Achieving the correct radius requires the right tooling press brake, and determining this can be a tricky process given the number of factors which come into play. This week, we run through a few key tips you should use to inform your tooling selection procedure for air bending.


When it comes to cold rolled steel, follow the 8X rule

Typically, it’s always best to choose a die opening width which is eight times the thickness of the material you are working with. This tends to produce the best working results, helps to ease forming, and ensure bend angle stability all whilst working within tonnage requirements.


The 20% is useful for calculating bend reductions in all material types

It’s useful for defining the inside radius in air bending over a die and calculating bend deductions, however, it does not take into account spring back or tonnage limits and is therefore not suitable for developing a die opening.

If the bend radius is larger than the 1-to-1 ratio through the 20% rule, don’t panic

One you’re found the right die width and calculated the bend radius using the 20% rule, you’ll probably find that the actual radius will be slightly higher than the material thickness. Provided the difference is small, this isn’t a problem as short of custom tooling or stamping, it’s almost impossible to achieve a precise 1-to-1 ratio.

The inside bend radius should never be less than the minimum sharp bend radius

If this rule isn’t followed, the bend turns sharp, the punch will dig a ditch into the material. When this happens, it becomes impossible to physically achieve the inside bend unless you resort to stamping or bottoming. You need to aim for a one to one material thickness ratio and this can be easily achieved provided your press brake can handle the tonnage.


ACRA are established sheet metal fabrication industry suppliers specializing in quality new and used machinery including press brake tooling and dies. We currently have an extensive range of quality press brake tooling dies from our Italian supplier, so now is the perfect time to expand your tooling library by investing in some new dies. To learn more about our capabilities, please don’t hesitate to get in touch with us by calling (03) 9794 6675.