In the RCM thread "Making a micrometer stop for a Clausing lathe" in
July 2012, I talked about getting a pair of 35-degree (half angle)
conical mill bits (V-203 from Conical Tool Co). They came a while ago,
and I just today made my first trial cut on a block of scrap aluminum.

This works a treat. My first trial grooved block sits quite solidly and
stably on the 70-degree (included angle) V-way ridge of my Clausing 5914
lathe. It took me all of ten minutes to make the trial block.

I roughed a 5/16" slot first, before cutting the V groove.

As for the Conical V-203, it seems very well made, and the fit of the
shank into the Waldon holder is almost airtight. It certainly cuts very
well.

Joe Gwinn