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?

An EDM (electrical discharge machining) machine is usually the best tool for the job.

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.

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.

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

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

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.

Seriously, anything said is purely hit & miss until you fully describe the situation. We know not if it's a tap or a bit and nothing about the location or materials involved. It can be relatively easy or nearly impossible based on the total situation of factors. Lots of taps & bits get removed with no use of EDM.

I have used almost all of these methods, except for the EDM and acid, with varying success. I have always had the best results with a carbide end mill. Of course, how many home shops
have carbide endmills? Probably a small percentage.
Another method I have used is to shatter the tap with a center punch. This works pretty good if the tap broke because it is brittle or improperly heat treated. The center puch should be a good tool steel for it to work.
Prevention is the best course of action. Buying cheap taps will get you into trouble, as they aren't as sharp and might be brittle. If they aren't sharp, they will jam and break. Also, backing the tap out until the "chip" breaks off frequently will help keep the tap from jaming, and of course use plenty of taping fluid. Examine your tap for broken or chiped teeth before you start

I have tried that method...it always left a broken tap in a completely f'ed up hole that could no longer be removed with any method other than our portable EDM.

I could see it working in thin plate where you only need to break a couple threads of the tap to get it to come out the other side. It has not worked for me in heavier materials.

To me, it is not even a viable option any more...YMMV.

Sorry it hasn't worked for you,I have done it a bunch of times.

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. ;-)

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.

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.

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!

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.

I like.

Gonna add one to the tool kit.

There are also tap sockets available. They have an internal o-ring to hold the tap in. Handy for inaccessible locations.

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.