[kutyafal]

A friends D60 cast in spring perch has a broken bolt in it. Probably a 5/8 or 9/16 grade 8 bolt. He has already drilled a 3/8 hole in it that is a bit off-center and tried an Easy-Out with no luck. The hole can not be drilled any bigger without ruining the thread. What other options does he have? What would be the best way to try to cut a vertical slot into the bolt stub from the inside? That way it could shrink some more once heat/cold is applied. Inventive ideas welcome. We've already tried C4...

 

[elusive]

if you can get to the top of the broken bolt at all.... you can weld another bolt to it..the heat from the welder helpd a lot.. and noeyou can put a wrenck on the new bolt..

 

[Jim_Lou]

I would continue the hole already started until it's all the way through the broken stud. And use a left hand drill bit to do it. That might be enough by itself.

If not, the next step would be heat from a small tip on an acetylene torch. Try to get the heat to go straight down the hole. The heat will actually expand the bolt, making it tighter in the hole, but when it cools it will be a little looser. It might take several cycles of heat and cool. It will cause smoke, but some penetrating oil in the hole could help, too.

If it still won't come out, heat the whole area around it, and then stick an icecicle on a toothpick down the hole. Cool the bolt as quickly as possible, and it should come out.