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Tube and fluid parts

Tube Assemblies: Bent and Coiled Tube, Built to Drawing

A tube assembly is more than a bent tube. It is a tube that has been bent or coiled to a defined path, has an end form that has to seal or connect, and often carries a bracket, a ferrule or a sleeve that has to sit in a fixed relationship to the bends. The drawing decides which of those operations are ours.

What decides the assembly

Three things govern whether a tube assembly can be built as drawn: the bend radii against the tube diameter and wall, the length of straight between bends, and the end form – a flare, a bead, a ferrule or a brazed joint. Bending is done on CNC mandrel benders so the bend sequence repeats; the tube itself may be drawn or coiled in-house, and the joints are confirmed against the drawing before a fixture is built.

What we make in this family

  • Bent tube to a defined path – CNC mandrel bending, including multi-plane bends, with the bend sequence set from the drawing. See tube bending services.
  • Coiled and helical tube – tube wound to a stated coil diameter, pitch and number of turns, with controlled ends. See tube coiling.
  • Sub-assemblies – tube plus the brackets, sleeves or end pieces that belong with it, assembled and checked as one item. See assembly and sub-assembly.
  • Brazed joints – where the drawing calls for a joined tube assembly rather than a single bent piece. See brazing.

What the drawing has to say

  • Tube material and wall. Wall thickness sets the minimum bend radius; the thinner the wall, the larger the radius or the more support the mandrel needs.
  • Bend radii and the straight length between them. A mandrel needs straight tube to grip on either side of a bend. Two bends that meet immediately below that length cannot be formed in that order.
  • The end form. Flared, beaded, swaged, threaded or prepared for brazing – each needs its own tooling step, and several need a fixture to hold the datum while the end is formed.
  • The datum for the end positions. Where an assembly has to land in a fixed place, the drawing should say which end is the datum and what the tolerance is from it.
  • Whether the part is an assembly or a single piece. If it is joined, say so, and say how: brazing, welding or a mechanical joint.

Worked examples from the case archive

Related capability pages

Written by the Balford technical team, Zhuji, Zhejiang. Last updated 8 October 2026.

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Send the drawing with the bend radii, the straight lengths between bends, the end form and the material – we check the bend sequence and the tooling against it before quoting.

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Written by the Balford technical team, Zhuji, Zhejiang. Last updated 8 October 2026.