Anyone ever break a head stud?, Looking for ideas, tools success stories, horror stories, what cha got Options

[rick 918-S]

I'm building a 928 hybrid engine which is comprised of a 5.0L 32 valve short block with 16 valve euro spec "S" heads, spyder and CIS from the 4.7L "S" engine.

I stole some time from my busy work schedule to prep my 928 block for the machine shop. The head studs need to be removed for the boring process.

Now I've pulled studs before without incedent. But as Murphy would have it, this time I broke one of the studs flush at the start of the threads.

So I have the threaded section ( 1 1/4"long ) hardened head bolt stuck in the block. Normally this wouldn't be a problem, but the stud is free standing in a 3 1/2" deep hole in the block!

Here's a crude drawing of the problem I'm faced with.



Here's the stud.



Here's the stark reality of the stud in and out of the block. The stud slides down a 3 1/2" deep hole in the block before it starts to thread in.




I'm going to make a drill collet as a guide for a pilot bit. The problem is I need a long, reverse twist drill bit.

Most drill bits are approx 5" long. the hole is 3 1/2", the threaded section is 1 1/4" for a total of 4 3/4". See the problem?

Then, what the #$!! do you drill a hardened bolt with?

Anyone know of a good tool source? This is beyond most Mac and Snap on stuff I would think.

[Katmanken]

Aircraft work sometimes requires extra long drill bits- say 12 inches or so......

These are not reverse twist but they might be a workaround and the prices aren't too bad.....

Aircraft 12 inch long drills linky link

I do like the guide pilot idea if the bore isn't tapered.

Ken