Oh toad, lets hope there's some thread sticking out to grap on to. Of course there wasn't.It was a m6 bolt and the best drill bit I had was probably a 4mm Ti or HSS. After what seemed like an hour of drilling, all I had managed to achieve was a nice smooth Indent in the bolt.
At this point I gave up, concentrated on getting through my exams for the next couple of weeks, and finally got to tackling the bolt again today.
Rather than working hard, I thought about working smart for a change. I bought a 2mm and 3mm cobalt drill bit (expensive, but worth every penny) and some 3-in-one oil. The result was drilling through about 2cm of stainless steel in a minute or so, I couldn't belive it!
Just use a center punch to dent the center of the bolt, apply the oil to to drill bit and bolt then drill away. Use a low speed with a little bit of force.
I then tried using the 'easy' out to extract the bolt, but it didn't bite and just blunted (probably because it was so hard to get in in the first place). I was also told that if the easy out breaks in the bolt it will be nigh impossible to drill and make your life 10x worse.
My dad then said to try hammering in an oversized torx bit. Sure enough, it worked!
After that I just re-tapped the hole and was good to go. I hope this will save some of the useual :smt013 when doing this sort of job, it certainly did for me.