Author Topic: Re: WTB .4764 jobber Drill Bit (Read 479 times)

Frank46 · « **on:** May 11, 2012, 05:07:11 PM »

Check enco, msc or any of the machine shop supply houses. You may have to drill first and then ream the hole to the desired dimensions. Frank

Doc Brown. · « **Reply #1 on:** May 15, 2012, 03:50:57 PM »

Enco only has small ones. About 4 inches of flutes. I guess I could weld a rod on it. I wanted to use the .7344 and then a .75 reamer. Thanks.

GGaskill · « **Reply #2 on:** May 16, 2012, 09:07:50 PM »

I wanted to use the .4764 and then a .75 reamer.

Something is wrong with your numbers here. A reamed .75" hole (3/4") should have a pilot hole of about .719" (23/32"). There are 12" long drills with 9" of flutes available as off the shelf pieces.

If you can give us some idea of what you are trying to do, maybe we can give some suggestions.

Doc Brown. · « **Reply #3 on:** May 17, 2012, 07:22:30 PM »

Yes I have been typing in the wrong numbers here. Brain glitch. I need a .7344 just under so I can run a reamer through a bore. Thanks. I cant find anything 16 inches long anywhere. I might buy a gun drill. Could I get 1 gun drill. Just for a pilot then run jobber bits then reamer or do you have to do all the drilling with a gun drill. Thanks.

GGaskill · « **Reply #4 on:** May 17, 2012, 09:11:06 PM »

If you get a gun drill, be prepared to get a bunch of other stuff at the same time, including a high pressure oil pump. You will also need to modify your lathe to feed at a few machinist's tenths (.0001") per revolution so the oil pressure can force the chips out of the hole.

Something you might also consider is to drill at .750" and ream the next standard size larger. That way you could use .75" shot, although I suppose there are still round ball moulds that would fit a .750" bore.

Victor3 · « **Reply #5 on:** May 18, 2012, 01:26:27 AM »

Quote from: GGaskill on May 17, 2012, 09:11:06 PM

...I suppose there are still round ball moulds that would fit a .750" bore.

Lyman sells a .735 mould.

If going with that, I'd just use a 3/4" drill and no ream. The bore could be finished with a simple hone (sandpaper and a dowel) if the finish came out rough.