[pprichard]

I need to cut 1.5" diameter round grooves to a depth of .275" into a 2.25" OD steel bar on either a manual lathe or mill. (See picture of old part that I need to remake!) Which machine would be better? I have seen somewhere that you can set a standard cutting tool on a lathe to rotate at a .75" radius and hand feed across the rotating round bar through the cut. Anyone have experience with this?

Another thought would be to set the bar to rotate on the mill bed and use a side cutter with the DRO to cut a radius into the side of the bar. This seems most likely as the best solution to me.....

Any suggestions on an alternate method?

[HuFlungDung]

How accurate does it have to be? If close were good enough, I would use a 3/4" round insert in a large toolholder, and plunge to depth right in the center of the groove. Then, work the tool sideways and keep checking the shape of the groove against a piece of 1.5" OD round stock. With a 3/8" radius tool, its broad curve makes it fairly easy to get nice broad overlaps between adjacent plunge cuts.

If you have a worm drive indexing head to hold the stock, and a 1.5" dia endmill, you would also get excellent results just plunging to depth (in the Y direction) and then clamping the spindle, and rotating the indexer one revolution via the hand crank.

[pprichard]

Thanks for the information. I think I can manage the setup on the lathe that you suggest.

Thanks!