Originally Posted by
RichR
Depends on what the drill bits were made off. If they're fairly cheap HSS ones, you may well be able to drill them out with cobalt drill bits. I have successfully done this a few times.
If you do decide to lash out on expensive bits to drill out the cheap ones, make sure you run them at the correct speed (generally a lot slower than you think), with adequate lubrication and ideally in a drill press rather than hand held. Saves you swearing when you break one....
Don't forget to weigh up the cost of getting the broken bolt out of a component against what a second hand component would cost. It might be cheaper and easier just to take an angle grinder to the offending item and replace it.