<VV> Broken bolt in crank... UPDATE!

[Bill Elliott]

Thanks for everyone's on and offlist advice...including from Larry Claypool.

Here's what I did...

I started with a pair of large vicegrips.. no joy... bolt was in there 
tight!

Next, I pulled out my MIG welder (which I had bought used on Ebay months 
ago and had never used... with no real welding experience to draw on), 
got it set up and working and did a couple test welds on a scrap piece 
of metal. No real skill, but at least I could do a real nasty weld.

So I pulled out a 3/8 nut, threaded it on, tried to weld down through 
the bolt to the stud... and the nut broke off the moment I took a wrench 
to it.

So on further advice (for people that REALLY can't weld) I fit a 3/8 
washer over the bolt and welded it all around. This is much easier for 
someone with no skill than trying to weld on the inside of a 3/8 nut... 
then I fit another 3/8 nut, welded inside again... AND outside to the 
washer... getting the nut red hot. (I was told the other benefit of the 
washer was to protect the crank surface from the additional heat...). I 
let it cool for about 3 minutes, then the stud backed out like it was 
only in hand-tight. Beautiful.

I then broke out my new 11/32-24 tap ($10.50 from 

http://www.victornet.com

...but with a $25 minimum order)

and chased the threads. ALL of the threads were much dirtier than I had thought...they should all have been chased to start with... and amazingly, the hole where I thought the bolt was crossthreaded cleaned out nearly as well as the other holes with very very little thread material removed by the tap.  The bolts test fit by hand all the way through in 4 of the holes... and all the way to the last couple of threads on two holes (including the one where the bolt was stuck). The tap's pointed end is just a bit too long (hitting the gear behind) to fully clean all the threads. Since this is my only application for this tap,  I may try to grind 1/8" off the tip...that may be enough to just get those last few threads clean and straight.

Lessons learned?

1. Chase all threads and carefully examine all critical hardware before use.
2. STOP when something doesn't feel right...trust your instincts
3. That cheap welder (Lincoln 110v 100 Weld-Pac... $125) was a REALLY good buy. (Now to just learn to use it...)
4. Come to VV after you really screw up and get good guidance on how to dig yourself out.

Now just awaiting new bolts from Larry http://www.vairshop.com/ (have to get a plug in there for him!) and I'll recommence assembly...

Thanks again guys!
Bill


>
> Bill Elliott wrote:
>
>> Always go with your first instinct... as I was mounting the flywheel 
>> on the engine I'm assembling, one of those special 11/32 bolts didn't 
>> seem to want to go in right. I normally chase all threads when 
>> assembling, but I didn't have one of the unusual size taps. The 
>> threads on both hole and bolt looked okay and on like the third try 
>> it seemed to go in easier (but still a bit tight for my comfort). I 
>> should have stopped at that point... but I didn't.
>>
>> As I was torquing down the bolts, the head on this one popped off. 
>> Now that I have disassembled everything again and examined the 
>> situation more closely, it appears that the bolt is slightly 
>> cross-threaded in the crank AND shows evidence of having been 
>> "attacked" by an impact tool sometime in it's history...
>>
>> Now in 20 years of working on Corvairs I've never seen this problem 
>> before. I do have almost 1/4" of the broken bolt protruding, but it 
>> is in _tight_.
>>
>> Any advice on how to best extract it without damaging my crank?
>>
>> Also, assuming that I have permanently damaged the threads (I did 
>> just find and order the correct tap) what is anyone's experience in 
>> drilling and retapping to 3/8-24?
>>
>> It's bad enough when major problems happen, but it's even worse when 
>> they were clearly preventable with a bit more care...
>>
>> Thanks!
>> Bill
>>
>>
>
>


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