On Mon, 07 Mar 2005 23:34:15 +0000, Joe wrote:

He may need to control the feed rate to improve the surace finish...
Plastics tend to either "gall" or melt if fed too fast or slow... Then
again, don't they put liners in the drilled holes anyhow?

Regards,
Joe Agro, Jr.

No liners on cheap bowling balls. After drilling, the holes are sanded
smooth, and the edges beveled. The tool for that is basically a die
grinder with a long mandrel. A piece of sandpaper, shaped kind of like a
figure-8, held to the end of the mandrel with a screw.

When I was in college (when dinosaurs roamed the earth ;-), I worked in
the sporting goods department at K-Mart (discount stores chain). I
drilled the bowling balls. I learned all I know in a 1 hour session with
the factory rep. I used a normal drill press with a special jig to hold
the ball. The jig had X and Y feeds (manual) like a mill table, but the
feed was pretty coarse. I marked out the the ball with a grease pencil
and a strange looking, curved triangle thingy with a couple of arms added
to it. Lined up the center of the ball (marked at the factory by a dot in
a circle) with the drill spindle by eye using a pointed rod. Locked the
ball down, then cranked over to hole marks, changed to the proper drill,
and drilled the hole. Repeat for the other two holes, then sand with the
tool mentioned above. The customer's name or initials where stamped in
with standard steel stamps.

The pro shops have nicer equipment, and don't necessarily drill exactly
the same way I outlined above. The ones I've seen do use a drill
press, not a mill. They know how to drill balls for special gripping
styles, and they know a whole lot more about properly fitting a ball.

I don't think a mill is necessary for drilling bowling balls, but it
wouldn't hurt. The only downside is that mill table feeds tend to be
fine, which means a lot of cranking. It would be cool to CNC the mill,
and do the whole job automagically. One could do some neat engraving on
the ball with a small cutter.

-Ron