Sheared Exhaust bolt....

[txironhead]

The only other option that I can think of is a tungsten bit in a Dremel or drill. With a small enough bit you might be able to eat out the middle of the ez-out.

[t3rmin]

Regarding the use of the cobalt bits to drill out hardened metal: I think you want to use a lower speed and lots of pressure, rather than high speed. Also make sure you don't allow the bit to get too hot (take breaks). It will sometimes take a few bits to get through a lot of hardened metal, but it's very doable.

[spchips]

I second the low speed on the cobalt bit. also, use a larger one that can take big bites.

I saw these diamond powder coated abrasive bits at the dollar store once. never tried them though...

I got a tap out the other day with a cobalt bit and beating the ##&$% out of the thing it get it to fall through the hole. of course, there is no hole in your case.

[twistedwankel]

So I tried the cobalt drill bits, and they still were quickly dulled by the hard tool steel EZ-outs. Heating the head or the block, or iserting penetrating oil or candle wax is all great ideas, the problem is, that I have no bolt left to grab ahold of with vice grips or anything. The bolt is sheared basiclly flush with the engine block head. As anyone heard of EZ-out extractors?? A tool designed to remove broken EZ-outs?
I looks I need to go to a machine shop, or replace the head. Removing the head from the engine might not be a bad idea anyway, that way I can check all the valve shims and spacing while I am in there.

Okay. Here's another way around the beast.
I used a small drill and put holes around the broken extractor so then there was a spot to prick punch it backwards and also took the stress (grip) off the easyout that was binding it in there. Tighter than a honey moon prick I bet.

Even when I don't have anything but a sheared bolt I always use a pilot hole thru the broken bolt first. Then having established the length of the bolt I drill and tap the hole.

The "studs" are a great suggestion but they are slightly expensive and once you put never seize on a SS or non rusting bolt you shouldn't have a problem ever again. The true advantage is they make a stud with different size threads just in case you have to oversize the original hole

[gotjeepzj]

I used an 8mm socket from a cheap set, hammered it on and it backed right out:-D

[duaneage]

The "studs" are a great suggestion but they are slightly expensive and once you put never seize on a SS or non rusting bolt you shouldn't have a problem ever again. The true advantage is they make a stud with different size threads just in case you have to oversize the original hole

They are NOT too expensive, compared to the hassle of breaking off a bolt. never seize might work but you still have aluminum and steel there. Studding the bolts puts a steel nut on a steel bolt and that's worth it.

As to removing the easy out, Dremel tool with carbide bit will do it. Take your time with it. Easy out is an oxymoron if there ever was one.