1. DRAFTING REVIEW ELEMENTS OF A DRAWING TYPES OF VIEWS PART DRAWINGS
ASSEMBLY DRAWINGS

2. INTRODUCTION
Drawings are constructed to strict standards to ensure a consistent interpretation.
Often part of a contractual document
Emphasis is on clarity and simplicity.
Generally prefer to use symbols over notes since manufacturer may not speak English.

3. PARTS OF A TYPICAL DETAIL DRAWING
revision
block
sheet
views
title
Block
(TOC)
notes

4. DRAWING SHEET SIZES North America International A 8.5”x11” A4
210mm x 297mm B
11”x17” A3
297mm x 420mm C
17”x22” A2
420mm x 594mm D
22”x34” A1
594mm x 841mm E
34”x44” A0
841mm x 1189mm
Choose sheet size such that drawing is filled but not crowded (based on number of views and dimensions needed).

5. REVISION BLOCK Used to track changes to the drawing.
Normally contains revision, description, date and approval.
Description often refers to a separate document typically called a “change order”.

6. TITLE BLOCK Contains important information about the part or assembly.
3rd angle projection symbol
Contains important information about the part or assembly.
Specific format is company-dependent but information shown above is commonly given.
3rd angle projection symbol important if drawing used internationally

7. DRAWING SCALE
Title block indicates scale which is predominantly used for views on drawing.
If a view uses a different scale it must be indicated under that view.
Scales are given as whole number ratios
interpret as (drawing unit) : (physical unit)
for scaling up: e.g. 2:1, 4:1, 10:1
for scaling down: e.g. 1:2, 1:5, 1:20
must have a 1 in the ratio. e.g. 2:3 not acceptable
Scale is chosen so that the features can be clearly seen.

8. NOTES
Gives useful information not covered by dimensions, symbols or in the title block.
Can also be used with arrows to indicate features of importance.
Current practice is to limit the use of notes since they may be misinterpreted.

9. DRAWING VIEWS
Only use the number of views necessary to convey information about the part (an isometric view is the exception)
Often need only two or three views
Edges which are visible in that view are shown as solid lines
Edges which are not visible are called hidden lines
Best not to show hidden lines
you cannot dimension to hidden lines anyway
they reduce clarity in drawings of complex parts

10. ORTHOGRAPHIC (PROJECTED) VIEWS
Primary views on a drawing.
Set of views at 90° to each other
Created by placing part in a virtual box and look through each side.
True size and shape
angles are correct
circles are round
lengths are to scale

11. ORTHOGRAPHIC VIEWS

12. ORTHOGRAPHIC VIEWS Views using first angle projection;
used in Europe and Asia
Views using third angle projection;
used in North America

13. ORTHOGRAPHIC VIEWS
3rd Angle Projection

14. ORTHOGRAPHIC STANDARD PRACTICE
Choose front view as most descriptive
Determine views to best represent object
Use minimum number of views to completely describe object
Views must be aligned
Views should not be labeled

15. AUXILIARY VIEWS It is an extra view of an object
It is used when the 6 principal views don’t describe an object (or some of its features) clearly or completely - in particular inclined features
Should not be labeled
It is used to show the true lengths of lines
It is used to show the true size of planes

16. AUXILIARY VIEWS

17. SECTION VIEWS
Useful to show interior features without using hidden lines
Must show section line in another view which indicates the cutting plane and the direction of view
Does not need to be aligned with parent view but often is shown aligned to enhance clarity
Must have unique letter label

18. SECTION VIEWS section line unique view label cutting plane surface
cross-hatched

19. DETAIL VIEWS
Used as enlargement of another view to enhance clarity of small features
Must show detail area in parent view with label
Is not aligned with parent view
Must have unique letter label and scale must be indicated since it is different from the parent view

20. DETAIL VIEWS
detail
area
with label
detail view with label
and scale

21. ISOMETRIC VIEW 3D view of part used to help visualization
Common if 3D CAD system used to develop drawing
Used only for a visual reference. Do not dimension this view.
Common now for assembly drawings.

22. ISOMETRIC VIEW
orthographic views
isometric view

23. CENTRE LINES
Used to indicate centres of full circles and axis of cylindrical features

24. DRAWING VIEWS IN SW
flange.sldprt
bracket.sldprt
shaft.sldprt

25. DRAWING VIEWS IN SW
shaft.sldprt

26. ASSEMBLY DRAWINGS
Assembly drawings show all the parts and how they go together.
Dimensions are not usually required.
A parts list or Bill of Material (BOM) specifies the item, quantity, description, part number, etc. for each part.
The item numbers from the parts list for each part are indicated using numbered balloons in the view.
Common styles used for assembly drawings:
as assembled view
section view
exploded view - Preferred!
Notes are used for assembly and machining instructions

27. ASSEMBLY DRAWING AS ASSEMBLED
BOM

28. ASSEMBLY DRAWING SECTION VIEW

29. ASSEMBLY DRAWING EXPLODED VIEW

30. DIMENSIONING

31. OUTLINE General Rules Linear Dimensions Angular Dimensions
Radial Dimensions
Diameter Dimensions
Holes
Tolerances

32. INTRODUCTION
Dimensions give size, location and details of all features of the part.
Manufacturing method is not specified but driven by dimensions, material and tolerances.
Dimensions are used per a standard to ensure consistent interpretation and clarity
Dimension standard often indicated on drawing in title block.

33. GENERAL RULES
Text height for dimensions and notes typically either .12” or 3 mm.
Text is always uppercase.
Units are usually either inches or millimetres.
If using inches:
no zero precedes decimal (.250)
dimensions expressed to same number of decimals as its tolerance (.250±.002)
If using millimetres:
zero precedes the decimal (0.5)
no trailing zeros are required (2±0.5, 3.25±0.1)
Dimension text is always horizontal.
Do not dimension to hidden lines.

34. LINEAR DIMENSIONS
dimension
line
visible gap
extension
line

35. DIMENSION PLACEMENT Dimensions are placed outside the part.
Do not crowd dimensions and avoid crossing dimension lines with extension lines.
space
space
aligned

36. ANGULAR DIMENSIONS

37. RADIAL DIMENSIONS Small radii are called fillets.
Preference is to use unlocated centres (easier to measure)
Unlocated Centre
Located Centre
radius
symbol
leader line
centre
mark

38. RADIAL DIMENSIONS Never dimension to radii tangent points.

39. DIAMETER DIMENSIONS large diameter diameter symbol small diameters
(arrows don’t fit inside)
centreline

40. HOLE DIMENSIONS
Multiple holes are common on parts so standardized symbols have been adopted.
Thru Hole
Thru Hole
Blind Drilled Hole
Blind Drilled Hole
depth
symbol
depth of full
diameter
note drill
point

41. COUNTERBORED HOLES Thru Hole Blind Hole counterbore diameter & depth
symbol
Note: depths always
measured from top surface

42. COUNTERSUNK HOLES Blind Hole countersink diameter & angle countersink
symbol
again hole depth
measured from top
surface

43. THREADS Standards used to describe threads.
Notes with leader are used to describe thread standard and dimensions.
External Thread
(Screw)
Internal Thread
(Threaded Hole)

44. EXTERNAL THREADS ON DRAWINGS
metric standard
major diameter
pitch
Metric
Thread
Minor diameter
shown as hidden
chamfer
major diameter
standard
American
Thread
threads/inch
(1/pitch)

45. THREAD HOLES ON DRAWINGS
Threaded holes are made by first drilling a plain hole and then forming the threads using a tool called a tap.
Size of drilled
hole given in
tables in
Machinery’s
Handbook
Thru Hole
Blind Hole
Major diameter
shown as
hidden
Usually show
section view for
blind threaded
holes.
must be at
least 4 threads
deeper

46. TOLERANCES
All real-world parts have variation in their features so every dimension on the drawing must indicate the allowable variation.
use of title block general tolerance note reduces clutter in drawing
The level of accuracy required is dictated by the fit & function of the design.
Tight tolerances = $$
Designers try to use generous tolerances on non-critical features.

47. COST OF TOLERANCES

48. TOLERANCE REPRESENTATION
Several ways:
Limits:
Bilateral:
Unilateral:
Single Limit:
Reference Only:
(no tolerance)
25.0
24.8
24.9±0.1
-0.2 25
25 MAX
(25)

49. DIMENSIONING TECHNIQUES
Must give position and size of each feature but only once on the drawing.
do not dimension the same feature again in a different view unless dimension for reference only
Dimension based on the function of the feature.
Dimension to reduce tolerance stack-up for critical features.
Always dimension position of holes to their centre not their edge.
Tolerance scheme in the solid model may not be suitable for the drawing.

50. OVER DIMENSIONED

51. REPEATED FEATURES
Repeat symbol

52. WHAT IS WRONG?
lever.sldprt

53. WHAT IS WRONG?

54. WHAT IS WRONG?

55. WHAT IS WRONG?

56. WHAT IS WRONG?

57. WHAT IS WRONG?

58. WHAT IS WRONG?
flange.sldprt

59. WHAT IS WRONG?

60. WHAT IS WRONG?