Apply for financingSheet bend
This bend allowance calculator finds the arc length of one bend and the flat length of two legs. The sheet metal bend calculator uses the inside radius, the thickness, the angle, and a K-factor you enter. It is one bend. A part with several bends needs one pass per bend.
Flat length
3.368in
Planning estimate from the numbers you enter. Coverage, density, waste and price are assumptions, not a supplier quote or an engineering specification.
How it works
The neutral radius is the inside radius plus the K-factor times the thickness. Bend allowance equals the angle in radians times that radius. Outside setback is the tangent of half the angle, times the inside radius plus the thickness. Bend deduction is two setbacks minus the allowance. Flat length is leg A plus leg B minus the deduction. A 90 degree bend, 0.125 inch inside radius, 0.060 inch material, and a K-factor of 0.44 has a bend allowance of about 0.2378 inch and a bend deduction of about 0.1322 inch. Legs of 1.5 and 2 inches flatten to about 3.368 inches. The K-factor is yours. Air bending and bottoming do not share one K. This page will not look up a die.
Formula
Setback = tan(angle ÷ 2) × (inside radius + thickness). Deduction = 2 × setback − allowance. Flat = leg A + leg B − deduction. The sheet metal bend calculator is that flat length.
Example
Allowance is about 0.2378 inch. Deduction is about 0.1322 inch. Flat length is about 3.368 inches. Change the K-factor and the flat moves.
Tips
A K near 0.33 to 0.50 is common, and 0.44 is only the default. Measure a test coupon if the flat has to hit a tolerance. Inside radius is the radius after the bend, not the punch radius, when those differ.
Equipment
Dengaro arranges financing for a press brake or other shop equipment. Flat length is not a loan amount.
Important questions
Allowance is the length of the neutral arc. Deduction is what you subtract from the two outside legs to get the flat. The bend allowance calculator shows both.
Run the page once per bend and add the flats carefully, or subtract each deduction from the sum of the outside dimensions. The form holds one angle.
The setback uses the tangent of half the angle. Half of 180 degrees is undefined for this flat-pattern method. Stay under 180.
Only if you bring it. The sheet metal bend calculator does not include a material chart. Type the K you have validated.
Financing built into the sale