What is the minimum bend radius for a pipe?

It depends on diameter, wall thickness and material. As a guide, about 2–3 times the outside diameter is easy, and about 1–1.5 times is possible with mandrel bending on suitable tubes.

Why does a bent tube flatten?

On the outside of the bend the wall stretches and on the inside it compresses, so the round section tends to become oval. A mandrel inside the tube and a larger radius reduce this.

Pipe or tube: what is the difference?

Pipes are sized by a nominal bore and schedule (wall thickness) and are used for fluids; tubes are sized by exact outside diameter and wall, and are used for structures and precise parts.

Pipe and tube bending job work: radius and limits

Pipe and tube bending forms straight pipes into bends and shapes for frames, handrails, exhausts, hydraulic lines and furniture. On a CNC rotary-draw bender the tube is clamped to a bending die and pulled around it, often over a mandrel that stops it collapsing.

Quick facts

Methods: Rotary-draw (with or without mandrel), roll bending, press bending
Materials: Mild steel, stainless steel, aluminium, copper tubes and pipes
Typical centre-line radius: About 1.5–3 times the tube diameter
Angle tolerance: About ±0.5–1°
Watch for: Ovality, wrinkling and wall thinning on tight bends
Usually priced: Per bend or per piece

How tight can a tube bend?

The tighter the bend and the thinner the wall, the more a tube flattens or wrinkles. A bend radius of about 2–3 times the outside diameter is easy; down to about 1–1.5 times needs a mandrel and the right dies. Bending shops quote the radius their dies give, so use their standard radii where you can.

Design tips

Keep a straight length between bends (about 1–2 times the diameter) for clamping
Use the same bend radius throughout a part
Give bends as angles and lengths between bends (or as a 3D model / XYZ points)
Mention ovality limits if fluid flow or fitting matters

What to send

Tube outside diameter, wall thickness and material
Bend radius, angles and straight lengths (or a STEP model)
End finishing: cut, flared, threaded, welded
Quantity and finish (polishing, plating, powder coating)

Need pipe and tube bending done?

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Questions

What is the minimum bend radius for a pipe?: It depends on diameter, wall thickness and material. As a guide, about 2–3 times the outside diameter is easy, and about 1–1.5 times is possible with mandrel bending on suitable tubes.
Why does a bent tube flatten?: On the outside of the bend the wall stretches and on the inside it compresses, so the round section tends to become oval. A mandrel inside the tube and a larger radius reduce this.
Pipe or tube: what is the difference?: Pipes are sized by a nominal bore and schedule (wall thickness) and are used for fluids; tubes are sized by exact outside diameter and wall, and are used for structures and precise parts.

The figures on this page are typical values for guidance, written by Diemeco from standard engineering practice. They are not a specification: confirm grades and properties with the relevant standard or the supplier's mill test certificate, and tolerances with your workshop. Last checked 15 October 2026.