Bend allowance and bend deduction calculations are methods you can choose to determine the flat length of sheet stock to give the desired dimension of the bent part. Other methods include bend tables, K-Factor, and bend calculation.
Bend Allowance and Bend Deduction Calculations
The following equation is used to determine the total flat length when bend allowance values are used:
Lt = A + B + BA
The following equation is used to determine the total flat length when bend deduction values are used:
Lt = A + B - BD
where:
- Lt is the total flat length
- A and B are shown in the illustration
- BA is the bend allowance value
- BD is the bend deduction value
Bend Allowance and Bend Deduction Value
You can specify an explicit bend allowance or bend deduction for any sheet metal bend by entering the value when you create the bend.
By definition, the bend allowance is the arc length of the bend as measured along the neutral axis of the material. By definition, the bend deduction is the difference between the bend allowance and twice the outside setback.
