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.

[Dr Evil]

Well?

[rick 918-S]

Well?

I can't get a break! I drilled the broken bolt perfect, I tapped the threads perfect, I threaded the cap head in perfect but the allen stripped. I pounded in a metric size allen wrench and removed the cap head bolt. I tried a second bolt but even with super heating the block I couldn't apply enough torque to the cap head to move the stud. Size does matter. I probably needed to move up to the next size drill and tap. I could literally twist the allen 1/8 turn without phasing the broken bolt. I tried to use the tap as an extractor as it was less likely to loose power in the flex the allen wrench was showing. But as luck would have it, just as I thought I felt the bolt move, SNAP! the tap shattered!

I'm going to try that welding idea now. I've got nothing to loose. (IMG:style_emoticons/default/headbang.gif)

[Wilhelm]

Well?

I can't get a break! I drilled the broken bolt perfect, I tapped the threads perfect, I threaded the cap head in perfect but the allen stripped. I pounded in a metric size allen wrench and removed the cap head bolt. I tried a second bolt but even with super heating the block I couldn't apply enough torque to the cap head to move the stud. Size does matter. I probably needed to move up to the next size drill and tap. I could literally twist the allen 1/8 turn without phasing the broken bolt. I tried to use the tap as an extractor as it was less likely to loose power in the flex the allen wrench was showing. But as luck would have it, just as I thought I felt the bolt move, SNAP! the tap shattered!

I'm going to try that welding idea now. I've got nothing to loose. (IMG:style_emoticons/default/headbang.gif)

If the weld ing idea doesn't work, or as an alternative, can the stud be addressed from the bottom? If there is more access to drill it out from the bottom, or oversize drill it out, maybe the block can be tig welded to seal up the hole that is made. Have you let a machinist take a look at the block? Some are actually purty sharp and can devise alternative methods to get these studs out. Also if hour drill hole is "perfect" you might want to keep drilling it till it is t the base of the threads, then pick the threads out. Though I suspect this would be awful tricky deep down a hole.