Bend Deduction
The amount subtracted from the sum of two flange outside dimensions to get the flat blank length.
What it means on the floor
Bend deduction (BD) is the practical complement to bend allowance. Instead of adding the neutral-axis arc to flat flange lengths, you take the two outside flange dimensions, add them, and subtract the bend deduction to get the blank size.
Bend deduction equals twice the outside setback minus the bend allowance. Many shops prefer working in bend deduction because the outside dimensions are what appear on most prints.
Category: Forming
Applying the term
Interpret Bend Deduction in the context of the drawing, governing standard, and customer requirement in front of you — the same word can carry different limits in design, quality, and production documents. Check whether a stated value is nominal, minimum, maximum, or reference-only, and whether it applies before forming, after forming, or after heat treatment.