Posted by David Sherman on Sunday, February 12, 2006 at 1:12PM :
In Reply to: Re: Advice re broken head bolt posted by David on Sunday, February 12, 2006 at 1:00AM :
If you are forced to try to drill it out, it is vital to have the hold absolutely centered, use a perfectly sharp high-quality drill, and put some cutting oil on it if you want it to stay sharp. Head bolts and studs are hardened steel and will eat cheap drill bits for lunch. The centering is vital because the bolt is much harder than the cast iron, and if the bit starts to bite even slightly into the cast iron, it will immediately head for the cast iron and then you'll have a ruined block as well. Watch it closely, and stop as soon as it starts to wander. If there's a enough bolt sticking up to put a torch on, that's another reason to heat it red hot and let it cool before starting your removal procedure -- the heat will soften the bolt so the drill will have an easier time of it.