Tube Bend Radius Chart (Printable)

Minimum bend radius guidance for stainless instrument tubing: the conservative 3× OD working rule by tube size, published hand-bender die radii, and the wall-and-temper caveats that decide whether a bend is safe.

Bend radius by tube OD

Tube OD	Conservative minimum (≈3× OD)	Published die radius example	Note
6 mm	18 mm	15 mm (2.5× OD)	Most forgiving small size
8 mm	24 mm	24 mm (3× OD)	The 3× rule lands on the die
10 mm	30 mm	24 mm (2.4× OD)	Verify wall and temper under 3×
1/4 inch	19 mm	—	6 mm class tooling
3/8 inch	29 mm	—	Wall: 0.035 in bends easier than 0.049 in
1/2 inch	38 mm	—	Largest common hand-bender size

How to use this chart

Three times OD is a working minimum for annealed tube with a matched lever bender — a rule of thumb, not a guarantee. Published hand-bender dies run roughly 2.4–5× OD depending on size, so follow the bender manufacturer's limit for the exact tube. Heavier walls bend tighter than thin ones at the same OD; hard-drawn tube resists and springs back more than annealed — if the tube fights the bender, use softer tube or a larger radius, never more force.

From our guide: bending stainless tubing without kinking. State OD, wall and temper with the size list on theRFQ.