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Uman
10-11-2003, 10:09 AM
I need to bore a 1-17/64" thru hole in tubular Delrin plastic 6" deep. Any suggestions on a source for this drill bit?
Thanks in advance,
Jeff in Florida

darryl
10-11-2003, 01:32 PM
Why not try a spade bit (speed bit) for woodworking. They work well in plastics, have a shank that might just be long enough, especially at that diameter, where part of the chuck could enter the hole without interference, giving the full depth of hole. Use a 1 5/16, test the hole in some scrap, and grind some away from the sides of the bit to achieve the proper size. I doubt you'll find the size you're looking for unless you spend big bucks, and there's no guarantee that in plastic it'll drill the exact size hole anyway. The spade bits by comparison are throw away priced, and in my experience, work well, even in aluminum. If your workpiece is solid, it has meat to guide the point, if it's hollow, and needs enlarging, you'll have to bore it on a lathe with a long enough boring bar and sharp cutter. Most plastics will need a minimum depth of cut to remove material at an expected level. Too small and there could be no chips, too large and it digs in deeper than expected. Trial and error. Beware the fumes from machning that stuff.

Joel
10-11-2003, 02:05 PM
Under $40.00 at J&L. MSC will have them also.