Best way to remove tricky broken bolt?

[Fredrik1]

I use an automotive air hammer, and trust me, it has saved me on lots of stuff. works like magic. Mike.

Great! I've never tried this. Left drill bits ordered. Then I'll give this a try, following some on/off w a torch. BR, //Fredrik

[44DHR]

Just picking up on Stuart’s post #10 regarding expansion/contraction, another good “tool” to free stuck rusted items is the “Crack-it” freeze spray which works by shock freezing the items. It also contains a powerful penetrating oil which literally can be heard to crack the seized item’s joint.
There also have been comments about the suitability of WD-40 regarding its penetrating oil ability. I agree with that comment on the “normal” WD-40, but that brand also produces several “Specialist” products - one of which is a fast release penetrant.
I have no allegiance to either, other than being a satisfied user.
Cheers,
Dave

[Jack the lad]

I had a similar problem on a brake calliper bleed nipple which was broken by a previous owner. It was a very small nipple thread and in a difficult position to drill. I found a spark erosion company nearby in Yellow Pages, they did it for me while I went for a walk around the shops and 2 hours later it was ready for collection. It was a perfect job and only cost £20. A replacement calliper was £750 (Maserati), no exchange allowed if old calliper is anything other than perfect! The thread was perfect and did not need any cleaning up at all.

[Fredrik1]

I use an automotive air hammer, and trust me, it has saved me on lots of stuff. works like magic. Mike.

...and the winner is: Autoalain! Many thanks, the vibrations really made the difference. I went overboard and used an air chisel hammer where I blunted one of the tools. As soon as I stopped, the bolts went dead again. This is with heat and proper rust penetrating oil applied over a few days.
Cheers! Happy New Year to you all! May your 2023 be as good as my 2022 just got!

[tim wood]

Excellent news, persistent pays !


Onwards and upwards

[mgman]

Good that the stud was removed
A method I have successfully used is putting a nut over the stub and with an arc welder set highish push the rod down the centre. This has a twofold effect of giving you something to get hold of and getting the shaft extremely hot. This works on cast iron where direct heating is ill advised.