bond tiny bushing

I've got an egg shaped hole in the lock frame on my 1919 BMG...

This part is hardened 4140 and its hard to get into the deep hole anyway so welding it shut and remachining don't look like a good option.

So is there a good way to bond a bushing with a 0.187" OD by 0.150" high into a bore? What would you use? FWIW, if I tried a press fit, it would just break the part.

Karl

Reply to
Karl Townsend
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I think I'd try silver braze.

Pete Keillor

Reply to
Pete Keillor

Den 02-04-2012 13:46, Karl Townsend skrev:

Loctite 638?

Reply to
Uffe Bærentsen

Can you post a picture or a diagram?

Reply to
Tom Gardner

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in the botton pic, you can see a large diameter hole that soes to small diameter down in there. its egg shaped on mine. lets the trigger sit crooked.

karl

Reply to
Karl Townsend

nope

Reply to
Karl Townsend

If it has to be really hard, your options are limited. 4140 tempers over a wide range -- 400 deg. F to 1200 deg. F, with the lower temperatures producing the hardest result, of course. So silver brazing isn't an option unless you can tolerate lower hardness.

Epoxies will give you strength, say, "X". Soft solder, then, is around

2X. Silver braze will be 4X - 12X.

Consider a silver-containing soft solder (maybe 3X or possibly 4X). Some will melt nearer the low tempering range for 4140.

Reply to
Ed Huntress

How about a light press fit and lock it in place with LocTite sleeve and bushing locker. Loc-Tite green if I recall correctly.

Reply to
Bob La Londe

I second that. This would be the stuff to use for loose fitting cylindrical parts with gaps up to .010". For gaps up to 0.015" use loctite 680.

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McMaster has both.

Reply to
anorton

For reference, shear strength of Loctite Green (cured for 24 hours):

3,600 psi. Epoxy, 3,500 - 5,000 psi, depending on type. Soft solder (60/40 tin/lead): 6,000 psi. silver-bearing soft solder: 10,000 - 14,000 psi.

Silver braze is very hard to nail down because of some issues with thickness of joint, wetting, etc. It can range as high as 125,000 psi

-- much more than its bulk strength. (Don't ask me how that works; I've never gotten a good answer.) Typical shear strength in practice is 25,000 psi.

Reply to
Ed Huntress

It sounds like high shear strength is not an issue during use, although it may be during assembly if the idea is to hammer a press-fit pin into this bushing. Even then, I have tried to disassemble parts bonded with loctite

603 by pressing and hammering (almost up to the point of damaging the metal) with no luck whatsoever. The only thing that works is high temperatures.
Reply to
anorton

How about reaming it out so it is round. Then press in a hardened piece of steel then bore that to the correct diameter? To ensure the insert cannot come out some loctite bearing retainer would do the trick.

Reply to
Steve W.

No one else recommended this: rivet the hole closed, with soft iron, or bronze or silver. Then drill your hole in that. I'm not sure how much sidewall you'll get, of course.

Reply to
whit3rd

Call "Red Jacket" and ask them. Maybe they will ask you on the show!

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Reply to
Tom Gardner

Buy a new one, they WERE fairly cheap. Ohio Ordnance was one source. And what you have depends on the vintage. Some were cast, some(prewar) were machined from forgings and a bunch were made from welded-up stampings. This is a key part of the gun, don't cheap out. It directly controls the timing. If you want to mess with it after you get another, go to it. My experience with them has been that they were harder than hell and I didn't want to have to do anything more with them than I had to to get a legal semi-auto out of the parts kit. I don't think mine were through-hardened, I think they were case- hardened or nitrided. Mess with that sort of thing via welding or silver-brazing and you might get other problems later.

OK, see:

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Stan

Reply to
Stanley Schaefer

Drill and tap most of the way through then drive a screw into the tapped hole until it jams, cut off it's head and file flush.....finally, machine a hole down the center of it to suit your pin.

Reply to
PrecisionmachinisT

Damn, that's a good idea. I'll do it that way.

Karl

Reply to
Karl Townsend

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