BendTab

Sheet metal cut to the two outside measurements on the drawing comes out of the bender a few millimetres too long. The bend eats part of the length, and how much depends on the thickness of the metal and the curve of the bend. BendTab works out that difference before the cut, as a bend allowance or a bend deduction.

The main calculator asks for thickness, inside radius, bend angle and a K-factor, a number for where inside the metal the length stays the same during bending. Next to the inputs, a drawing shows the bend's cross-section, and the formula is printed under the result. The privacy page says the numbers are worked out on your device rather than on an application server.

A second calculator unfolds an L-shaped part with one bend into its flat length. A third works back to the K-factor from a test piece you bent and measured, so later parts from the same material and tooling start from a real value. Results switch between millimetres and inches, and the last calculation per tool can be saved in the browser.

The methods page asks for a test bend under the same conditions before a result goes into production. The site also holds gauge charts for four sheet materials and charts for drill sizes, tap drills and fractions. Each gauge table names its supplier source and the date its values were checked.