Drilling out a bolt

[Talonmotorsport]

All though drills used on steel are called HSS (high speed steel) they need to be run at a lower speeds rather than flat out and used with a cutting paste/oil such as ct90. A problem that you may now have is as the bolt gets heated by the head and now the drill bit it may have become hardened which will make the job nigh on impossible to drill in to.