Hand drill chuck thread size (eggbeater)

[John Stankus]

I was poking around at two eggbeater drills my brother gave me a couple of years ago. I am having some trouble with the chucks. I am trying to figure out the thread size so I can get a tap and die and clean up the threads. I also would like to take the chuck apart to clean up but I cant seem to get the parts to budge.
No markings left other than made in USA on the back of the big gear.

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The diameter of the the threaded part on the one I measured was about 0.3115" and the threads seemed to match up to the pitch of a 10-24 screw. I am guessing it is a 5/16-24 thread. Are these UNF threads (National Fine) or some other obscure thread like the Stanley plane threads?

Thanks

John

[Bill Houghton]

5/16" - 24 is, indeed, National Fine Thread. Stop by your local hardware store and see if they've got a thread measuring board, or a selection of nuts, that includes 5/16" - 24. If that's what you've got, you're a lucky ducky.

If you're going to do much machine maintenance, a tap and die set is worth owning. Otherwise, if you've got a bench grinder, get a Grade 8 bolt that size (assuming it is, indeed, 5/16"), and grind off a taper at the end, to make a shaving edge on some of the threads. Lubricate and be careful. For the male threads, try a steel wire brush and vigorous brushing.

To take the chuck apart, clamp the body in a metalworking vise (ideally, find something to wrap it in that will allow good clamping but no damage) and unscrew the bottom. Be careful: there'll probably be three jaws and three springs. The springs will want to escape, and replacements aren't easy to find. Best, once you get the bottom loose but not off, to put the whole thing in a large, clean container - say a five-gallon bucket - and take it apart inside that. If parts fly out, they'll probably stay in the bucket. Reassemble in the bucket, too.

[John Stankus]

5/16-24 is my estimate of the what it is. I was assuming NF but wanted to see if anyone knew for sure the actual thread size if it was a standard on these things. I know Stanley did some oddball rolled threads on their planes.

I have a good metric tap and die set and a small SAE (only up to 1/4-20) so I guess I need to go get a die.


John

[Bill Houghton]

Are the threads munged up? Or just rusty and dirty? Try strenuous wire brushing first.