August 10, 2021

Unison Blog – The benefit of quality tooling

Tooling is an integral part of successful tube bending.

Quality tooling is a major investment and can often, over time, exceed the cost of the machine.

In this blog we look at the clamp and the pressure die. For more information on our tooling solutions, head here.


The clamp die grips the tube to the clamp section of the bend former so that the tube can be drawn through the machine as the bend former rotates with the bend arm.

The two clamps should be parallel to ensure maximum grip and be equal in length and have the same grip finish.

The clamp length is determined by the tube size, the tube diameter, the material, the CLR (Centre Line Radius) and the quality of the final product finish. Typical application require a clamp of 2 x Diameter in length.

If the clamp length is too short the lack of surface area contacting the tube may not be enough causing it to slip whilst bending causing lots of issues including wrinkling, so is the first thing to get right.

If is it necessary to have a short clamp length, then by shot blasting, serrating, diamond cutting the clamp and the former clamp section, it is possible to reduce it considerably; however, this will potentially mark or indent the tube.

Pressure Die

The pressure die holds the tube against the Bend Former and runs tangentially to the tool during the bending process as the former and clamp rotate around the centreline.

With the pressure applied by the bending machine at the line of tangency during the bending process, it creates a point of bend. 

Originally, the pressure die was a static die block that once clamped into position at the line of tangency did not move forward during the bending process. 

This, of course, created considerable drag on the tube at the point of bend, which being in a plastic state, caused excessive flattening and wall thinning on the outside of the bend. 

Subsequently the pressure die was attached to a follower axis to follow or push material into the bend.

Normally the pressure die finish is smooth, but occasionally it can be beneficial to add a coating or lightly serrate to push more material into the bend.

Modern machines allow the operator to control the speed and force by which the Follower Die moves in the relationship the Bend Arm, meaning the operator can optimise the flow of material on the outside of the bend and reduce wall thinning.

Check out our tube bending solutions here.

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