Trying not to break a tap could easily be one of the most stressful situations in metalworking. It happens to everyone, regardless of how long you’ve been doing it.
A tap stuck in material is an absolute pain to remove, no matter how you look at it. Taps are hardened steel (unlike bolts), so they’re never fun. It’s very rare that it comes out easily, but there are a whole bunch of tools and methods out there that can get the job done.
Generally speaking, broken drills are much easier to remove from holes, since there’s much less contact between the workpiece and the drill compared to taps.
In this article, I’ll give an overview of some of the ways that you can solve the problem, what situations make them practical, what kind of results to expect, and some tips on how to make them work better.
Please keep in mind, though: a threaded hole that’s had a broken tap jammed in it will pretty near always have, at the very minimum, some scars to show from the ordeal. Or, you might have to do some all-out thread repair to get things working again.
Hammer and Cold Chisel
It’s cheap and ineffective, but it sometimes works. This is not a good idea if the tap is deep in the hole (where it usually likes to break). This can work well enough for removing drills.
You will trash your hole by using this method, so you’ll likely need to either do some thread repair (more info below) or drill and tap one size up.
Also, make sure you’re using the right kind of chisel. Cold chisels are hard but not brittle, so they’ll tend to be cut instead of snapping like a woodworking chisel. Here’s an example of a good kit for tap extraction. Keep in mind that you will be putting some heavy wear and tear on your tools.
You could also use a center punch if you have one. It’s made out of basically the same stuff as a cold chisel. You’ll probably have to grind it to modify it or to restore it.
Success rate: 15%
Needle Nose Pliers, Lube, and Heat
If, for whatever reason, the tap has broken fairly close to the surface and it’s not too deep in the hole, then this might actually work. If you can get a decent grip on the tap with a set of needle nose pliers, then this is worth a shot.
This is one of my preferred methods for removing broken drills.
First off, add something like WD-40 or a light oil to the hole in question. Try to grab on to the tap as best you can with the needle nose pliers, and give it a gently wiggle back and forth. Keep in mind that you’ll probably chew up/bend/trash your pliers, so don’t expect them to last.
If it’s not budging, try heating up the material that it’s stuck in. When you heat it up, everything will expand a bit, and it might be enough to loosen the material’s grip on the broken tap.
Success rate: 20% for taps, 80% for drills
When they work, they work great. When they don’t, they don’t.
Tap extractors pretty well always have mixed reviews. Some are better than others. That said, they’re reasonably inexpensive tools and are always worth a drawer in your tool chest.
These generally are only for straight-flute taps (common on hand taps). If you’ve broken a spiral-flute tap (common on machine taps), then you’re generally out of luck for a tool like this.
There are a few different varieties out there. If you’re looking for the cheapest option, you can get a basic 3-4 flute extractor set like this one on Amazon.
If you’re OK with paying more for something that will work better, then you should check out the Walton tap extractors (this one for 3-flute taps and this one for 4-flute taps). Make sure you read through the kit to make sure it’s the correct size and style.
Here’s a video of one of these more expensive tap extractors working:
I will point out something that I see people doing incorrectly with these tap extractors:
Don’t use them if the tap is half sticking out of the hole. Use vise grips and work it out that way instead. Use this tool when the tap is broken nearly flush with the top of the metal.
The reason for this is that the drilled hole actually gives support to the tangs of the tool. If the tool is used outside of the hole, there is no support on the tangs, they’ll splay open, and you’ll wreck the tool.
Success rate: 15% on the cheap tool, 75% on the more expensive one in the right conditions.
If you have a TIG welder and you’re feeling brave, this actually works pretty well, provided that the broken part of the tap is relatively near the surface.
This can work similarly with broken drills.
If you heat up the tap slowly, you can actually soften it up a bit to make it less brittle. Use a stainless filler rod and patiently build up a bit of a nub that you can grab on to with vice grips and back it out slowly.
Here’s a video of Jody from weldingtipsandtricks pulling this off successfully. He does a great job of explaining how he’s doing it. The only thing that I would do differently is that I would use some WD-40 and let it soak for a minute before backing it out, just in case. Otherwise, it’s a very good how-to.
Machining with a Carbide End Mill
If you have access to a milling machine, this will work. It might just break a few endmills and chew up the threads in the process.
This does also work well for broken drills.
I strongly prefer using a CNC mill for this, since they’re a lot more rigid, but you can pull this off well enough in a manual mill as well.
I’ve had reasonable success by using an SFM of around 400 for a carbide endmill on a HSS tap and feeding with the handwheel slow and steady at .0001″ graduations. Lots of coolant.
For a manual mill, use the same principle. Watch carefully for tool deflection, and keep everything as short and rigid as possible.
Keep an eye out for chunks of the tap dislodging. I like to feed down a little bit, inspect for any pieces that could be tapped out with a cold chisel or pick, and then keep going. If these aren’t removed, they’ll snap off while your tool is in the hole and break your endmill.
Success rate: 90% with a few broken carbide endmills and mangled threads.
This, in my opinion, is the hands-down most reliable and cleanest way of getting a broken tap or drill out of a hole. I’ve removed hundreds of broken taps this way, and it works pretty well every time.
An EDM works by erosion using electricity. As long as what you’re working on is conductive, it will erode it.
With this method, holes can be eroded into the tap or drill (or bearing or pin or literally anything else made out of metal) until it can break apart easily and be picked out or blasted out with compressed air. You can sometimes even use a magnet to extract some of the small pieces.
What can make this process tricky is if there’s small broken pieces or a lot of chips in the way that make the electrode short out. Generally, though, it’s not too bad.
The downside is that these machines usually cost upwards of $25k for even a basic model, unless you can find a good deal on a used one.
However, you can get some cheap Chinese machines that are designed for this specific purpose for just a few grand, like this one here. I’d consider them to be on the same level as the off-brand TIG welders, though. They work, but they’re by no means industrial.
Your best bet is to find out if there’s a local EDM shop that can do it for you. You can usually get them to take care of it for under $100 or so. At least, that’s what I used to charge. Every broken tap is different.
Here’s a video of a guy with a really old-school EDM that does this regularly. It’ll help you get your head around how the process works and what it can do.
One of the big advantages is that there are no cutting forces and the erosion is highly controlled. This means that it’s the least likely to damage the threads that the tap is jammed in.
Success rate: 95%
USE EYE PROTECTION!!!! Actually, a full face mask would be even better. Taps very easily snap and go flying at eyeball-cutting speeds. Using gloves and other PPE is a good idea, too.
Sometimes the easiest way to deal with a broken tap is to cut around it, repair the material, and try again. You might be able to use a trepanning drill, hole saw, or CNC to remove the material around the tap and then put fresh material in its place. This usually makes sense for smaller holes that aren’t critical.
If welding is an option, you might be able to get something to work. Just keep in mind that the welded material will be harder and less consistent than the base material, especially with steels. You might want to try annealing the steel if possible.
There are some other mechanical options, too. For example, you could screw in a plug and drill and tap a fresh hole. Try looking up blank Keenserts for this option. Or you could use an NPT plug like this one.
If you can keep the hole on center, you could also try something along the lines of a Helicoil thread repair. This is more so for a fit for when you got the tap out but the threads are too mangled to use. You can buy them at Amazon (like this one) or possible from a local hardware store. If you’ve never used one before, please take the time to read the instructions. I’ve seen a lot of guys use the installation tool incorrectly.