On Dec 30, 2:39*pm, komobu wrote:
Hi;

Often I need to extract broken bolts / screws and am thinking about
picking up some left handed drill bits. Usually I have to extract
broken steel bolts and screws from aluminum heads and manifolds. Most
often they are broke off clean and need to be drilled. When looking at
drill bits to purchase, *I see they are made of HSS, Cobalt and
Titanium. What drill bit material is the best for staying sharp and
long lasting life?

Also, please comment on grabit and other extracting methods. What do
you think is the easiest way to remove a broken bolt?

Thanks for any advice
Pat

Cobalt is a step up from regular HSS. Titanium is actually titanium
nitride, TiN, which is just a coating. It's the steel underneath that
is important.

Lots of ways to remove broken studs and screws without welding.

You're on the right track with the LH drills.

I've had fairly good luck with Easy-Outs. The trick is to use the
right size. Too small and it will snap. Too large and the remaining
screw will be thin enough that the Easy-Out will expand it.

Kroil, PB Blaster and the other penetrants are a must.

A hot alum solution will dissolve a steel screw without hurting the
aluminum head. Eventually. It works better on taps, because the
flutes allow it to work on the threads.

EDM is great if you can get the part to a shop that has the equipment.

John Martin