Tuesday, January 11, 2022

Undercutting tool

I needed an undercutting tool for the part in the last post, so I made one from an old HSS end mill.

ER32 chuck loosely held in an ER40 collet, serving as a manual rotary/linear axis.  Grinding wheel in the mill spindle:

One of the features it cut:


  1. Hehe, nice! Our machinist once declined grinding with his CNC like that, because he said the rotational speed of the CNC spindle is to low for grinding. But it looks like it still works.

  2. Great idea for old carbide! May have to try this trick eventually. IIUC the bit was allowed to spin within the er32 chuck within the er40...? If that's the case, how did you ensure that the "lead" cutting edge (the one that would cut the flat in the final picture) was 90 degrees considering it was held by hand?

    Also, still liking that machine?

    1. Yep. The ER30 shank bottoms out on the machine table, so there was a hard stop that set the cutter width and squareness of the underside. I actually tilted the table a couple degrees off 90, so there's a tiny bit of relief behind the outer cutting edge.

      Still liking it. I have been noticing some calibration issues for >3 axis stuff though, which I'm working on measuring properly.