How would you machine this?

[Jeff Pahl]

Originally Posted by maclaren

The biggest problem with this machining task is that you will be turning a ridged piece of box tubing into a not as ridged piece of channel. So in order to compensate for the material that you are removing you will need to make a couple of blocks that you can slide inside the tubing so that you have something to clamp down to so that the tubing does not deform under the clamping pressure. If the sides of the tubing bend in under the clamping pressure that would cause the .75" slot the you mill to become wider once you release the clamping pressure.

We did something similar to this last year, on a shorter piece. The tubing will not want to stay rigid and hold the exact slot width that you machine. If you need the slot to be very close to 0.75, make sure to take more than one pass with a smaller bit so you can compensate for the spring effect. It may spring in or out, but be assured that if you take a single pass with a 0.750 mill, you will not end up with a 0.750 slot after you take the support blocks out. Otherwise, if you can leave the support blocks in the ends, that will help hold the tubing in it's original position.