Poor mans CNC lathe cutting radius on manual lathe

[Frank S]

Quite by accident I made a convex cut on a part I was making way back when I was a teen and trying to teach myself how to run a lathe I had just bought. There was some object wedged between the head stock and the edge of the cross slide that I didn't notice as the cutter moved across the part the cut became less and less I had started out making a pretty deep cut in aluminum but before I had gone half way to the center my tool wasn't even touching. That was when I noticed the object. Haven't thought about purposefully duplicating the result until your thread Thanks