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Sheet Metal Minimum Bend Radius by Material (Searchable Chart)

This chart lists the typical minimum inside bend radius for common sheet metal materials, expressed as a multiple of material thickness. Use it while designing parts or reviewing a drawing so the radius you call out will not crack on the press brake.

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Material	Condition / temper	Typical min radius (x thickness)	Conservative radius (x thickness)	Fabrication note
Cold rolled steel 1008/1010	Annealed / commercial	0.5	1	Forgiving in both grain directions
Hot rolled pickled steel A1011	As rolled	1	1.5	Scale and edge condition drive cracking
Structural steel A36 plate	As rolled	1.5	2	Heavier gauges need larger radius
HSLA steel 50 ksi	As rolled	1.5	2.5	More springback than mild steel
Galvanized steel G90	Coated	1	1.5	Coating can flake on a tight bend
Stainless 304	Annealed	1	1.5	Work hardens, expect high springback
Stainless 316	Annealed	1	1.5	Slightly higher forming load than 304
Stainless 430	Annealed	1	2	Ferritic, less ductile than 304
Aluminum 1100	O	0.5	1	Very soft, marks easily
Aluminum 3003	O	0.5	1	Good formability
Aluminum 3003	H14	1	1.5	Common for enclosures and trim
Aluminum 5052	H32	1	1.5	Common general fabrication alloy
Aluminum 5052	H34	1.5	2	Less ductile than H32
Aluminum 6061	O	1	1.5	Anneal before forming if radius is tight
Aluminum 6061	T6	3	4	Prone to cracking on the outside of the bend
Copper C110	Soft / annealed	0.5	1	Forms easily, springback is low
Brass C260	Half hard	1	1.5	Bend across the grain where possible
Titanium Grade 2	Annealed	2.5	3	Often formed warm, consult supplier

Values are typical shop starting points for a 90 degree air bend, not material specifications. Bend perpendicular to rolling direction when radius is tight, and confirm with your material supplier or a test bend before releasing production.

Bring bend data into your ERP routings

Optional: a short review of how to carry material, radius and tooling into your routing data.

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How to use the chart

Search for your alloy and temper, then multiply the typical or conservative ratio by the sheet thickness. A 2.0 mm 5052-H32 part with a conservative ratio of 1.5 gives a minimum inside radius of 3.0 mm. Use the typical value when you have a proven process and the part is not critical, and the conservative value for first articles, thick gauges, or any material with unknown mill history.

Match alloy and temper exactly, T6 and O behave very differently.
Use the conservative column when grain direction is not controlled.
Round the final radius up to the nearest punch nose radius your shop owns.

What drives cracking

Cracks appear on the outside of the bend where the material is stretched. The risk rises with harder tempers, thicker material, bend lines parallel to the rolling direction, rough sheared or laser cut edges, and cold temperatures. Heat treatable alloys such as 6061-T6 are the classic problem, which is why the table asks for several times thickness. Annealing, bending across the grain, deburring the edge in the bend zone, or switching to 5052 all lower the risk.

Radius and the tooling you actually have

In air bending the inside radius is formed by the V opening, not the punch nose, at roughly 15 to 17 percent of the V width. A punch nose radius smaller than that does not change the radius, but a larger nose radius will. Always check that the radius on the drawing can be made with the dies on the floor, and carry that radius into the flat pattern and the bend allowance so the part comes out on size.

Common mistakes

Designers often default every bend to a single radius, such as 1 mm, regardless of material. That works for 1 mm cold rolled steel and fails on 3 mm 6061-T6. Another mistake is quoting the radius without the temper, leaving the shop to guess. Put material, temper, thickness and inside radius on the drawing and use one radius per part where you can, because every distinct radius is another tool change.

Frequently Asked Questions

Is a bend radius of zero possible in sheet metal?

Only with bottoming or coining on soft, thin material, and it usually leaves a visible mark and risks cracking. Most shops treat a radius of about one times thickness as a practical floor for steel and soft aluminum, and avoid sharp bends on harder tempers.

Does bend radius depend on grain direction?

Yes. Bending parallel to the rolling direction is the weak orientation and needs a larger radius. When a tight radius is unavoidable, orient the flat pattern on the sheet so bends run across the grain, and note this on the nesting instructions.

Are these values the same as the material standard?

No. These are practical shop guidelines for air bending at 90 degrees. Mill certificates and standards define chemistry and mechanical properties, not guaranteed bend radii. Always confirm with a test bend on the actual lot.

What is the inside versus outside radius?

The inside radius is the tight curve on the concave side of the bend and is what drawings call out. The outside radius equals the inside radius plus material thickness, and is where cracking tends to show.

If your ERP routing and engineering data do not carry bend radius and tooling, we can help surface that data to your planners. Ask us how.

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