Broken tap

[cr17]

Ok I need help here. I broke off a 4 flute 1/4 tap in the %%##^%# hole - well below the surface in a piece of aluminum. Any recommendations on getting it out? Walton tap extractor? EDM if I can find it, anything else? Anyone tried the old alum method. Did I mention %#^#^##^#

Thanks

[mike in co]

there is a kit sold for this. try a couple of the online machinest stores. emco, grizzley.

or buy a dremel type tool and a couple small carbide bits. cut the tap in pieces.
go slow....

mike

[scb]

Yea, being a 1/4" tap you may be able to cut it out with a carbide burr in a dremel tool. I've done it. But like mike said go sloooow. If you break that carbide burr off in the hole then you are screwed. Done that too. I haven't used it but MSC is selling a carbide drill set specifically to drill out broken taps. If it one of those "must save" parts I think I'd give them a try. steve

[10-x]

How tight is the broken tap in the hole? Were you cutting threads or backing it out? Is it a blind hole or through hole? Blind holes are hard to deal with.If backing it out try the tap extractor using acetone as lube. If cutting try tapping on the broken end of the tap with a small pin punch and a small hammer to loosen it up and then the extractor and acetone.
Another reason to use 3 flute taps.
Good Luck

[johniv]

GO SLOW, I havent used the new tap removal stuff for sale now, but years ago I brok a 1/4 " tap off flush in a hole (blind) and a MASTER welder in the shop TIG welded a small pillar on top of the broken tap and forked the top, it was then removed with a plier. key word here is MASTER welder.
also it was broken in a steel workpiece so this may not be possible for you. Just my 2 cents worth.
I feel yer pain.
John

[Sam]

Get with your dentist and get your hands on some old dental burs.
They are diamond an dcut much better and are easier to control than carbides.
They will easily remove the worst broken taps.
Instead of cutting off the "webs" of the tap cut straight down the center and then cut outward. They break like glass.

Unless you are really really really good at it never use HSS taps.
Broken carbon steel taps are much easier to remove:-D

Sam

[JIMinPHX]

You’re in luck because it’s in aluminum. Put a 5/16 nut over the hole & stick a mig welder down in the center of it & weld the tap to the nut. Don't be shy with the heat. About 5 seconds after the orange glow goes away, turn it out with a wrench. Steel mig wire doesn’t stick to Aluminum & the heat from the weld will expand the aluminum & loosen the tap. Aluminum expands much more than steel does when you heat it. I’ve done this for broken exhaust bolts on Harley shovelheads several times. It works great.

[Lloyd Smale]

you just taught an old dog welder a new trick. thanks!
You’re in luck because it’s in aluminum. Put a 5/16 nut over the hole & stick a mig welder down in the center of it & weld the tap to the nut. Don't be shy with the heat. About 5 seconds after the orange glow goes away, turn it out with a wrench. Steel mig wire doesn’t stick to Aluminum & the heat from the weld will expand the aluminum & loosen the tap. Aluminum expands much more than steel does when you heat it. I’ve done this for broken exhaust bolts on Harley shovelheads several times. It works great.

[Bret4207]

Don't bother with the tap extractors. Do as Jim recommended or go EDM.

[dnepr]

I thought there was a chemical the would attack the steel tap but was safe on aluminum . For the life of me I can't remember what it is called . The idea is that you fill the hole with this stuff and it disolve enough of the tap to make it loose but this stuff doesn't touch the aluminum. It is supposed to be a slow process it takes somthing like a week to get the tap loose enough to come out.I remember hearing about the stuff but I have never tried it myself. The old memory isn't what it used to be.

[fishhawk]

what i have used in the past before i was "wealthy" enough to get the brownells tap extractors was nitric acid takes time but it does eat the steel and iron. it can be found in small quanities know as "aqua fortis stain" many muzzleoaders are stained with it after aplying it then heat. just not sure what it will do with alum.

[leftiye]

Lloyd, .... What do you weld on them dogs? (I know, .... couldn't resist)

[John Taylor]

Have removed many broken taps with a milling machine and a carbide end mill. I use old broken end mills and sharpen them like a cold chisel. Run the RPMs higher than normal and you can drill right through the center of the broken tap and then dump out the pieces.

[cr17]

Well I should give an update. I went for Jim's solution but I can tell you that convincing the local welder was a challenge. (Mind you this was all in French, and my technical welding vocabulary is nil.) Neither he nor his father, an old machinist from the logging/mining camps up north, believed it would work. In fact, he bet a gallon of maple syrup that it would ruin the whole piece. So no I have a gallon of maple syrup coming when the sugaring starts, a piece that I can use ( I buggered the hole in my ham handed attempts to get it out) and a new technique.

Thanks all

[scrapcan]

Sounds like all worked out well. You will ahve a lot of use for the gallon of maple syrup. and best of all I got to learn a new technique also.

[JIMinPHX]

I’ve also got another little broken screw removal trick that involves a cam shaft & a left handed drill bit that a lot of people tell me can’t work, until they see it done. That’s a story for another day. I’m glad that this worked out for you.

In the future, if you’re tapping 1/4" threads in aluminum, you may want to consider a roll tap (Also known as a thread flower, a forming tap or a Ballax tap). Roll taps make threads by displacing material rather than by cutting it. They actually swage the threads into shape. In aluminum, they make stronger threads because of the surface compression. These taps are also much harder to break because they have no flutes cut into them. They just look like a screw. If you use one of these, you need to drill a different size (larger) pilot hole. You also need to use plenty of thread cutting oil. These work great in aluminum, but they are not so good in less ductile & less malleable materials.

My second choice would be a two-flute spiral-point gun tap, if you want to stay with a “cut tap”. The gun taps are much stronger than a standard hand tap & take abuse much better. You also don’t need to stop to clear chips because they push the chips ahead in front of them. You just run them straight through in one shot. With a 1/4" gun tap, I usually just put it in the chuck of a cordless drill, dip it in oil & run it right through. The only down side to a gun tap is that they are not the best in a shallow blind hole because the chips that they push in front of them have no where to go. Gun taps can be had for pretty much the same money as a standard hand tap & they use the same pilot hole drills.

Since you have a half buggered hole already, you may want to go with a heli-coil or thread insert collar to fix up your current piece. These are not hack & slash repairs. Some of the aluminum aircraft parts, that I used to make, specified heli-coils in the original design because they provide a more robust thread than a straight tapped hole. The other tapped holes in aluminum aircraft parts were usually specified as roll tap only. You can get roll taps, gun taps & a good selection of thread inserts from places like MSC.

[MtGun44]

I have never needed it, and with modern fears about mercury, maybe
nobody would do it, but ---

Brownell's gunsmithing kinks book years ago said you could heat the
broken tap up to red head with a small tip acetylene torch and drop
a drop of mercury on it from an eyedropper to cool it ultrafast. Of course,
this would vaporize some mercury, so do it outdoors, etc., etc. or don't
do it at all.

They claimed it made the tap so glass brittle that you could break it up
into tiny chunks with a pin punch and pick out the pieces.

Never tried it, but it was so interesting that it stuck in my rat trap of
a brain,using a liquid metal to get a cooling rate faster than with water.

Bill

[EMC45]

I have always heard to use a selfloading punch and just pop it and it "should" break!

[Morgan Astorbilt]

This will work with carbon steel taps. HSS will just peen over. That's why I always use carbon steel in the small sizes, if available. These are sold by Brownells for this reason.
If in a bind, you can have it shattered, I think ultrasonically(some scope mount companies used to offer this service), or cut out with an EDM(this may be what they used).
Morgan

[JIMinPHX]

I usually just try to use taps that don’t break easily & treat them properly. When I was doing production work that involved tapping a 1/4-20 thread an inch deep in 6061-T6, I would get about 1200-1500 good tapped holes before I’d break a tap. The taps that I was using were not much more expensive than the ones you find at the hardware store. They were just better matched to the job at hand.

[bushka]

the best tapping fluid I ever used being a machinist was "tapmagic" with that cance causing stuff triclorethene

[grumpy one]

This will work with carbon steel taps. HSS will just peen over. That's why I always use carbon steel in the small sizes, if available. These are sold by Brownells for this reason.
If in a bind, you can have it shattered, I think ultrasonically(some scope mount companies used to offer this service), or cut out with an EDM(this may be what they used).
Morgan

I don't know whether HSS is brittle at low temperatures - many alloy steels are. If so, a liberal dose of liquid nitrogen followed by a smack with a punch would work wonders.

My method for removing broken HSS taps is very slow and fairly destructive of the original thread. I make a punch and use it to tap gently on the flutes in the unscrewing direction, rotating around the flutes in sequence so I don't cause the tap to dig in radially. The biggest problem is when you've backed it up about 30 degrees and have to break the chip. If I were a much more patient fellow I'd make an extractor out of alloy steel, designed to slide down the recesses between the flutes of the broken tap. Then I could apply a pure torque in the unscrewing direction, instead of a series of tangential forces (which is all I can apply with the punch).

As often as not, I end up having to break the tap to pieces, which I do by applying a punch axially. I don't have any particular problem breaking the tap - in my experience HSS is extremely brittle. Of course the pieces then won't screw out: they jostle each other and dig in radially. The next step is to break the pieces into pieces, and lever those out individually. Takes hours, and leaves the thread pretty hopeless so it has to be drilled and tapped oversize.

[floodgate]

Geoff:

"If I were a much more patient fellow I'd make an extractor out of alloy steel, designed to slide down the recesses between the flutes of the broken tap. Then I could apply a pure torque in the unscrewing direction, instead of a series of tangential forces (which is all I can apply with the punch). "

You can buy exactly what you describe; IIRC, they are called "Walton(?) Tap Extractors", and you can get spare fingers for them, which are oval in cross-section to match the flute and the curve of the threaded hole . Trouble is, you need different sets for 2-, 3- and 4-flute taps, and for each size tap you use - I started getting them, and found they add up in $$ (US, AU or NZ) pretty fast; and they still aren't perfect, if you shear one of the "fingers" off and have to extract it too.

My experience is altogether pretty much like yours.

Floodgate

[No_1]

Floodgate and Gentlemen,

RIDGID makes the same thing you just discribed.

R.


Geoff:

"If I were a much more patient fellow I'd make an extractor out of alloy steel, designed to slide down the recesses between the flutes of the broken tap. Then I could apply a pure torque in the unscrewing direction, instead of a series of tangential forces (which is all I can apply with the punch). "

You can buy exactly what you describe; IIRC, they are called "Walton(?) Tap Extractors", and you can get spare fingers for them, which are oval in cross-section to match the flute and the curve of the threaded hole . Trouble is, you need different sets for 2-, 3- and 4-flute taps, and for each size tap you use - I started getting them, and found they add up in $$ (US, AU or NZ) pretty fast; and they still aren't perfect, if you shear one of the "fingers" off and have to extract it too.

My experience is altogether pretty much like yours.

Floodgate

[JIMinPHX]

This will work with carbon steel taps. HSS will just peen over. That's why I always use carbon steel in the small sizes, if available. These are sold by Brownells for this reason.
If in a bind, you can have it shattered, I think ultrasonically(some scope mount companies used to offer this service), or cut out with an EDM(this may be what they used).
Morgan

I don’t know about the ultrasonic deal, but an EDM or it’s little brother, the spark eroder, will both eat through either HSS or Carbon steel & not wreck the tapped hole in the process.

[deltaenterprizes]

I have read that ALUM will eat the steel and not harm the aluminum.

[Newtire]

Since you have a half buggered hole already, you may want to go with a heli-coil or thread insert collar to fix up your current piece. These are not hack & slash repairs. Some of the aluminum aircraft parts, that I used to make, specified heli-coils in the original design because they provide a more robust thread than a straight tapped hole.

Just my 2-cents. We use Time-Serts instead of Heli-coils as they give a better hold on the work. Cadillac is using these to screw head bolts into. We did the heli-coil route on torpedo motor casings on one now-obsolete model when I was in the USN. These Time-Serts have Heli-coil beat hands down. You can even get them in oversize called "Big-Serts".

[monadnock#5]

This is an extremely interesting and informative thread. Great stuff from pros and advanced hobbyists. I do believe this thread belongs in the "Sticky" Hall of Fame.

The only tip I can offer is a front end suggestion. When you're into a project that you only have one chance to do right the first time, always, always, always use a brand new tap.

[cr17]

I agree with monadnock -- and I'm always amazed at the wealth of information on this site. Quick note though, don't bother with the alum. I tried various strengths for up to 10 days, and at moderate heat ( sat it on the furnace). The only result was that the aluminum turned black.

[uncle joe]

you just taught an old dog welder a new trick. thanks!

I had a guy remove a stuck and broken setscrew that was in a 4 foot diameter sprocket. It was about a half inch setscrew and the top of it was about 2.5 inches down in a hole. He took a stick welder and welded a little and chiped flux a little over and over til he could weld a nut on top of the hole and wrenched it out. My mechanic I sent with it said it was the coolist thing he ever saw. He also learned a valuable lession that we all have used many times.
I removed a broken quarter inch tap from a hole with an air arc tool once, removed the tap and left all the threads in the hole in tact. Thought I was hot S#*$ till I stuck another tap in the hole to chase the threads. The air arc rod had coated the hole with carbon, can't cut it with a tap, had to move the hole.
:(
it might not be easy to teach an old dog new tricks but if he's a smart dog you can learn new tricks from HIM