Calculating Bend Allowance For Sheet Metal

Most sheet metal materials will conform to the calculations.

Calculating bend allowance for sheet metal.

You will need to know your material thickness mt the bend angle b the inside radius ir and the k factor k. The bend allowance and bend deduction are two measures that relate the bent length of a piece of sheet metal to the flat length. This page also includes a link to a on line sheet metal bend allowance calculator. To calculate r which is the radius of the arc on the neutral axis we can use the following equation.

If you have a sheet metal bending product as shown in above picture with two legs of length x and y and you unbend it you will see that total length of the unbend sheet will not x y rather the length will be x y ba. The bend allowance describes the length of the neutral axis between the bend lines or in other words the arc length of the bend. When bends are made smaller than the required min. Most sheet metal materials will conform to the calculations.

The following illustration shows the equation calculation for determining the bend allowance when forming sheet metal. And by having t and the sheet thickness t we can calculate the k factor as follow. Therefore the bend allowance added to the flange lengths is equal to the total flat length. The bend allowance formula takes into account the geometries of bending and the properties of your metal to determine the bend allowance.

Now that we have both leg length 1 and 2 we can use the following equation again to calculate the bend allowance. Radius of a bend is determined by the hardness and thickness of the metal. Where ba is bending allowance. The material thickness will be measured in decimal form not by the gauge number.

The most important considerations when bending metal is the min. Radius metal will crack at the outside heel of the bend. A is the bending angle in the above equation so. To calculate the neutral axis distance from the inner face t we can subtract inside bend radius from r.