Press Brake Bend Radius and Flange Design Checklist
This page is a standalone engineering guide for buyers and designers who need formed sheet metal parts to pass first-article review. It is not the main bending service page; it explains the bend radius, flange, hole placement and inspection details that should be checked before an RFQ.
Why This Checklist Exists
Press brake bending looks simple from the outside: flat sheet goes in, angled part comes out. The expensive part hides between those two moments. Material stretches, holes move, coatings add thickness, welds pull panels out of square, and tiny flanges can be impossible to hold without special tooling. A clear design checklist helps MSTFAB review the risk before production, not after your assembly team has a box of almost-right parts.
Trust Table for Buyers
| Buyer Concern | What We Check Before Quoting | Why It Matters |
|---|---|---|
| Will the bend crack? | Material grade, thickness and inside bend radius. | A radius that is too tight can split the outside of the bend, especially on harder alloys. |
| Will holes still line up? | Hole-to-bend distance and bend sequence. | Features too close to a bend line stretch or shift during forming. |
| Will the flange be makeable? | Minimum flange height against available tooling. | Short flanges may need tooling changes, reliefs or a design adjustment. |
| Will coating affect assembly? | Powder coat or plating allowance on threads, slots and mating faces. | Finishes add real thickness. Pretending they do not is how threads become decorative. |
Bend Radius: Start with Material Thickness
A practical starting point is to keep the inside bend radius at least equal to the material thickness. A 2 mm sheet usually wants about a 2 mm inside radius unless the drawing, tooling and material allow otherwise. Tighter bends are sometimes possible, but they should be a deliberate engineering choice, not a default CAD setting wearing a serious face.
Flange Height: Give the Tooling Room to Work
Very short flanges are a common reason a drawing gets sent back for revision. The press brake needs enough material for the punch and die to hold the part accurately. If the flange is too small, angle control becomes unstable or the tooling simply cannot reach the feature. For tight packages, send the 3D model early so the forming route can be reviewed before pricing.
Hole and Slot Placement
Keep holes away from bend lines whenever the function allows it. As a rule of thumb, start around 2-3 times material thickness from the bend area, then confirm with the supplier based on the alloy and bend radius. Holes sitting too close to a bend can become oval, shift position or create a weak edge. It is one of those small mistakes that looks harmless in CAD and rude in real life.
Check before RFQ
- Material grade and thickness
- Inside bend radius
- Minimum flange height
- Hole distance from bends
- Finish thickness and masking
Send with drawings
- STEP file and 2D drawing
- Critical-to-fit dimensions
- Required surface finish
- Annual volume and pilot quantity
- Inspection or FAI requirements
Related Service Page
For broader production capability, equipment and formed part examples, use the core sheet metal bending service page. This standalone article stays focused on design rules and buyer-side RFQ checks.
FAQ
What is the safest bend radius for sheet metal?
Start with an inside radius equal to material thickness, then adjust based on alloy, thickness, tooling and functional requirements.
Why do holes move after bending?
The material stretches around the bend zone. Holes placed too close to that area can shift, distort or become difficult to inspect reliably.
Should every bend dimension be tightly toleranced?
No. Tighten the features that affect assembly fit, loosen cosmetic or non-critical dimensions, and define inspection points clearly.
Need a Bend Review Before RFQ?
Send STEP, DWG or PDF drawings. MSTFAB can review bend feasibility, hole placement, finish allowance and inspection points before quoting.
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