How to setup your mandrel

When positioning a mandrel, it is important to use the front edge of the mandrel body/shank as the reference point. Many people make the mistake of using the articulating balls (where present), and this is incorrect.

The front edge of the mandrel body should be positioned just in front of the bending tangent point (often identified as the centreline position of the bend die).

The table below will give you an indication of an acceptable position in front of the tangent point, based on the outer diameter of the tube being processed.

Once positioned, any mandrel balls that are present should be checked to make sure that they have correct contact with the groove in the bend die, and are articulating freely.

The mandrel body and balls should be lubricated where possible prior to use, this reduces the amount of friction between the mandrel and the tube. Not only does lubrication improve performance, but it also increases the longevity of your tooling.


  • Force mandrel inside the tube if it will not fit easily.
  • Over clamp the tube onto the mandrel balls. The balls and linkages will break during bending.
  • Don’t use more balls or segments than are required to produce a bend.
Tube Outer Diameter (mm) Tangent Setting (mm) in front of tangent point.
6mm – 8mm 0.75
9mm – 12mm 2
13mm – 16mm 2.5
17mm – 19mm 3
20mm – 24mm 4
25mm – 29mm 5
30mm – 44mm 5.5
45mm – 53mm 6
54mm – 84mm 6.5
85mm – 117mm 8
118mm – 152mm 9