Draft Requirements

Draft requirements for walls
All walls on diecastings normally vertical to the parting plane of the die require draft or taper. This draft is not constant. It will vary with alloy used and with the depth of the wall as indicated. The graph shown is for inside walls. The draft required on outside walls is approximately half that required on inside walls. The provisions shown do not apply to diecast lettering, engraving or honeycomb designs.

The values shown represent normal production practice at the most economical level. Greater accuracy involving extra close work or care in production should be specified only when necessary since additional cost may be involved.

Cored Holes

Holes cast in diecastings are produced by the use of cores. Efficient casting of cored holes requires consideration of the related factors of draft requirements and the depth / diameter ratio. The table below gives "Normal" figures for guidance on the depth / diameter ratio.

Alloy Diameter of hole in Millimetres
<4 4 5 7 10 13 16 19 25
Maximum Depth in Millimetres
Aluminium  Drill 8 10 14 20 26 32 38 50
Zinc  9 14 20 28 40 52 80 114 150
Magnesium  Drill 8 10 14 20 26 32 38 50

For cores larger than 25mm diameter, the diameter : depth ratio should be < 1 : 5

Given that the guidelines above are followed, then the total draft requirement for cored holes may be seen in the graph below.