Fabrication · 2024 · 10 — 4 min read
K-Factor and Bend Allowance: What Every Architect Should Know
Bend allowance isn't a fabrication footnote. It decides whether your folded geometry closes — or fails on the brake.
When sheet metal is folded, the material on the outside of the bend stretches and the inside compresses. Somewhere between them sits a neutral axis that does neither. Where that axis sits — expressed as the k-factor — determines how much flat material a bend actually consumes.
Why architects should care
Because if the flat pattern is cut without accounting for bend allowance, the folded part will not match the model. Holes drift, edges miss, panels that should close leave a gap. The geometry was right; the development was wrong.
A number, not a guess
The k-factor is not folklore — it is a property of the material and the tooling, typically between 0.3 and 0.5 for aluminum. Set it correctly in your unfolding tool and the flat pattern lands on the brake exactly where the model predicted. That is the whole job.