Broken Bolt & drill bit

bitbreaker

In trying to repair my dual stage snow blower I somehow managed to cross thread and break off the bold that holds the pulley on crankshaft. I also managed to break two (yes two) small drill bits off in the bolt while trying to drill it out. Any suggestions? The crankshaft is 5/8's in diameter with a 3/8's bolt.

Wood Butcher

Hopefully they were soft, junk drill bits

got to a REAL hardware store and get drill bit made for hardened steal and a screw extractor ( easy-out) and cutting oil (or at least WD-40) Take a center punch, and put a good solid dimple into the center of the bolt/broken bits and drill into the dimple, applying lots of lubricant. Then tap in the easy out and turn as to the left, as if you were using a ratchet to remove the bolt

End Grain

If the bolt is harder than the material it's threaded into, you probably cross-threaded the hole in that material and NOT the bolt itself. So, even if you do extract it cleanly, you may have to have the threads inside the orifice chased out and cleaned up - that's the best case scenario - or the hole drilled out and then threaded to accomodate a larger thread size. Hopefully, it's the bolt that's softer.

wire_twister

I have had success in drilling out broken drill bits, easy outs, and taps with a carbide tipped drill bit, generelly known as masonry bits. Get two or three they will wear down, but they will do the job. Once you get the bolt/bits out chase the threads and you should be good to go.

__________________
Jimmy

Life is tough, Life is tougher when you are stupid.

scrapiron

If the above ideas don't work come back and we'll try something else.

TransTech

I KNOW this will not be a popular reply.. but it worked for me.

In a moment of sheer stupidity I snapped a hardened steel punch off in a hardened transfer case shaft. The worst possible scenario.

Drilling was futile.

Since the truck was mine, I fired up the cutting torch and applied it to the punch, nailed the oxygen as soon as I got a glow and literally just blew what remained of the punch right out out of the shaft, then quenched.

Whole process took maybe 7 seconds and I can't imagine it hurt the temper. Never even malformed the shaft. You couldn't even tell I did it.

As far as I know it's still running fine.. I sold it to a friend of mine years ago and he drove it for maybe another decade.

There's also an "erosion" process I remember seeing advertised & reviewed in car mags some time back.. It was pricey then and involved shipping and such.. I don't even remember what it was called, but I remember it got rave reviews.

Maybe this will ring a bell with other members here?

Good luck.

wswoode

What would the cutting torch do to an engine block? Would it crack the cast iron????

rustyjames

Yes, if you're skilled with a torch that'll work. the other process you're refering to is EDM: http://www.edmmachining.com/

wswoode

What's your suggestion?

wswoode

Are the Masonry bits as tough as Wire Twister claims?

Giles

Is there any part of the bolt sticking out past the part it is threaded to?