Sheet metal design rules that cut scrap + rework.
These sheet metal design guidelines are the rules of thumb our engineers use when they review your flat pattern. Limits vary with material, thickness and tooling, and we confirm them for yours before the job goes out for sourcing.
Design breaks a rule?
Send it anyway. Tight flanges and close holes aren’t automatic no’s. Our engineers review every flat pattern, flag what drives cost, and tell you what a change in radius, relief or hole location would save.
Quality + Compliance
AS9100D Compliant · ISO 9001:2015 · ISO 13485 Compliant · ITAR Registered · NIST 800-171 Compliant
Bends + flanges
Where most sheet metal scrap starts.
- Bend radius
- At least 1x material thickness.
- Consistent radii
- One radius per part where you can.
- Flange length
- At least 4x material thickness.
- Bend relief
- Width at least 1x thickness.
- Gauges
- Standard thicknesses quote faster.
- Grain direction
- Bend across it on harder alloys.
- Tolerance
- ±0.005" on cut features. ±0.015" across bends.
Holes + hardware
Keep features clear of the bend.
- Hole diameter
- At least 1x material thickness.
- Hole to bend
- 2.5x thickness plus the bend radius.
- Hole to edge
- At least 2x thickness.
- PEM hardware
- Match to sheet thickness + edge distance.
- Welds
- Leave access. Plan for distortion.
- Finish
- Call coating thickness on mating fits.
Why it matters
A radius tighter than the material allows cracks on the outside of the bend. Holes too close to a bend stretch into ovals. Hardware called for the wrong gauge won’t seat. Every one of these is cheaper to catch on the drawing than on the brake.
Sheet metal design questions
Plan on an inside bend radius of at least 1x material thickness. Stronger alloys like 6061 aluminum need more. A radius tighter than the material allows cracks on the outside of the bend.
Keep holes at least 2.5x material thickness plus the bend radius from the bend line, and at least 2x thickness from an edge. Any closer and holes stretch into ovals when the part is formed.
±0.005″ is standard on cut features. Expect about ±0.015″ on dimensions that cross a bend, since every bend adds variation. Call out tighter tolerances only where fit depends on them.
Send it anyway. Our engineers review every flat pattern, flag what drives cost, and tell you what a change would save before the job goes out for sourcing.
Keep going
More on how we source sheet metal parts.
