ACK! Removal of broke thread tap?

Mike CA · Oct 31, 2009

I drilled out the broke stud. I think I was just a touch off center, but still usable. So, I started to tap the threads. I was doing well. The tap was cutting well. Then it snapped!! I had no indication is was about to snap. Just POOF, and I'm sitting there with my jaw open!

So, I figure I'm gonna have to drill it out and start over... but the drill won't penetrate it!

What do I do??

ScottyHOMeY · Oct 31, 2009

How far down in did it break? You'll play the devil tryin' to drill it.

If you weren't winding on it hard, and it isn't recessed too far, you might try starting it back out by tapping counterclockwise on one of the hollows in the tap with a small punch. If you were to try a drill, it's have be a very hard one and a left twist bit, but those aren' easy to find in the kind of hardness you'd need to actually cut metal, but the left twist might grab enough to get it started.

There are also some specialy tools, basically a spanner type, similar to the tool for butting rings onto the collets of angle grinders, that will get down into the recesses on a tap to wrench it out.

Wardner · Oct 31, 2009

Geeze, Mike,

I don't recall anyone telling you to chase the
threads with a tap. You failed to follow
instructions. Your on your own now. Have you
thought about buying another head? How many EDM
machines do they have on base?

glennster · Oct 31, 2009

mike, if you have any tool trucks, snap on, mac, matco, cornwell, ect get a broken tap extractor. looks like a tube with 4 notches on the end to engage the broken tap. ortherwise, high speed grinder like a dremel.
tap extractors

Dr. Bert · Oct 31, 2009

Mike CA: When that happened to me, I took a pair of good quality needle-nose pliers-ground down the jaws a little-so they would fit in the grooves of the tap and with firm, steady pressure on the handles backed the tap out far enough to grasp with vise grips. May work for you--Good luck.

Mike CA · Oct 31, 2009

Pretty deep. Almost all the way the way through. :?

Mike CA · Oct 31, 2009

(quoted from post at 17:02:38 10/31/09) Geeze, Mike,

I don't recall anyone telling you to chase the
threads with a tap. You failed to follow
instructions. Your on your own now. Have you
thought about buying another head? How many EDM
machines do they have on base?

I was told by a club member who helps me.

It's not the head, it's the block.

I have no idea what a EDM machine is. I'll have to figure that out and find out.

Wardner · Oct 31, 2009

For EDM Machine, click below. Google also has a
title for building your own EDM. I didn't read it
though. Maybe your kids could learn something by
building one. You gotta love home schooling.
EDM article

Phillip Howard · Oct 31, 2009

If all else fails check machine shops in your area there is a machine that will cut that tap out without getting it hot.

Joe B2 · Oct 31, 2009

You can forget drilling a tap,the only way you can possibly drill it is with a carbibe drill(masonry) then it will try and run off to one side.What size is the tap?There are several ways to try.When all else fails,pull the head and take it to a machine shop,they will have a bridgeport set up or something simalar for that very reason,burning out broke taps.Nothing wrong with running a tap in a hole that had a bolt drilled out.I would have done the same thing. Being a machinst,with over 30yrs experience.Always use a lite oil as cutting fluid.They do make tap extractors for the size tap you were using and sometimes they work.

gene bender · Oct 31, 2009

There isnt any way you will drill it out as the tap is harder than the tap. Get a dremmel tool with carbide 1/8 cutting tool and be careful.The tap extractors arent that great depending on how bad the busted tap is stuck.As a maintenence person on third shift had way too many to remove lots of tricks mite be better taking it somewhere to have it removed will save you lots of money buying tools ect and keep you from ruining the part.

26Red · Oct 31, 2009

That happened to me on a H block. I took it to a neighbor"s shop and he used a cutting torch to melt the tap and blow it out. It was a through hole though. Pretty skilled guy to do that!

Anonymous-0 · Oct 31, 2009

Can you weld a nut on it , and turn it out?

Wardner · Oct 31, 2009

Joe B2. I would never run a 5/16th tap in such a hole unless it looked perfect to begin with. And then it would be a bottoming tap. I think Mike thought he could cheat his way to good threads.

Under some circumstances, I might cut flutes in a higher grade bolt and use it like a tap to see if I could get the
remaining threads to move. That bolt won't break but if it did, it could be drilled out.

John G. Hasler · Oct 31, 2009

> Under some circumstances, I might cut flutes in
> a higher grade bolt and use it like a tap to see
> if I could get the remaining threads to move.

I like that idea. It"s a pretty good idea way to make a thread-chasing tool for general use. It will clean the threads without shaving off as much metal as a sharp tap would.

Anonymous-0 · Oct 31, 2009

Presumably you are not serious Wardner. Give the guy a break! He needs support, not grief from the peanut gallery.

Wardner · Oct 31, 2009

I hesitate to mention this because I don't know
exactly what the problem is.

I am assuming that the hole is a through hole into
the water jacket because you are working on the
block. Yes, a torch will work but you haven't got
one. Cast iron will not oxidize as fast as steel
when one hits the oxygen lever. I torch out steel
pipe from iron fittings all the time.

You said there is only a small piece of the tap
and it is near the end of the hole. Let's assume
that the last 1/3 of the hole is expendable.
Let's also assume that the cast iron surrounding
that 5/16th hole is about 1" thick. That's
reasonable because the pattern maker would have
beefed up areas around tapped holes.

You could take a piece of 1/4" pipe (that's a
nominal size, actual size is over 5/16th" on the
ID), cut it to fit between the inside of the water
jacket and something solid. If there is nothing
solid, put a piece of heavy flat bar in there as a
bridge. The pipe gets centered on the hole and
is tight. Now drive the tap through the cast iron
into the pipe.

Install the new stud with Threadlocker or epoxy. I
think 1/2" of thread in the cast iron would be
enough but you will probably have more. I don't
think you will have a big divit on the back side.
Just four small thread tear outs. If you are lucky
the only damage will be to the tap as it shatters
into small pieces.

If you are not lucky, and you cave in the whole
side of the water jacket, will you forgive me?

SGT K · Oct 31, 2009

Mike,
I've been there. The first thing to do is walk away for a few minutes.

I would try a punch first - sometimes you can break them into smaller pieces while you try to back it out. If it's flush try to weld a nut to it. Sometimes the heat really helps.

If all else fails I'd take a torch to it. I know it's a blind hole, but I've done it before. Wear good eye protection and get the tap red-hot then put just a little O2 to it. Is it a 5/16? The smaller it is the more difficult it will be.
Good Luck

ScottyHOMeY · Oct 31, 2009

No idea about the cost, but if nothing in your toolbox works, that Walton extractor looks like a pretty good option. If you're just in hand tight, I've got an idea it will be some expense but will get it out and be one of those tools that will wander around in the toolchest that you'll never need again.

Somebody mentioned in another thread, and I don't know if your work puts you in proximity to buddy up with any of the machinists on base, but that might be a source for help/advice/borrowing a tool.

Janicholson · Oct 31, 2009

This will do it with patience and calm, sure, attitude.
Purchase a good 120vac powered Dremel tool Pawn shop is OK if it works and has a good 1/8th inch chuck/collet.
Purchase 1/8th inch shanked diamond tool for the Dremel. It should be at 1/8th, or 3/32" diameter, and shaped like a small cylinder, or pointed with the widest part no bigger than an eighth inch.
This will grind the tap very successfully. Start in one of the flutes (gaps in the hard part), and grind away the center of the tap from outside to inside, Stay away from the engine casting, and do not hurry at all. once the center is ground out to the depth of the diamond, go deeper until the center is actually gone. This can take 2 hours, and several rests to avoid hurrying.
The pieces will fall out (or can be picked out with a dental pic) when the center is gone.
The EDM machine is a great tool, but requires the block to be submerged in dielectric fluid, and laying on its side. Best of luck, and your mistake included the a bit off center, and not going forward no more than an eighth turn and back a quarter turn to clear chips.
Learning by snapping off a tap is a great method of avoiding it in the future. All is well! JimN

Mike CA · Oct 31, 2009

Since I'm in way over my head...

I went to a party held by a metal worker/tractor restorer in my club. I told him of my woes. He said next time we'll weld a nut to the broken stud first. Live and learn. He also said drilling was useless, for the same reasons mentioned in here. He's going to come over, probably on Tuesday, and look at it to make an assessment. So hopefully he has some tricks up his sleeve.

I'll mention the ideas about the Dremel tool/diamond head, and the torch.

Thanks guys, wish me luck on Tuesday. Meantime I'm going to just clean tools and rebuild my carb to keep me occupied and moving forward.

glennster · Oct 31, 2009

another thing to remember, if you are cutting new threads, use a tap and die set, however if you are just cleaning up something already threaded, use a thread cleaning tap set. they are different. heres a link to some summit sells, but any of the tool trucks will have sets or sell indviduals.
thread cleaners

Janicholson · Oct 31, 2009

One word on the Dremel, do not put much force on it, and keep the cut clean (air , or a squirt of carb cleaner to rinse out dust. Forcing the diamond will heat it and melt the shank of the bit. It will not hurt the diamond, just the matrix holding the particles of diamond. Two hours is about right!! JimN

John G. Hasler · Nov 1, 2009

> Forcing the diamond will heat it and melt the
> shank of the bit. It will not hurt the diamond,
> just the matrix holding the particles of diamond.

If it is really diamond getting it hot while in contact with iron will dissolve it away.

Joe B2 · Nov 1, 2009

Being how it is only a 5/16 tap,you might get it out with a tap extractor,blow a lot of compressed air in the hole first to loosen all the metal shavings or trybacking it out with a punch that is pointed on the end.If all else fails hit the center of tap with a good punch in the center and try and crack the tap,use compressed air and a small pointed awl or something simalar to move it around and get the peices out,if you were around middle Tn I would get it out for you.

Dblair · Nov 1, 2009

find a machine shop that has one of these
it's a potable edm machine

Joe B2 · Nov 1, 2009

Guys, when you are tapping holes always,always use some sort of cutting fluid,motor oil,WD-40.Kroil,anything to lubricate the hole and keep backing the tap up to help break the chip.That is why the tap keeps getting a little harder to turn,is it is starting to load up with chips,Small taps are very easy to break,plus most use the cheapest they can find.When hand tapping,never go a full turn without turning it back till you feel it break the chip.Take your time when hand tapping and start them straight.

Wardner · Nov 1, 2009

Mike has a sense of humor so don't worry about him.

I suppose we should have warned him in his previous post about using a tap in this situation. The board did tell him to use dental picks.

The use of the word "cheat" was probably out of place. "Easy way out" would have been better.

Dave_Id · Nov 1, 2009

dblair has the right solution. EDM is really the only good way to remove a broken tap. If your tap is a carbon steel or M2 high speed tap, then you may be able to remove with a carbide burr, but a torch won"t touch an M8 high speed tap, and you may just destroy the casting in the process. You probably had a cracked tap that it would break that easily or one that was mfg"d in China and improperly heat treated.

Jake Winn · Nov 1, 2009

I would agree these are a great investment. I have a set up to 3/4 inch. They have saved my bacon several times.

oldtractorsrock · Nov 1, 2009

Been there done that! I broke a 1/8" pipe tap in a casting recently. Tried most of the above methods. carbide burrs are expensive and trying to get out taps ruins them pretty quick. I got a couple of packs of chain saw sharpener stones and used them in my die grinder the same way you would the carbide burr. These stones are available at most places that sell chainsaws. They are standard 1/8" shank, will fit a dremel tool or diegrinder with the proper collet. Take your time and wear face protection these are pretty fragile. The best part is they're cheap! Good luck!!!

ACK! Removal of broke thread tap?

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