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Old 04-19-2013, 04:29 PM   #1
Half Fast OP
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Broken tap or drill bit

When drilling or tapping a hole, what are the options for removing a broken drill bit or broken tap that is stuck in the hole?

I just finished a project that involved lots of new threaded fasteners and each time I held my breath thinking "Man, if I break this tap/bit I'm screwed". All went well but what to do if the worst happens?
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Old 04-19-2013, 04:31 PM   #2
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An EDM (electrical discharge machining) machine is usually the best tool for the job.
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Old 04-19-2013, 06:50 PM   #3
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That's what I was thinking. I was curious to ask if there were any other options but EDM was all I could think of.

Thanks.
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Old 04-19-2013, 06:55 PM   #4
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It's a PITA for sure, EDM is ideal solution but generally out of the reach of backyard or home workshop types.

A former colleague always had reasonable success by tapping around radially with a punch if anything was sticking out, but the punch usually gets pretty chewed up.

Another guy that worked with me showed me a trick when we had a tap break off in a mold that was in for a rush job,
We put pins in between the flutes of the tap and kept wiggling it around until it came out, but it required a lot of expletives and angst to finally get it out. IIRC, it may have been old-school bobby pins, but for sure the tap wasn't jammed too bad, but nothing was sticking out either.

Also saw a guy weld a nut onto the protruding piece of broken stud or tap, combination of heat cycle and better leverage worked ok on my brothers diesel rig.

No one size fits all solution though for sure.
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Old 04-19-2013, 07:09 PM   #5
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I have removed broken HSS Taps with a carbide end mill and I have used a acid product ( available at machine shop supply ) if the tap broke in an aluminum part - otherwise EDM
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Old 04-19-2013, 07:50 PM   #6
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only other one I can add is the cutting torch. if the tap is broken off in aluminum you can blow it out with the ol fire ax. aluminum transfers heat way better than steel so if you heat the steel really quick you can burn it out of the hole with not too much damage to the aluminum, though you will probably need a helicoil. and yes, I have actually done this.

best thing is to not need this kind of anguish in the first place. tap with a good lube, turn in a half, maybe 3/4 of a turn, and then out a quarter, keep the chips cleaned out of the flutes.

as for broken studs... first is a left handed drill, if that doesn't work I try to drill it down the center "on size" , if I screw that up I helicoil it. I really don't even bother with easy outs anymore. a broken ez can be drilled with a cobalt though
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Old 04-19-2013, 08:56 PM   #7
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I've successfully used a broken tap extractor tool once before. it looks kind of like a socket with teeth that engage the reliefs in the tap.
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Old 04-19-2013, 09:15 PM   #8
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Quote:
Originally Posted by DaymienRules View Post
I've successfully used a broken tap extractor tool once before. it looks kind of like a socket with teeth that engage the reliefs in the tap.
Yes! True relief when it works. Patience is very important.
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Old 04-21-2013, 09:11 PM   #9
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drill the back side of the hole if possible, then whoop the drill bit of tap from there.

once its out, drill and tap next size (or two) up and chinese knurl the back side of the tapped hole.

then heat all thread and force it through, all the way with a little hanging out.

hack off the all thread, both ends.

center punch around the all thread, and the edge of the all thread. a lot.

peen the all thread flat.

file flat ( the edge cuts best and planes )

drill and tap the new hole, mo carefully.

most folks can't spot the repair. ;-)
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Old 04-22-2013, 06:16 AM   #10
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The broken tap problem lead to the Tapmatic:

http://www.use-enco.com/CGI/INSRIT?PMAKA=317-0726&cm_mmc=Didit-_-SEM-_-GglProd-_-GglProd&003=18299132&010=317-0726&{copy:002}&{copy:004}&{copy:005}&10=317-0726&gclid=CK2G1Zis3rYCFYMWMgodNWAAjg

Which is a wonderful tool if you are tapping many holes (but a bit pricey for the HSM). I have always tapped holes by hand using a guide or adapting a mill for the purpose - with plenty of cutting fluid and judging by hand force taps don't bread - but it is slow.

I think the job would decide how to remove the broken tap. Generally, work is done for profit and time is money so the quicker the tap is removed and threads formed the better. Machine shop forums are a better place to ask this question if you are looking for experience and ideas. YMMV.
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Old 04-22-2013, 02:54 PM   #11
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A few things about taps:

Always buy and use high speed steel taps. They're ground shiny all over and marked HSS. They're tough and strong. Carbon steel taps are cheaper, but they are hard as glass and brittle and break easily.

Taps do get dull after some use. When this occurs, don't use that tap to cut new threads, especially in aluminum or brass. You can use it to clean gasket sealer and dirt out of a threaded hole. Don't do this with a sharp tap if you want it to remain sharp.

Always use a tapping fluid. Kerosene works well for aluminum. I like Rapid-Tap for ferrous metals. Stainless steel needs a different lube. I've used Anchorlube for many years. It comes in a squeeze bottle and looks like green snot.

Always use a proper tap wrench so no side loading is placed on the tap. Back the tap up every rotation to break the chips off.
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Old 04-22-2013, 09:16 PM   #12
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This is all great info, thanks. I don't have a specific issue at present. I just wanted a better understanding of what options are available.

This last project involved drilling and tapping in tight spots on a bronze plaque. Some areas there was barely enough room to start and turn the tap. Also lots of odd angles so the risk of breaking a tap or drill was higher than normal.

Here the fastener was under the brim of a hat. I could not access the back of the piece.



(That's a missing canteen strap being replaced on a military monument. Yes, I know it's a simple tig job but if pins were originally used I drill out the old pins and do it the same way.)

I forgot about those tap removal tools. I'm sure, just like screw extractors, they work "sometimes". Still, it's another option to have on hand.

Again, thanks for the ideas- I knew this was the place to ask!
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Old 04-22-2013, 11:15 PM   #13
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For that job illustrated I strongly recommend an "extended tap wrench". Not only does the extra length really help, the longer handle makes it a lot easier to keep it in line.
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Old 04-23-2013, 02:47 PM   #14
Ironwood
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Cordless drill

I sometimes chuck the tap in a cordless drill with just snugging the chuck. It allows you to get steady pressure and a good angle on the tap. If it gets too tight it will slip in the chuck. And it is much faster as well.
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Old 04-23-2013, 07:06 PM   #15
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As long as you don't tighten the chuck, it works well. But I always use a
good cutting fluid.
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