Removing bottomed out bolt with broken head

[promethean-in-fl]

If it was broken off flush a machine shop might be a good choice. I recently watched a video (machine shop) where he demonstrated removing a flush bolt. He used a endmill to make the broken bolt flat then drilled the center of the bolt out. The drill bit was the same size as the root of the bolt thread. If done in the center of the broken bolt it will leave only the thread which can be fished out using a pick. He got the complete thread out in one piece, looked like a thread repair insert when out. The PO's situation, I would use vise grips first, then weld a nut if the VG didn't work.

Did they use a right hand or left hand drill bit?

 

[dogdog]

Oxtools Co have a 2 or 3 video series on stuck nut/bolts removal everything from mildly seized to broken taps/drill bits stuck, if that is what your interests are. Just google for it. The video is at least 3 to 5 years old by now, but still good info. Everything you would have needed from a machinist stand point,"if" you have the equipment. or look up the guy that uses EDM.


Me at home, with 3 of the 6 exhaust down pipe studs broken, but still grab with a vise grip... I just used a propane torch or propane/oxygen small ones and heat it as dull red as I could. after a few cycles it came right out. Now a days I bought the induction heater. (MD-710).. that worked in many situations but not all... I think your case you did not heat it hot enough... 190F is simply not enough for stuck exhaust bolts/nuts/studs.