Free Sheet Metal Bend Allowance Calculator
Calculate exact Bend Allowance (BA), Bend Deduction (BD), Outside Setback (OSSB), and flat blank length for precision press brake fabrication.
📐 Sheet & Bend Geometry
📊 Flat Pattern Layout Outputs
Recommended Tools & Equipment
Tested hardware and components for high reliability
Frequently Asked Questions
What is the standard K-Factor for mild steel?
The standard K-Factor for cold rolled mild steel in typical air-bending operations is approximately 0.40 to 0.42. For bottom-bending or coining where inner radius equals punch radius, K-Factor approaches 0.45.
Why does my bent part measure longer than the flat pattern calculation?
If your finished part measures larger than expected, your calculated Bend Deduction was too small, usually because the actual inside bend radius formed in the press brake V-die was larger than the CAD punch radius (due to material springback or large V-die width).
How do I choose the correct press brake V-die opening?
For mild steel up to 1/2 inch thick, the recommended V-die opening width is 8 times the material thickness (8T). For aluminum or soft metals, 6T is common; for high-strength steel or stainless steel, 10T to 12T is used to prevent cracking along the outer grain.
What is the difference between Bend Allowance and Bend Deduction?
Bend Allowance is the developed length of the bend curve itself. Bend Deduction is the difference between the sum of the outside flange legs and the flat sheet length. Most CNC punch and laser programming software uses Bend Deduction.