Broken Tap

[Pete G.]

Other than needing my head examined for even thinking about tapping a blind hole into the back of a lock bolster...but that's a subject for another day.

Now I have a tap broken in the bottom of a blind hole with no apparent way of getting it out. I suspect the tap may have cracked when it bottomed in the hole because it broke when I tried to back it out, so the hole is full of tap from one end to the other, with no part sticking out above the surface.
 
The only available gunsmith is only capable of taking parts out of a Remington and sometimes putting the new one back in; the only machine shop around only works on cylinder heads and the only welding shop hires guys who flunked out of welding school at the shipyard.

Is there a good way of tackling this, or would I be better off just ordering a replacement lock plate and starting over ?

[P.W.Berkuta]

I use blind holes for my lock bolt in the bolster all the time - the use of tapping fluid is very important in tapping this blind hole also proceeding slowly and cleaning often. Now that being said -- what kind of tap is it -- H.S.S. or carbon? Did the point of the tap make a mark on the outside of the plate? Is it possible to breakup the tap with a center punch and pick out the broken pieces? What size is the tapped hole (8-32, 10-32, or)? This is what I would try first: if the hole is tapped for a 8-32 and either a H.S.S. OR a carbon tap is in the hole I would get a small center punch and try to break up the tap and pick out the parts - this WILL take some time. If it does not come out I would look at the front of the lock and look for a dimple where the tap point has made a mark either during the tapping phase or when you beat on the tap to break it up. If no mark is visible then I would try to locate the point of the tap by measuring it's location on the back and transfer the measurements to the face of the lock. I would then drill a hole from the outside face of the lock using your tap drill. Then make the hole large enough to insert a small FLAT punch and hit the front of the tap to force the broken pieces back out the back of the bolster. If all the works I would then drill and tap for a 10-32 through hole in the lock plate. There are other suggestions but this is enough for now so you don't get "overload" -- good luck

[Acer Saccharum]

Is there a shop around you that does EDM? (Electrical Discharge MAchining) The tap could be burned out using EDM.

Some automotive shops have a tap burner.

[WadePatton]

two words: left-handed drills  (is that two?)

you may need to grind a divot to get it started, but the combo of frictional heat, vibrations, and Left Hand forces--just amazing sometimes.

[B.Habermehl]

Somebody mentioned using ferric chloride to loosen broken taps. Perhaps Jerry Huddleston? BJH

[Pennsylvania Dutchman]

As Acer said EDM would be the best choice. I've had a couple of taps burnt out with EDM over the years and it works very well. If you have access to a milling machine, you can cut the tap out with a carbide endmill.

[Mark Elliott]

I have a little tap removal set that consists of some special square carbide drills.   I bought it at MSC.   I have used it once or twice.   It worked as long as I was very careful about centering the drill.   I was using a drill press.   A milling machine would probably be better.   I never heard of EDM.   What does that cost to have a tap removed?   Another thought.  If it was a plain carbon tap, which I personally never use,  you could anneal the tap in the plate and drill it out.   

[billd]

Our local Vo-Tech school has a EDM.  Works great for removing taps.   Some local colleges have Adult Education classes in machine shop.  They may have a EDM too.

Bill

[Herb]

I have cut broken taps with a carbide dental burr.  Ask your dentist.  He probably has a drawer full of carbide burrs that won't cut teeth but will cut steel like butter.  Run it in a Dremel tool.

[PPatch]

You guys are amazing. Thank you for the info if I ever need it. And if I keep making guns, which I plan to, I will need it sooner or later. ALR is such a great resource.

dp

[chubby]

Is your tap a 3 or 4 flute tap? if it is a 4 then you can sometimes cut a slot in an allen wrench close to the hole size you may have to grind a little to make it round but the fingers will slide down between the wall and the flute of the tap moving it easy back and forth to remove it, if its 3 you may be able to break it up. there is a company that makes a set of 4 flute tap removers with the correct finger size but i cant think of who it is offhand? if you check with MSC or McMaster Car they have spiral taps that makes the chip come out of the hole in a spiral coil that is the type that i use on all of my blind holes, hope this info may help! best of luck Chubby

[pushboater]

I was facing this same situation a couple of months ago with a 3 flute 6-40 tap. Like Chubby said, I took a cut off wheel on my Dremel tool and used it to form three small fingers on the end of a small screwdriver. the three small fingers fit down between the tap and the wall of the hole. I was then able to back it out using downward pressure. It not only worked once, but it worked twice when I managed to break a second tap in the second blind hole I attempted. You'd think that I would have learned from the first mistake!

Capt. David

[Pete G.]

Thanks for all the suggestions. I find it enlightening that the first guy who answered says that he taps blind holes all the time, and seems to be very experienced in removing broken taps. I think there is a message there that I intend to remember.

Meanwhile, having always been a strong proponent of giving the easy way a chance to fail first, I procured a tap extractor. After applying this little gadget to the broken tap it backed right out. Having recovered from that mistake, it's on to the next. Seems that I spend more time in "recovery" mode than in the "build" mode.

[necchi]

Seems that I spend more time in "recovery" mode than in the "build" mode.

That's an important statement, I always learn more fixing mistakes than I do getting it right!
Don't get me wrong here, getting it right is a good thing, but I learn a lot from making a repair or fixing a mistake, 

[Mark Elliott]

You ONLY learn from mistakes.   You NEVER learn anything when you get it right.

[Acer Saccharum]

I don't agree with you on that, Mark.

A difficult job, well thought out and planned, if it comes off just right, is a great learning experience.

[Paddlefoot]

"The difference between an apprentice and a journeyman is that the journeyman knows how to fix his mistakes." 

[Robby]

Your never too old to learn. Its one of the great wonders of living, learning.
Robby

[Dphariss]

If you have a good drill press and a drill press vice a carbide drill or miniature center cutting endmill 3/32 perhaps will cut it right out almost like cutting mild steel.
These are not that expensive in the smaller sizes and can be purchased from MSC or other machine shop suppliers.
If properly undersized it will just leave pieces of the tap in the hole.
This will only work if the part is solidly positioned and the drill or mill is steady and the feed is consistent. If anything moves the carbide breaks. Loose parts of the tap need to be removed as you drill so blowing them out with air is a good idea or  they may jam and break the drill/mill. Buy 2-3 of the carbide when you buy them.

Dan

[P.W.Berkuta]

Thanks for all the suggestions. I find it enlightening that the first guy who answered says that he taps blind holes all the time, and seems to be very experienced in removing broken taps. I think there is a message there that I intend to remember.

Meanwhile, having always been a strong proponent of giving the easy way a chance to fail first, I procured a tap extractor. After applying this little gadget to the broken tap it backed right out. Having recovered from that mistake, it's on to the next. Seems that I spend more time in "recovery" mode than in the "build" mode.

Experience is gained by education and practice and this is true for all things. You learn the know how to drill & tap blind or through holes or remove broken taps with time and experience. If you do not learn proper metal working techniques then you must stick with something less complicated. I'm glad you got the tap out you have now learned what to do if it happened again and it will unless you never tap another hole .

[eddillon]

I have successfully tackled the same problem by carefully grinding out the center of the broken tap with a small burr in a Dremel tool.  A couple of whacks with a punch shattered the remaining part of the tap.  Turned the lock over and shook out the pieces.

[Dphariss]

Drop of acid, like nitric, in the hole may loosen the tap in a few minutes
 and allow it to be removed. A trick I had not thought of when making my first post.

[huntinguy]

from what I have seen, taps usually crack on the way out and break later. It is the chip that gets in behind the cutting edge that binds during reversal.

OIL, lots of quality cutting oil. Followed by a good bath of solvent, a fine paint brush to clean off the tap. If I do this every quarter turn I seldom break a tap. I would also seriously invest in a tap guide. Not a block, a guide. They look like a cross between a arbor press and a drill press. I don't have steady enough hands to use a block.

As for getting the tap out. I couldn't add any valuable advice. so, that said, there is always drill out the tap, weld up the hole, polish the weld and re tap. The is a last resort thing though.