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Yikes, now I've done it.

Tiny screw -- probably nickel-silver -- broke off inside a rotary valve stop arm as I was (over)tightening it.

Drill it out and retap? Is there a less destructive way?

Working on getting this 100 year old Kruspe string linkage 5/4-size BBb back in action... I'm close.

Look in the bottom, and see if it's drilled all the way through but only tapped part way down. If it's nickel silver, it should drill out easier than steel, and you might consider drilling it out from the bottom if you have a pilot hole there.

If it's worth it to you, take the damaged one and the undamaged one to a machine shop.

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bloke wrote: ↑Wed Sep 27, 2023 8:24 amIf it's worth it to you, take the damaged one and the undamaged one to a machine shop.

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You may need a drill press to get this right and not screw up the arm.

Sometimes you can get screws to come out with a left hand drill bit. Usually works best with slower speed and harder feed so it has a chance to bite into the screw and apply enough torque to back it out. I’ll practice on a scrap piece before trying on the actual part to see what it will take and if it won’t do it, go to plan “b”, drill it out and use a tap to get the threads clean or fish out the remains with a dental pick.

I really do need to get a bench motor.

Harbor Freight does have all sorts of bits, but I'm sort of agreeing with Dan Schultz (a comment that he made years ago) that most of them aren't worth crap. I'm having better luck finding affordable (good) bits on eBay. I am a cheapskate, but I like to pay low prices for really good quality. I'm one of those types of absurd-expectations cheapskates.

The left hand drill bit thing does work sometimes, but sure that you flipped it upside down to see if the pilot hole was drilled all the way through, because - in my opinion - that's the easiest way to get rid of a broken off screw in a stop arm.

Something else that's handy besides a bench motor (and I don't have a bench motor, but I think they're just fine) is an aluminum hand vice with a butterfly tension screw. It's nice to be able to hold something made of soft metal - such as brass - really securely without marking it up.

Just reminded myself that my ancient aluminum hand vice is busted, and I need to get another one, and I'm also remembering that I need to order a bunch of new bicycle gear shift cables - which I use to pull drilled dent balls through instruments. I use them until they get too ragged, and then toss them in the trash and buy more. I do have ways of extending their life, obviously.

Drilled through the bottom and got it out no trouble. Took it to my repair guy and he helped me retap and get a new screw in there, easy peasy.

arpthark wrote: ↑Sun Oct 08, 2023 5:49 pm Drilled through the bottom and got it out no trouble. Took it to my repair guy and he helped me retap and get a new screw in there, easy peasy.

OK...
Now, break off the NEW one, and drill it out from the top with a left-hand drill bit, and report back in regards to the comparative ease...

Sledge hammers should only be used on piccolos.

Probably 70% of the time, I can tease out broken off rotor center screws, finger buttons, and valve stems with a small screwdriver.

If I can't immediately push on a rough spot on the broken off tops and get them turning, sharpening a small screwdriver down to a knife blade and pounding it in to the broken off screw creates a slot that can be used to unscrew the broken off piece, and pounding on it also tends to loosen up the threads.

sidebar:
Nickel-brass screws seem to be the least likely to break. Brass screws and Chinese stainless steel screws seem more likely to break.