Understanding Sheet Metal Bend Radius
Sheet metal bend radius is the inside curve formed during bending. It controls shape, strength, and flat pattern accuracy. A radius that is too tight can crack the sheet. A radius that is too large can change the final part size.
Why Bend Radius Matters
Every sheet has thickness, hardness, and grain direction. These details affect how far metal can stretch. Mild steel can often use a radius near one thickness. Stainless steel usually needs more room. Some aluminum grades need a wider bend. The calculator helps compare these choices before cutting material.
Key Shop Measurements
The inside bend radius is measured from the bend center to the inside face. The outside radius adds the sheet thickness. The neutral axis sits between them. It does not stretch as much as the outer surface. The k factor locates that neutral axis. A common value is 0.33. Softer tools or larger radii may need a higher value.
Flat Pattern Planning
A formed part starts as a flat blank. The blank length must include bend allowance. Bend allowance is the arc length along the neutral axis. Bend deduction removes the excess created when two outside flange lengths meet at a bend. Accurate values reduce trial parts. They also save time on press brake setup.
Tooling and Material Choices
Air bending often creates a radius related to the V die opening. Bottoming and coining can force a radius closer to the punch nose. Grain direction also matters. Bending across the grain is safer. Bending with the grain raises the cracking risk. Use a larger radius when the material is hard, old, or unknown.
Using The Result
This calculator gives a practical estimate for layout work. It should not replace shop tests. Real parts can vary because of tool wear, coating, rolling direction, and springback. Use the warning message when the entered radius is below the recommended minimum. Save the CSV or PDF report for job notes. For critical parts, bend a sample coupon first. Keep one unit system for each job. Record the die opening, punch nose, and measured angle. Reuse proven settings when the same gauge returns. This improves repeatability across batches and operators and reduces scrap.