Hello, I just thought I'd share a little experiment I've just done. I have made a crude rotary broach for use on my mill.

After making an 2 degree angled clamp fixture, and a crude 6 position indexer (an ordinary nut drilled out, with a set screw ), I made a 4mm hexagon shape with a 2 degree relief angle from a piece of 10mm drill rod. The other end is center drilled 4.5mm.

A second piece of the bar is made and drilled off-center, and a 4mm steel dowel pressed in. This part goes into the chuck on my mill, and engages the crude broach, to make it wobble.

I did not harden the broach as it was only going to be used as a test in aluminium.

I guess the pictures will explain it better!