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How to repair stripped thread on wood screw hole?

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How to repair stripped thread on wood screw hole?

Postby Jathon Delsy » Sun Nov 26, 2017 10:31 pm

One of the little screws that holds the plastic backplate on is really loose because of what appears to be the thread in the hole being stripped. Does anyone know how to repair this, preferably with a solution that enables me to repeatedly remove and retighten the screw, as I often need to open the back to adjust the whammy springs.
Thanks,
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Re: How to repair stripped thread on wood screw hole?

Postby Sam Spoons » Sun Nov 26, 2017 10:38 pm

The simplest way is to plug the existing hole with a matchstick (glue it in with PVA wood glue and break or cut it off flush) then refit the screw.
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Re: How to repair stripped thread on wood screw hole?

Postby Wonks » Sun Nov 26, 2017 11:06 pm

I prefer to use a cocktail stick as the wood is harder, but the principle is the same.

I normally trim the end with a pair of electrical wire cutters, let the glue dry for at least 12 hours, then cut the end off flush with the body using a really sharp blade - scalpel, single edge razor blade or Stanley Knife blade.
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Re: How to repair stripped thread on wood screw hole?

Postby zenguitar » Mon Nov 27, 2017 1:18 am

Almost exactly the same as Wonks but with one variation. find some slightly fatter hardwood cocktail sticks that are just bigger than the screw hole and a matching drill bit that makes a good friction fit hole for them. Then carefully drill out the old screw hole and fill as Wonks described.

Two reasons for that. The first is that you remove the old threads and get a solid wood/wood glue join. And the second is that the old fashion and correct way to fit any wood screw is to put a little candle wax on the thread before screwing it in. The way a screw works is by stretching with the final 1/4 turn, that means that it is trying to reurn to normal length and in doing so pulls the 2 parts together, and in turn this creates a friction joint between the 2 parts. If it isn't lubricated you run the risk of the friction of screwing it in compressing the screw so it doesn't stretch with the final 1/4 turn, and in turn that means you have to over-tighten the screw. This over-tightening and the associated friction is (in the worst case) the cause of heads breaking off screws when trying to remove them, and also damaging the slots so that the screw driver slips out. That's why the tool boxes of any woodworker of my grandfather's generation or competent DIYer of my father's generation always had a candle stub or two. Comes in really handy for waxing screw threads, the soles of planes and many other things.

Not everyone waxes screw threads these days, but there are still plenty of people like me who do. So drilling out stripped threads removes any remaining candle wax left behind by someone like me. The other great thing about waxing screw threads and using the correct size screwdriver is that you are far less likely to get stripped threads in future :)

Andy :beamup:
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Re: How to repair stripped thread on wood screw hole?

Postby Watchmaker » Mon Nov 27, 2017 5:37 am

To add to zenguitar's excellent post, wax residue may also interfere with glue adhesion making the repair too weak to hold thread tension.

All good tips.
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Re: How to repair stripped thread on wood screw hole?

Postby ef37a » Mon Nov 27, 2017 11:11 am

The technique is called 'dowelling' and the above advice is fine for small holes and low strength items.

If you need to repair a bigger hole, 6mm or above then the size of the dowel becomes more critical. Too small and it obviously will do a poor job. To fat and there is a danger of splitting the surrounding timber.
There is another dodge for big dowels. Cut a slot with saw along the length of the dowel, 1mm deep is fine. This allows the glue to flow better and ooze out of the joint allowing the dowel to 'get home' better and stops the risk of the hydraulic pressure also splitting the wood.

For REALLY strong jobs you want the grain of the dowel ACROSS the screw thread not with it. You can buy special core cutters to make these but you really need a drill press for that.

There are also 'contra-threaded' brass bushes that you can use, best set in epoxy.

Dad was foreman in an organ builders woodshop. I learned a FEW things from him!

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Re: How to repair stripped thread on wood screw hole?

Postby gnappi » Wed Dec 20, 2017 11:15 am

All the above suggestions are good, but the back plate of a git doesn't present any stress to the screws holding it in. A simple fix is a toothpick pushed into the hole with a dab of wood glue on it, then broken off at the top / back of the body and left to dry. I have found this is pretty permanent.
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Re: How to repair stripped thread on wood screw hole?

Postby Martin Walker » Wed Dec 20, 2017 4:33 pm

gnappi wrote:A simple fix is a toothpick pushed into the hole with a dab of wood glue on it, then broken off at the top / back of the body and left to dry. I have found this is pretty permanent.

I've often used a similar approach, but with a matchstick. Toothpicks use harder wood that will probably be longer-lasting for guitar use, but matchsticks work very well to pad out rawlplugs when attaching things to a dodgy holes in a wall ;)


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Re: How to repair stripped thread on wood screw hole?

Postby BigRedX » Wed Dec 20, 2017 4:35 pm

If you are going to need to be removing this back plate with some frequency, I would suggest replacing the wood screws with small bolts and threaded inserts.

Alternatively hold the panel in place with a few small neodymium magnets.
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Re: How to repair stripped thread on wood screw hole?

Postby Wonks » Wed Dec 20, 2017 5:46 pm

Or cut some holes in the back of the plate so you can access the screws without taking the plate off. I know some Fret King guitars have such holes as standard, and Ibanez often have access holes in the back plate as well.
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Re: How to repair stripped thread on wood screw hole?

Postby gingertimmins » Wed Dec 20, 2017 10:47 pm

If it's a strat type geetar then why not leave the back plate off? There are even claims that thus increases sustain.
Pretty sure the sustain bit is bollarks but I've had no issues without a backplate for years.
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Re: How to repair stripped thread on wood screw hole?

Postby Sam Spoons » Wed Dec 20, 2017 11:03 pm

I can;t be sure, I have two Strats both sans back plates and for years have been finding mysterious small holes in the front of my tee shirts (much to my wife's chagrin). At first I thought they were due to the trem springs, later to the damaged neck bolts, still don't know what causes it and still without back plates :D
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Re: How to repair stripped thread on wood screw hole?

Postby Wonks » Wed Dec 20, 2017 11:09 pm

Do you have a resident sniper at your gigs?
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Re: How to repair stripped thread on wood screw hole?

Postby Random Guitarist » Thu Dec 21, 2017 1:13 am

The thing I like to do do in conjunction with the match stick repair is have plenty of glue in the hole and put the screw in while the glue is still very soft. It seems to me the glue then softens the wood fibres when the screw goes in so they conform better to the thread of the screw., and once hardened the glue reinforces the shape of the thread in the wood.

The next time the screw is removed there is a definite moment as the small bond between screw and wood glue breaks, but screwing it back in there is a very positive thread engagement.

Well, it seems to work for me anyway.
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Re: How to repair stripped thread on wood screw hole?

Postby Martin Walker » Fri Dec 22, 2017 12:52 am

Random Guitarist wrote:The thing I like to do do in conjunction with the match stick repair is have plenty of glue in the hole and put the screw in while the glue is still very soft. It seems to me the glue then softens the wood fibres when the screw goes in so they conform better to the thread of the screw., and once hardened the glue reinforces the shape of the thread in the wood.

I LIKE that :thumbup:

Good idea Random Guitarist 8-)


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Re: How to repair stripped thread on wood screw hole?

Postby ef37a » Fri Dec 22, 2017 8:08 am

Martin Walker wrote:
Random Guitarist wrote:The thing I like to do do in conjunction with the match stick repair is have plenty of glue in the hole and put the screw in while the glue is still very soft. It seems to me the glue then softens the wood fibres when the screw goes in so they conform better to the thread of the screw., and once hardened the glue reinforces the shape of the thread in the wood.

I LIKE that :thumbup:

Good idea Random Guitarist 8-)


Martin

Agreed but, coat the thread with soap or some other grease. If the screw properly sticks to the glue you could turn the head off trying to remove it, especially a danger with plated brass screws.

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