This week, we continue navigating the complex process of choosing the right die for your press brakes. Here are two more important formulas you can use to inform your tooling selection for air bending.


Select a die opening half the working value of the die

To ensure your die are used at an optimal rate, it’s best to use it at half of the maximum working rate. This can be determined by finding a die opening where the bend occurs halfway down the die face which you can find through the formula:

(outside bend radius x0.7071) x factor


Calculating the outside radius can be done by adding the inside ben radius you need to the material thickness. The factor in the formula refers to a multiplier around 4.0 inches which will give you a geometrically perfect bend, but does not allow for spring back, so you’ll need to increase the multiplier slightly to around 4.85 for materials with a thickness less than 0.125 in. and 5.85 in for materials between 0.125 and 0.250 in. If you have a material thicker than 0.250inches, the calculation changes. Using this formula will keep the relationships consistent regardless of radius size and material thickness ratios.

Use [(575 x material thickness2 )/die opening] x material factor to determine tonnage per foot

This is based of a 60,000 PSI tensile AISI 1035, but the factor for a specific material can be obtained through a comparison of tensile strength. This can be done by dividing the tensile strength of your material by 60,000 and then insert the resulting number into the ‘material factor’ part of the equation. The length of the bend also needs to be looked at to ensure you’re within the tonnage limits of your press brake.


If formulas aren’t your thing, it is possible to use software

Automated calculation software is increasingly common within the press brake tooling industry, and there are a number of quality software packages available from brands such as SomaBEND and Cincinnati Incorporated.


ACRA are proud to supply operators in the sheet metal industry with quality new and used machinery. Our range encompasses both press brakes and tooling dies. We recently received a number of quality new press brake tooling dies from our Italian supplier, Euram Tooling, so now is the perfect time to invest and expand you tooling library. To learn more about our capabilities, please don’t hesitate to get in touch by calling (03) 9794 6675.