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Tricks of the Trade
Q: I am aware of the fact that in air bending, the inside of the bend is created by the V-opening. What criteria should I use to determine the appropriate punch tip radius?
A: In each of the illustrations below, the V-opening is .394” (10mm) and the material is .060” (1.5mm) mild steel. This V-opening yields an inside radius of .066” (1.67mm). Each of the punch tips shown can be used to create this bend. However, to ensure maximum punch life, it is best to use a punch with a tip radius that is slightly less than the inside radius yielded by the V-opening.
When bending a wide range of materials (i.e. 10-20 gauge mild steel), it is possible to use a single punch tip radius provided that the tip radius is smaller than the inside radius that will be created by the smallest V-opening. For example, the recommended V-opening for a 20 gauge mild steel is .236” (6mm), yielding an inside radius of .039” (.99mm). The recommended V-opening for a 10 gauge mild steel is .984” (25mm), yielding an inside radius of .164” (4.16mm). A punch with a .030” (0.8mm) tip radius could be used when air bending this range of material, as the tip radius is slightly less than the inside radius yielded by the smallest V-opening.
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