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Bend Deduction
BEND DEDUCTION: Bend Deduction is the difference from the start of the radius to the apex of the angle times two minus the bend allowance. To state it simply: Bend deduction = D + D - bend allowance              D =  tan(A°÷ 2) x (MT + BR) Note! The formulas can be entered in the calculator (optionally purchased) exactly how they are written down. Remember mathematical hierarchy?
Bend deduction 90 deg. angle = 2(MT + BR) - Bend allowance Bend deduction = 2 x (tan(A°÷ 2) x (MT + BR)) - Bend allowance
SETBACK: Distance equal to half of a bend deduction which          places a brake punch die right on the center of a bend