In article ,
"Bob La Londe" wrote:

So what's the proscribed method? I expect I need a pretty consistent radius
bottom. What's the best way. Make a rough semi V lathe bit, and then make
a decent round one to finish?

Most o-ring grooves are square - there's little or no need to match the
profile of the ring, just get the size right so the ring compresses
adequately to work...

If you want a round bottom, and you are HSMing rather than production,
just use a round-nosed tool and take it easy, unless you've gone and
decided to work in stainless where you can't take an easy cut, in which
case you'll need a machine that will stand a real cut. Roughing out with
a V does not reduce the power needed to make the final cut at full
radius, and making the cut in any normal material is not likely to dull
the tool much.

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