I am adding a helix spiral to an extruded metal part mostly inside extrusion to accept a screw. I need a 4-40 thread but not sure on how big to make the 3 sided polygon for the groove and the pitch size. Is there a standard table I gen get or a standard practice ? I will use 4-40, 6-32, 8-32 and 10-32 in my designs.

Bob