Question 1

How do I determine the correct K-factor for my material?

Accepted Answer

K-factor depends on material, thickness, bend radius, and bending method. Start with these defaults: Air bending — mild steel 0.33, stainless 0.35, aluminum 0.33. Bottoming — add 0.05-0.10 to air bending values. For accurate results, bend a test coupon, measure the flat pattern versus formed dimensions, and back-calculate K. CNC press brake controllers often have material-specific K-factor libraries.

Question 2

What is the 8T rule for V-die selection?

Accepted Answer

The V-die opening should be approximately 8 times the material thickness (8T) for standard air bending. For thinner material (<1.5 mm), use 6T; for thicker material (>6 mm), use 10-12T. A wider die opening reduces required tonnage but increases minimum bend radius and springback. Too narrow a die opening causes marking, excessive tonnage, and potential die damage.