Precise Cutting of Heavy Brass Tube


I had a need to make bearings out of a brass tube and each piece had to be within a thousandth of spec. I had a brainstorm to use my ShopBot CNC as a measuring device and came up with this contraption.


The rod is 1/2" diameter with a 1/4" inside diameter.

The multitool is level and square to the machine and locked to a piece of 2x4 by landscaping tape and hot glue. Not exactly a permanent fixture but good enough for the job.

To actually cut the rod, I used the keyboard function, "D" set at 0.001" and set the zero position within 0.02" of the multitool blade. Then I just arrow keyed the tube into the rod with the RPM's at 6,000. The wire runs up the tube a short distance and catches the rings as they separate.

To repeat, I move Y to zero, zero Z and lowered the Z to the desired depth for the next cut.

I made a couple of test cuts to calculate kerf and see how good the cut quality was and then subsequent cuts were good. I needed 12 at 0.250" and 4 at 0.500".

After cutting, I cleaned them up with a disk sander and they were ready to use.

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