Before you damage that bolt any further and need to look at drilling the bolt out, bolt extraction kits, helicoils and so on, here’s a couple of really quick tips on how to loosen those stuck bolts.
1. Loosen the stuck bolt with a blowtorch
Yep, you didn’t misread that. Grab a blow torch and steadily heat evenly around the bolt head, nut and anything you can get at around the thread. This allows the metal to expand as well as burn off any crud. You don’t need to heat it until it’s white hot, just a couple of minutes.
Then attempt it again, if it’s something like and exhaust stud then get a set of mole grips/ locking jaw pliers on it and try those, if there’s no movement try the blow torch a couple of times again. Most of the time this will loosen that pesky frozen bolt.
And if there’s still no movement…
2. Use an impact driver to free the stuck bolt
These are great and for a few quid you can get one that you just hammer in manually and most of the time this will loosen it, the force from the hammer drives whatever you have connected to it into the screw/bolt and also translates that energy into rotational movement to ensure maximum grip and force on the bolt. Although sometimes this can remove the head off the bolt – but then you’d end up drilling the bolt out anyway so it’s no real loss. If you’re lazy you can also get electrical/ cordless impact drivers or ones that run of a compressor, but alas I am cheap and have no ready supply of electricity from which to run one.
3. Take a hammer to the frozen bolt
Again sounds unlikey but if you have a crosshead screw for example – get an old screw bit or screwdriver and hammer that into the head until it feels like it’s got some purchase and very slowly try to turn it. Don’t apply a lot of force, just enough to test it. If it’s a hex bit, get a star/torX and hammer that it, using just a slightly bigger bit, hammer that it. If it feels like you’ve got a good purchase then attach the breaker bar/ sliding T bar and apply some force – after all the heating etc… this should budge.
And if that all failed then it’s time to drill it out.