Broken Tap

[Tizzy]

OK, how many of you have ever broken the tap off in the bolster? More importantly, how did you fix it? Not that I just did that or anything....... 

[westerner]

I'd make a new one.   No lathe?  I'd still make a new one.     Also is a good excuse to change to patent breech. 


                Joe.   

[Tizzy]

Sorry Joe, I should have been more specific. I broke the tap off in the lock bolster while threading for the lock bolt.

[ehoff]

Been there done that.

If its a carbon steel tap you can beak it with a center punch.

If it was HSS then its harder,  you can try to use a small punch to try to turn the tap. If you can find a " tap remover" you can try one, but I've never had much success with them. They have "fingers" that fit into the flutes and then using a wrench try to turn the tap out.  Check with local machine shops to see if they have a "tap zapper". The last thing that might work would be to drill a series of small holes around the hole, then cut around it with a jewelers saw, then have someone weld up the hole.  Sure you will get some other suggestions.

[David Rase]

Never broke one off in a bolster but broke one off in a tumbler several months ago.  Ground it out with a dremel and a diamond tipped burr.  I was going to have it welded up but was able to acquire a replacement from guess who, The Riffle Shoppe. 
I have never seen anyone have success with a tap extractor.  Save your money.  If I ever snap off another tap I will have a shop EDM it out.
DMR

[Dphariss]

Been there done that.

If its a carbon steel tap you can beak it with a center punch.

If it was HSS then its harder,  you can try to use a small punch to try to turn the tap. If you can find a " tap remover" you can try one, but I've never had much success with them. They have "fingers" that fit into the flutes and then using a wrench try to turn the tap out.  Check with local machine shops to see if they have a "tap zapper". The last thing that might work would be to drill a series of small holes around the hole, then cut around it with a jewelers saw, then have someone weld up the hole.  Sure you will get some other suggestions.

A drop of nitric acid and a drop of water will often eat the high carbon steel in the tap faster than the part. This will loosen it an perhaps allow removal.
If you have a good drill press with  a vise a carbide drill or small center cutting carbide end mill like a 1/8" or so will cut it right out. But carbide is brittle and you need a lot of speed, slow feed and the part anchored firmly for this to work well. But it is the fastest and easiest. Once its had a mill or drill run through it it will break out easily or fall out on its own.

This is better than anything else I ever used through hole or blind hole it works and does not damage the hole.

Some castings have hard spots and annealing is a good idea.

Dan

[chuck-ia]

Yes, broke one a couple years ago, it was only in a couple threads maybe 3 when it broke. I tried everything I could think of. Finally just drove it back out and retapped. Turned out ok. Next time I will use a small die grinder and small tip to grind the tap out. chuck

[BJH]

I have gotten them out with a combination of methods. With carbon steel taps you can heat the part, tap an all cherry red, allow to cool in ashes, vermiculite etc to anneal the tap. Repeat as necessary til the tap is drillable. Or back out-destroy the tap with a punch. With a high speed steel tap all bets are off. With their different steel chemistry they will not respond to my annealing technique. Most times it is better to redrill and tap to a larger size such as 10-32 if the origional hole was meant to be 8-32 after removing the broken tap. I now have acess to a local machine shop with a EDM machine for disasters with taps that have to be perfectly removed.

[BJH]

P.S. Since this is the rear lock bolt, having a bolt one size bigger is a benifit, this will prevent broken frizzen springs because of accidently switched bolts. That is if, the lock is a flint lock.

[oldiemkr]

If there are any machine shops in your area ask them where they get taps burnt out {EDM}. Believe me they have done it before and they might help. If the hole is thru and not blind you may get it out with an extractor but the odds are not good.

Grinding down into the tap drill hole can distort the hole so you may need to go oversize anyhow. Try a thin cutoff type wheel in the dremel first. Cut an X into the part sticking out and you may be able to crack it with a small punch and get it out.

Use safety glasses!!!

[Tizzy]

Thanks for all the replies, lets me know I'm not alone in having this blunder. Besides having the tap break, I am lucky in many things. First, I'm thankful for all you guys help. Second, the tap was a carbon steel tap so it can be annealed. Finally, it was a 8-32 so I can upgrade to the 10-32 which honestly I should have done in the first place.
Last night in a moment of haste I attempted to get the tap out with a punch before annealing it. The result, a  broken punch point. My my failed effort distorted the hole slightly, but this morning I verified that a # 21 drill for the 10-32 would expand the hole past the distortion, so I can continue with my repair attempt. For my second attempt, I think I will head you gentlemans advice with some annealing + a carbide drill and a little more punch action is in order. I hope I don't distort the hole anymore, but hey, in this day and age of interchangeable parts at worst I'll just have to purchase a new lock plate from Mr. Chambers. That fact got the mouse running on the wheel in my mind last night, and opens up a new topic. My minor set back frustrates me. What would the original gunsmiths have done? The thought of laboring for hours at the forge and filling vice to complete the lock only to have a tap break of in the lock bolster would have been enough to drive a man mad. It's not like they could just mail order another lock plate that will closely match the inlet. It would be back to the forge. Time lost making another lock truly was money lost back then, and if it were the apprentice that broke the tap off..................

[David Veith]

If you have a mill and a good junk endmill. I can't think of the type you can cut them out.
David

[Acer Saccharum]

a good junk endmill.

In other words, a good endmill? That's all I have, used but good endmills.

I think you'll need a solid carbide 5/32 endmill to even touch HSS. Good luck.

I think the EDM tap burner is the best once you've determined you can't back out the broken tap.

Tap extractors are a waste of money.

EDM it out before you resort to bashing it out. I know, I have bashed them out, and I wish'd I hadn't.

[Jim Kibler]

Not that this will help with your current situation, but there's nothing better than a good quality two flute spiral point tap.  There's no comparison between them and a typical four flute tap.  Much less chance of breaking one off.

[KentSmith]

Done it before.  Tried a lot of different approaches but Jerry Huddleston once suggested the nitric acid approach on this board several years ago.  Tried that and bingo - the way to go if you have some nitric acid that is.

[Tizzy]

Kent, I don't have any nitric acid on hand. I do however have some of your Aqua Fortis I bought from you at the Southern Rifle Show last year. I doubt that would still be active enough though. Stain however does work like a charm. The rifle I'm attempting to button the lock up on has one of your hand forged butplates. That steel was a pleasure to work with.

[Rootsy]

A sinker EDM specifically is what is needed.  Also, if one ever runs into a case where you need to tap hardened material, a sinker can burn threads into the piece.

[westerner]

Oh! That kind of bolster. Me duh!

Okay, I'd cut that part of the bolster out. Slap a couple copper plates on and fill with weld. File it back to shape and start over with another tap.

             Joe.   

[Birddog6]

I have broken one the same way, on 2 dif occasions.    I guess I was not sure exactly how I did it, so I did it again just to be sure....    Both of them I worked back out with it with a pin punch under a lighted magnifier (one of them on a desktop & arm).  Can be frustrating as it seems like it takes forever to get it to back up past that first chip.  But once it does you are good to go. The key is having a good punch, which it seems you cannot buy anymore.
Now if it is sticking thru the other side you can get needlenose & carefully work it back & forth & loosen it.  Or if you have some sticking up, you can take a abrasive blade & cut a screwdriver slot in it & work it that way, BUT it is very brittle, so great care must be used. I put Kroil on mine while working them for a lubricant.

Went to using the spiral 2 flute taps with the turned down shanks, have not broken one in several years since I started using them. I buy them from MSC.

Keith Lisle

[keweenaw]

Carbon steel taps will shatter with the center punch.  Takes a good center punch and it will ruin the point on the punch but you can regrind that.  On cleaning up the threads in the bolster - there are lots of threads in there if you're going to  drill through, makes no practical difference if the first couple have some dings in them. 

Tom

[Dphariss]

Quality taps are a great preventer of broken tap syndrome.
Buy GOOD name brand taps from MSC or other quality supplier. Coatings help a LOT. Hardware Hank etc is a poor place to buy taps.
I have tapped quite a few 8x32 blind holes in 303-304 stainless, thousand maybe? Never kept track.
I think I have only broken one or 2 taps. But I am CAREFUL.
But I use taps ground for stainless with the TiN or TICN coating. They now run about 13 bucks each for Greenfield.

They will tap carbon steel too. They recommend oxide as the best for ferrous metals though.
Good taps are not cheap but when  all the work is done on a part and youa re tapping the last hole a broken taps is a real PITA and make scrap the part.
I still have a few old ACE taps around and I use them, carefully.
While ordering taps order some Castrol Moly-Dee Tapping Fluid. I bought a pint years ago and it is not empty yet. Only needs a drop of two on a small tap.
OR use Break Free CLP from you can get this at most places that sell shooting supplies. This solved some tapping problems at Shiloh once upon a time.
Tap Magic is pretty good too.
Good lube helps a lot.
Larger taps like 5/8 and 3/4 are harder to break.
Dan

[Nate McKenzie]

If its a commercially available lock, how about ordering a new lockplate?

[Millman48]

You might try one of these jewels.  Got the broken tap extractor from Brownells, and it worked very well for me.

[T*O*F]

Having been in the automotive business for 30 years and encountering this problem a plethora of times, I never had one I couldn't remove.  You must first understand that it is the cutting chips which lock your tap in place.  Once removed, they can usually be easily backed out.

The nitric acid dissolves the chips rather than the tap.  If you give the hole a good solvent wash, followed by compressed air, you can usually clear the chips.  Then anneal the tap.  They always break at a slight angle which leaves a shoulder.  I make a small chisel from drill rod, find a part of the tap which will provide a purchase for the chisel, and gradually tap it out.  Use plenty of lube.

Also, if you know someone who is a whiz with a smoke wrench, you can usually blow the tap out because it is a dissimilar metal than the lockplate.  If you want to punch the tap out, you must do that while the tap is still hard, otherwise you will just peen in into the hole.

[Tizzy]

Thanks everyone for the good advice. I am thankful for the help. I've located a machine shop near my house and talked to an employee there. I explained the situation and he is willing to help. Don't want anyone to think your advice was in vain, it is all great knowledge, it's just I think I'll let the machinist take a shot at it as I don't want to risk buggering up the lock plate. Thanks again.