U.S. Standard
A4 210 x 297
A-Size 8.5” x 11”
A3 297 x 420
B-Size 11” x 17”
A2 420 x 594
C-Size 17” x 22”
A1 594 x 841
D-Size 22” x 34”
A0 841 x 1189
E-Size 34” x 44”
ANSI Standard Sheet Sizes

18. Dimensioning Standards
Specify appearance of arrowheads, dimension lines, text alignment, etc.
ANSI – North America
ISO – Europe
DIN – Germany
JIS – Japan
Etc.

19. Metric Scale Each view on a drawing has an associated scale
Unless otherwise specified, the drawing scale is used
1:1
Full size
1:2
Half size
1:5
Fifth size
1:10
Tenth size
1:20
Twentieth size
1:50
Fiftieth size

20. Title Blocks Drawing title blocks typically contain the following:
Name and address of company
Title of drawing
Drawing number
Names and dates of drafter, checker, etc.
Design approvals
Predominant drawing scale
Drawing sheet size
Weight of item
Projection angle
Sheet number (if multiple sheets used)

21. Title Block

22. Part and Drawing Numbers
Every part is assigned a unique part number for record keeping
This allows the same part to be used in different products
Every drawing is also assigned a unique number, also for record keeping

23. Other Required Information
Revision block
records revisions to drawing
CAD packages create these automatically
Tolerance specifications
assumed tolerances for all dimensions, unless otherwise specified on the drawing

24. Requirements for Working Drawings
Completely describe the parts
Show the parts in an assembly
Identify all the parts
Specify standard parts

25. Elements of Working Drawings
A set of working drawings typically includes:
Detail drawings of each nonstandard part
Assembly drawings showing all the standard and nonstandard parts in a single drawing

26. Detail Drawings Dimensioned, multi-view drawing of a single part
All information required for manufacture, including
Dimensions and tolerances
Material
Surface finish
Etc.

27. Dimensioned Detail Drawing

28. Example Detail Drawing

30. Assembly Drawings
Assembly drawings show all the parts and how they go together
Dimensioning is not usually required
Hidden lines usually omitted
3D CAD packages can generate assembly drawings directly from assembly models

31. Elements of an Assembly Drawing
All parts shown in one drawing
assembled view
sectioned assembly
exploded assembly
Parts list or bill of materials (BOM)
part ID, quantity, description, catalog number, etc.
Balloons
each part is identified by a numbered balloon, and referenced to the parts list
Machining and assembly instructions

32. Assembly Drawing

33. Exploded Assembly Drawing

35. Sectioned assembly

36. Example

37. Example

38. Example MicroLux Drill Press #81631 Assembly Drawing

39. Example Harley Sportster Transmission

40. Example: Geared Locomotive (1896)

41. Examples from Western’s Formula SAE Team
SolidWorks rendering of 2005 car

42. Formula SAE Shock Absorber