Minimum Bend Radius Calculator

Figure 1
Cracking on the outside surface is caused by
using too small of an inside bend radius


This calculator predicts what the minimum bend radius should be to avoid chacking or orange peeling on the outside radius of the bend. Here again, a “Minimum Bend Radius” is not necessarily the same thing as a “Sharp bend.

A Sharp bend will always be less than a Minimum bend radius but, a Minimum Bend radius does not need to be sharp.

Minimum Bend Radius

What is the minimum radius? It is the smallest inside bend radius that you can place in a piece of material before the tensile forces on the outside of the bend begin to tear the grains in the material apart. It is normally expressed in terms of multiples of the material thickness, e.g. 1t, 2t, etc. If the punch nose radius is sharp enough it can even pull the grains apart when bending perpendicular to the grain.

The effect is most commonly seen in bends that run parallel to the materials grain, or the direction off roll. Once that separation begins to occur the bend to bend variations in angle and dimension will increase, sometimes dramatically.

You will also need to visit Matweb.com, another similar site, or material reference guide for the pieces of data that are required for the calculator to work correctly. In this case, you will need to find:

Material Tensile Strength in psi.

Material Thickness in inches

Area of Reduction as a precentage

Optional Die Opening in inches


Minimum Bend Radius Calculator


Try our Springback Calculator and our Sharp Bend Indicator


Please leave a comment on the calculator; what you thought about it, along with suggestions on how we might improve it.


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