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DRAFT REQUIREMENTS
All walls on castings that are perpendicular to the parting plane require draft
or taper. This draft is not constant. It will vary with the length of draw (L).
The sketches below apply to all surfaces except cored holes and pockets.
A drawing may not show
draft. Standard foundry practice is to add draft to the part. To avoid
misunderstanding this is synonymous with saying it will add metal to the
casting, thereby increasing its size and weight.
Draft will normally be added at the parting line to features
perpendicular to the parting line.
Draft may be removed, but must be specified on the drawing. In holes, draft
will be added at the depth of the hole decreasing its
size. When a designer desires a hole dimension to become larger for reasons such
as clearance, he should so indicate.
The direction in which draft is applied is governed by the location of the
parting line and will be at the foundry's option unless otherwise specified.
When a parting line interrupts a surface to which draft is applied, the amount
of draft to be added will be determined by the longer portion of surface to be
drawn. Drafts will be applied to the remainder of the surface to provide a match
at the parting line.
|
Length of Draw (inches) |
Inches of Draft |
Degrees of Draft |
|
0.1 |
0.030 |
15 |
|
0.2 |
0.030 |
10 |
|
0.3 |
0.030 |
7 |
|
0.4 |
0.030 |
5 |
|
0.5 |
0.030 |
3 |
|
1 |
0.030 |
2 |
|
2 |
0.042 |
1 |
|
3 |
0.052 |
1 |
|
4 |
0.060 |
1 |
|
5 |
0.068 |
1 |
|
10 |
0.096 |
1 |
|
