Work holding

Looks good for thick short material, but i can see thin material flexing and vibrating when not full supported in the middle.

Jonalm is right. This kind of clamping I would only use with downcut or diamond endmills.

The problem with more common upcut endmills is, that there is a force pulling the Z axis down towards machine table. If everything is fixed in a way that there are no vibrations, it is fine. But with vibrations it can happen, that the cutter pulls the material and it moves upwards and stops the cut for a moment. This little moment of not cutting results in a bigger force to be needed to start the cutting phase again. And this bigger force might be enough to pull down the Z axis and ram the spindle into your machine table.
(Of course I went through this experience)

What does a diamond or a downcut mean:
* Diamond end mills have no spiral which puts a directed force in Z direction. It's pattern means that in average there are as much up as down forces. The effective force is in direction of the tools rotation. Because of the diamond pattern there is no risk in get stuck.
* A downcut has the same forces as the upcut but in the other direction. So, if you run into the situation explained above, the downcut endmill won't pull the Z axis into your machine table, but push it upwards. The work-piece might have ugly traces of this accident, but your machine table is not harmed.

Hi all,
Thanks for your response.
Never had a problem with thin materials though. Have used the clamps with thin balsa. Yes there is some deflection - you have to be sensible about distance between clamps - but finish is not affected - its wood after all!

The biggest advantage is not having to keep replacing sacrificial materials & being able to clamp materials with no surface marking.

Stuart