DSmith

I had an exhaust bolt broken so I drilled it out, everything is good right? wrong
when I chased the threads I was felt it start to bottom out, begain to back the tap out and after about 1 turn the tap breaks off 1/8" inside the hole. This is not a straight tap, it has spiral flues. Its much harder than the drill bit so how do I get it out?

8Mike9

Easiest way is to pull the head and take it in.

You can make a guide, but would require you having access to the other bolt holes, a chuck of steel, and the ability to get it all in.

It's tough to explain via typing, but I've used 1/4 inch die grinder bits through a jig, got a decent surface, then cut out the tap.

You have to get creative and take your time...or pull the piece and have the shop do it.

rsn932

I'm not familiar with this kind of tap. I'm assuming you can't use a tap extractor on it because it spirals somehow? Either way, spray lots and lots of penetrating fluid in there and try to get something down the flutes, either a tap extractor or some small allen wrenches and then turn them.

DSmith

Thanks for the input, the head is off the car.
This tap looks a drill bit with threads, its used in cnc machines for higher speeds. instead of breaking spall chips off which would fall down into the hole it curles them out of the hole.

rsn932

That's pretty cool for tapping...doesn't leave you much for getting a broken one out though. Someone else must have some ideas...

Apeiron

Maybe a pile of left-handed cobalt drill bits and a lot of patience?

Air_Adam

You're lucky... i can't even drill into my broken exhaust bolt... i ruined 2 perfectly good steel-cutting drill bits on it.