Removing broken bolt

Mark W. · Feb 25, 2009

Well I done broke off a bolt in my super a transmission housing removing a final drive. I thought I could drill it out and retap it. 3 drill bits later no success. Any thoughts? What should I be using for a drill bit?

Anonymous-0 · Feb 25, 2009

IN MY RUN IN WITH BROKEN BOLTS,IHAVE FOUND DRILLING HARDEN BOLTS JUST PLAIN SUCKS!!!!I FOUND ONCE YOU OVER HEAT THE BOLT IT BECOMES HARDEN AND YOU CAN'T DRILL THEM.I HAD MARGINAL SUCCCESS WITH TITAINIUM COATED BITS AND COBALT BITS.YOUR GOING TO GET REAL GOOD AT SHAPENING BITS ON A GRINDER OR DRILL DOCTOR. OH,LOTS OF CUTTING OIL OR THE LIKE TO KEEP THE BIT COOL.

John B. · Feb 25, 2009

They make a welding rod that will aid in the removal of broken bolts. The welding rod won't stick to the cast but it will stick to the bolt. You weld a nut on the top and they say it screws right out. I've never tried it but I would check with your local welding supplier to find out more. Good luck!
John

steve in ok · Feb 25, 2009

John B is right. Welding a nut onto a broken bolt is the only way I take them out. The heat will break the rust loose and it will come right out. I use a wire feed welder and a nut that is about the same size as the bolt. That will help protect the cast housing by covering it.

Anonymous-0 · Feb 25, 2009

A solid carbide drill bit will work. They are rather expensive, but do the job. You can blow it out with a cutting torch. The cutting torch will not cut the cast iron. This is not recommended if it is your first time doing this, unless you practice on something first. Stan

1936 · Feb 25, 2009

Voice of experience talking here. NEVER and that is a long Never break off your bite in the hole. Then you need the toarch to blow the bit and bolt out of hole by one who had done this. Tap threads and use a number 3 or 4 bolt. In your case I would suggest replacment of all used bolts and tap each hole. Just not worth having the old bolts working out.

Feed back on your venture will be good.

bc · Feb 25, 2009

Question: If drilling on a bolt, would you use a slow or fast speed?

Mark W. · Feb 25, 2009

Thanks for all your helpful replies. It is broken down in so I cannot weld it. Going to go get the hardest bit I can and have at it.

RodinNS · Feb 25, 2009

I normally just use a good High Speed Steel drill. Cleveland is one example...
You'll probably want to start small and then enlarge it. Drill right through it. Drill SLOW. Get it enlarged right out to the thread. Then try an easy-out. If that doesn't remove it easily, put a welding tip on the torch and reach into the hole and make the remainder of the bolt glow. Watch and you should see the threads glowing. Then drive the easy-out home in the hot remnants and turn it out HOT.
I use the square Proto easy-outs. They're cheap and disposable which is what you need for that job.

Rod

relaurain · Feb 25, 2009

Left-twist drill bit. Heat the case with a torch, spray WD-40 in the hole and drill the bolt with the bit pushing hard. If you are lucky, the bit will catch and spin the bolt out. Very nice if it works. I did this many times but there are the times it won"t work.
Use a bit just a little smaller than the bolt not to screw-up the threads!
Good luck!

Brian Allen · Feb 25, 2009

bc
Slow, "the slower the better"!
Lots of "cool tool", (or whatever you use).
Brian

Dave anderson · Feb 25, 2009

get a hold of a lawson dealer and ask for a cronaweld eagle 3330 eletord kit. If you are using heat let it cool slowely so you don't harden the bolt. then drill it. next put heat on it and cool it fast this will pull the bolt away from the casting. Us a easy out to pull it out
Lawson 704-598-1225

Removing broken bolt

Mark W.

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Anonymous-0

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John B.

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steve in ok

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Anonymous-0

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1936

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bc

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Mark W.

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RodinNS

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relaurain

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Brian Allen

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Dave anderson

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