Broken thread tap in block....

Bassman/NZ

Bassman/NZ

Well-known member
In the process of removing head studs to replace the short ones with long ones, I managed to get a 7/16 UNC tap broken about 1/8" below the deck. I've searched this topic, and come to the conclusion my only option is to go hire an oxy/acetyline set and cutting torch, and blow it out. Taking the engine to a rebuilder is not an option, and I dont have a tig welder, so hiring a gas plant is the only thing I can think of.
Just relating this in case anyone has an idea I've overlooked. I've tried a small cold chisel and various punches, tried a cobalt drill. I think the tap has got hung up on something (I might have gone too deep) 'cause it dont wanna move. I drilled and tapped all the others no problem. Yes I know you shouldn't tap them, but I soaked them for two weeks in 50/50 mix, heated them, ran candlewax into them.... I guess they've never been out in 55 years.
 
Get a tool called a tap extractor. They are made in 3 and 4 flute designs. I've gotten several out with them. They look flimsy and you wouldn't think they would work, but they do.
 
I have had success with tap extractors as well. Just make sure it's a good one, not a junker from China that will break and make things worse. Try turning it lightly first one way and then the other. This will help to dislodge whatever is binding the tap. Use some light lubricant like Marvel Mystery Oil or 3 in 1. Patience is the name of this game. Good Luck!
 
I like the looks of those tap extractors, but I dont know if they will work in this case. The tap seems to be hung up on something and is in as solid as a rock. Also my efforts at breaking it out have resulted in a pretty mangled tap! :o
 
get your welding torch out and fing the smallest welding tip you have, set the tip to a long blue flame, put the flame directly on the tap and heat it red hot, the extractord are very hard steel with a lot of carbon content, when heated red hot they will crunble and then you can pry out the chunks with dental picks
 
tap extractors work excellent,definitely need a good one.if you do use a torch you may melt the threads before the hardened steel tap.if it's only a short piece of the tap you may be able crack it with small punches or chisel tips.in the future when tapping holes 1/2 turn in 1/4 turn back and lots of thin oil,remove and clean tap every few turns.good luck.
 
Option 1
If you could get your hands on a magnetic base drill a good option is to drill the tap out with a carbide drill take it slow lubricate and it should drill right through it; the bits are expensive but work great if you don't force em.

Option 2
I have also had good luck with a carbide tipped drill (masonary bit) if it has never drilled concrete, these are cheaper and don't shatter like a solid carbide drill. you could use the masonary drill bit in a hand drill start out centered with a small bit and work your way up.

A solid carbide drill bit needs to be more stable such as a magnetic base drill IMO; my first choice would be option 1, wear safety glasses as solid carbide drills can shatter.

I think ford3 also has an excellent idea although I have never tried it.


Regards,

Brian
 
Gas torch works just fine. I have done this many times and you can't damage the block or threads because oxy/act will not cut cast iron.

Heat the end of the broken Tap to bright red colour, do not look over the hole and wear full protection over your head/face and the arm/hand holding the torch. When you depress the oxy stream lever the gas will blast through the Tap and blow the hot metal upward, what goes up must come down and that will be over you. Move the torch around the hole to blast as much debris out as possible.

When cool pick out the small balls that will stick to some of the threads, often there are only a handfull of them and they come away easily. Clean the threads with something other than a Tap, which cuts away material that is required to make a good seal with the head studs or bolts, a Thread Restorer is a preferable tool to use.

Have someone film the process and post it on here.
 
I also have removed broken taps in a mill with a solid carbide end mill, but when I couldn't get the piece on the mill or I couldn't clamp it down, I used carbide burrs in a die grinder. With great care you can weaken the tap and break it out, but it usually takes several carbide burrs. The heat idea sounds interresting; maybe heat it up and draw the hardness back then the burr would work better. Just thinking out loud.
 
when i was doing my aperntship the mech i was helping taught me this .when your going to use a tap grind a circle around it near the top a little before the square. this way if for some reason the tap is over strained it will brake at the grinded spot. whitch makes it e z to remove .onley use taps made in the usa or germany or swiss
 
I'd put a washer over the hole and weld the tap to the washer. Then weld a nut to the washer. I've used this method to get out broken studs. Should also work with a tap. Good luck.
 
In my expirence that most taps are broken when trying to back them out.
Allways start the tap straight, and lots of good threading fluid. Not oil.
Start with a starting tap. Then a middle tap. Only then with a bottom tap.
As mentioned above NOT RECCOMNEDED for blocks. Instead, buy a new grade 8 bolt, and cut 3 or4 slots length wise across the threads with a drimmel rotary saw. Then use that tool only for cleaning the block.

Good luck

Bruce

Works good
Lasts long time
 
when i posted about using a torch to get broken taps out i didn mean to use a cutting torch, just the smallest welding tip you can get with a bright blue flame, when the flame is applied to the tap it will turn red hot and start to bubble, the flame doesnt hurt the threads in the block because its applied to the tap, after things cool down you can dig the pieces out with dental picks and a jet nozzle, i have never tried to remove a tap with a cutting torch but i dont see why it wont work
 
If you can get a little liquid nitrogen you might be able to shrink the tap without shrinking the block (keeping the block warm somehow? lightbulb heat?). Using a gas torch sounds a little hazardous as i think they can cut iron (ask not how i know:( but might work if the nitrogen does not.)
 
Bassman , listen to the Aussie ............ Fe26 has it exactly correct !!!!
Thats also the best way to remove broken studs , only drill an 1/8 hole in the stud first & then blast it out with the gas torch!!!
Cheers
Tony
 
I have also had sucess with an Electro-Arc tap burner. This is a machine that uses an electrode that is attached to a head much like a drill press. You select the electrode based on the size of the broken tap, stud etc. The electrode burns out the tap. The head uses water to cool the electrode and can do very precise work. Some older machine shops may still have one of these around. As previously mentioned a torch may work as well. The tap burner just gives you more control.
 
mrtexas said:
I'd put a washer over the hole and weld the tap to the washer. Then weld a nut to the washer. I've used this method to get out broken studs. Should also work with a tap. Good luck.
Click to expand...

+1 on this. I've done it with taps and studs. I use a MIG. The trick is to get a good weld and use a big, concaved shock washer. With a good weld and while it is still red hot, grab it with a Vise Grip and twist it out.

You said the tap is below the deck. The concave washer will help you center the weld onto the tap and not mess up the threads. Good luck.
 
Several years ago I had a broken exhaust manifold on the 413 Dodge engine in my motor home.. In the process of removing the manifold, two bolts broke off in the head.. In an attempt to drill the bolts and use a bolt EZE-OUT, the EZE-OUT broke in the hole.. Everyone I talked to told me to remove the head, taking same to a machine shop.. I finally stopped by a shop that I deal with from time to time, the man that owned the shop was an old time "no nonsense" mechanic..
Ken asked if I had an oxy/acet cutting torch, I said I did.. Ken told me to use the smallest cutting tip for the torch that I had, heat the object to cherry red and hit the oxy lever... The broken tap/eze-out will explode out of the hole. Clean up the treads with a tap and install the manifold..
Very truthfully I thought that Ken was nuts, however I was desperate, I put on my leather welding cape, face mask and gloves, lite the torch and tried to muster up the nerve to "blow" the EZE-OUT, out of the hole. Just as Ken said, when the object got cherry red I hit the Oxy trigger, POP!.. the object was gone.. I used a dental pick to remove the few small objects left in the hole, ran a tap through the treads and reinstalled the manifold.. Piece of cake.. I did use Lok-tite on the bolt threads just as a precaution...
 
You must log in or register to reply here.
Back
Top