On Thu, 05 Apr 2012 00:43:42 -0500, Tim Wescott
wrote:

On Wed, 04 Apr 2012 22:09:13 -0700, Bob La Londe wrote:

If you needed to put a hemisperical end on a bunch of 1/4" stainless
dowels how would you tackle it? Say 400, give or take.

How exact?

If it didn't have to be too terribly precise, I'd figure out how to make
an end mill with a hemispherical "innie", 1/4" in diameter. Then I'd
push those dowels into it.

If that wouldn't cut it for fit or finish, I'd make a cutter with a
circular 1/4 turn, 1/4" diameter cutout, and individually turn each dowel.

Or, I'd make or obtain a spherical turning tool, and use that.

Or, I'd make a drawing, and give it to a company that has an NC lathe...

Back when people still knew how to use speed lathes with tool rests
(like the ones on woodworking lathes), freehand turning, there was a
common tool for that work.

It's a flat piece of HSS bar, maybe 1/8" or 3/16" thick, with a hole
drilled in one end, countersunk to leave a sharp, circular cutting
edge on the opposite side of the bar. The hole is somewhat smaller
than the diameter of the ball or hemisphere you're going to turn. I
don't know if there's a formula for the relative hole size. The
cutting edge just shaves a thin chip off of the ball as it develops.

If you want to test your skill, try it sometime. It's not for the
faint-hearted, and make sure your insurance is paid up. But it does
work once you get the hang of it. Make sure it has a long handle and
that the rest is set close to the work.

--
Ed Huntress