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.

[rick 918-S]

OK, I did some deep thinking about this today. Unfortunately, I didn't have the light bulb moment until most places closed for the day.

Here's how I'm going to fix this. If it works I'll post pics.

I located left hand drill bits on http://www.mcmaster.com/

They also have left hand taps and bolts!

I'm going to machine a drill bushing that doubles as a chuck for a (short) left had drill bit. Sometimes during the drilling the threads will back out. If it doesn't,,,,,

I am going to use the left hand tap to cut threads in the pilot hole.

This sometimes will cause the threaded section to back out. If it doesn't,,,,

I am going to thread in a left hand grade 8 bolt. This will repair the broken bolt and give me a positive bite on the threaded section. If the bolt breaks I can just drill it again.

If I used an extractor and it breaks, I toss the block in the scrap pile.

Extractors = bad.... (IMG:style_emoticons/default/dry.gif) bolt = good... (IMG:style_emoticons/default/biggrin.gif)