How to fix sheared screws in headstock?

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How to fix sheared screws in headstock?

Postby Adam Savage » Tue Apr 23, 2013 5:08 pm

Greetings,
Yet again I have a question for the forum. I have nearly finished my second build (only the electrics and strings to put in, though being a hollow body the electrics might take a little longer), and was screwing in the locating screws for the tuners. Unfortunately I managed to shear two of the screws, leaving a stub of screw in the headstock. A combination of reasons :
1) not drilling the pilot holes deep enough (silly mistake)
2) not taking account of the rosewoods' density (experience)
3) doing this after 12 hr night shift (idiotic mistake)

Anyway, I imagine there are 3 solutions :
1) use a makeshift drilling jig to drill out, oversize, the screw stub. Then pack hole with rosewood plug or 'matchsticks' and re-drill pilot hole.
2) leave alone and use a little epoxy to fix the tuner in place
3) replace tuners with another model that has the locating pin in a different place. The originals are gotohs and I do have a set of sperzels that are nearly the same colour (matt black vs black chrome of the Gotoh). This would work, but there is a slight aesthetic issue and I need to check that the holes are appropriate diameter for the Sperzels.

So, what are your thoughts? Any other options I haven't thought of? Any particular concerns with either of the solutions above?
Once gain, I appreciate your advice,
Adam
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Re: How to fix sheared screws in headstock?

Postby Mark Swanson » Tue Apr 23, 2013 5:14 pm

If you take a small piece of metal tubing that will fit around the screw, then you can file teeth into the end of it. Put it in your drill press, and use it to drill around the screw. This will allow you to get the screw out and glue in a matching piece of wood.
    Mark Swanson, guitarist, MIMForum Staff
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Re: How to fix sheared screws in headstock?

Postby G.S. Monroe » Tue Apr 23, 2013 5:21 pm

The last time this happened to me, I took my dremil cut off wheel and cut a slot into the screw stub. This only left a narrow cut in the wood but allowed me to back the screw out with a small slot head screwdriver. The narrow cut is much easier to repair than filling an oversize hole.
I tapped in a thin veneer shim to fill the slot and then CA+'ed the area to fill the remaining gaps. I re-drilled the pilot hole and inserted a fresh screw.
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Re: How to fix sheared screws in headstock?

Postby David King » Tue Apr 23, 2013 5:50 pm

I would try a hot soldering iron to heat up the screw and char the wood around the screw. You need a bit of solder on the iron's tip to help the heat transfer into the screw. Let it smoke for a minute or two and try wiggling the screw too see if it loosens up at all. if you can jiggle it you can back it out using the dremel trick (Use a small, worn down disk to minimize damage to the surrounding wood.)
I have a lathe and I've made the screw extractor tubes from oil hardening drill rod. The teeth are harder to file than you would think. They also tend to flare out as soon as they hit the wood and that makes a mess. This is probably because I didn't clear the chips every few seconds and that caused the metal to overheat. Some combination of the three techniques may be necessary.
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Re: How to fix sheared screws in headstock?

Postby Adam Savage » Tue Apr 23, 2013 7:28 pm

Thanks for the suggestions folks. I shall try the Dremel trick first as that seems the least invasive. The screws have maybe 2-3mm at most threaded in the headstock, so hopefully that will work. I don't have any direct replacement screws, and the ones I do have are a little wider anyway, so I may even get away without filling the leftover-hole.
Cheers,
Adam
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Re: How to fix sheared screws in headstock?

Postby Adam Savage » Wed Apr 24, 2013 5:31 pm

Following the suggestions above, I attempted a fix this morning. Initially trialling a cutter wheel on my dremel, I found that the screws were either too small to retain a slot or my control of the tool wasn't good enough. Instead I used a very small burr tool to excavate around the screw stubs. This was relatively slow, but resulted in a neat hole that I then filled with sawdust and epoxy mix. A quick sand once cured, and a first coat of tru oil is now drying.
Possibly not the greatest cosmetic fix, but one that I am happy with to be on the reverse off the headstock.
I shall post a couple of photos along with the rest of the build once completed.
Cheers,
Adam
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