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 |