Bend allowance formulas

What is the material? For 5052 H32 sheet aluminum I used the rule of thumb bend allowance = thickness of the material for a 90 degree bend. That is, for .063" thick the bend allowance was 1/16 inch. This is based on stretch so it follows that a lesser angle requires less allowance.

Other metals behave differently. I remember 340 or 360 stainless steel needed slightly less (more? it is hard to remember, it was a very long time ago) bend allowance because its radius was naturally more rounded. Aircraft aluminum would crack if its bend radii was as tight as I used for the more ductile aluminum, so it too used somewhat less allowance and could not necessarily be trusted with 90 degrees bends.

Please keep in mind that material stretch does also get impacted by the force and gap between the jaws of the press brake. That might impact your bend allowance too. ncalculators claims to have an algorithm that can give you a precise figure. You will need to know the "K-Constant" for the metal you are working with. I hope these sites give you accurate information.

I hope this helps.