Help: Broke off endpin screw

Discussion in 'Luthier's Guitar & Bass Technical Discussion' started by JimVW, Feb 28, 2006.


  1. JimVW

    JimVW Member

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    I was installing strap locks on my Tokai ES-100 and I didn't read the directions where they said to rub soap on the screw before tightening. I don't think I was using excessive force, but the screw head snapped off, slightly below the surface.

    I tried drilling it out, but I was hardly making a dent with what I thought was a fairly sharp bit.

    How do I get that old screw out of there? Do I need to get a higher quality bit?
     
  2. Diablo

    Diablo Member

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    You will probably need a carbide drill bit to drill a broken screw out. A dremel can work good too. You need to get it flat or else the drill will walk off of the screw and go for the softer wood. Another thing that you can do is to get enough clearance around the screw so that you can get some needle nose vise grips on it. Yet another thing is to use a dremel with a small router or grinding bit and clear it enough to get the vise grips on it.
    Also, you can go to home depot and get a plug cutter. That's a bit that goes in a drill and is hollow. It cuts out dowel type plugs. The screw shaft will be in the plug that it cuts out. Then you fill the hole with the correct sized dowel, dye it and the strap button covers it up.
    You can probably get it out with some grinding and vise grips. It is really hard to drill a small screw out with a drill. You might want to try using a centering drill first. That's a short, thick shafted drill with about 1/8" of drill bit. That way, you can get a start hole for your drill bit. You might have to get those at an industrial tool place.

    With a little bit of work, you can probably get it drilled out without much problem. In fact, if you can get it started with a centering drill, you can probably do it. It just depends on what the screw is made of. That will tell you if you need carbide or not. Also, don't let the drill spin fast or it will destroy the drill bit.

    One thing that I've done in this situation is to use a diamond grinding burr. Dental ones. You can probably get one from a dentist if you know one. (Since this is a PRS type forum, and we all know that only doctors and dentists play PRS, you shouldn't have any trouble finding one.:D)This works really nice because the burr is tiny, about 1/16" diameter. That way, it just grinds the screw out with relatively no damage to the surrounding wood. Hope this isn't too confusing or intimidating. Good luck.
     
  3. Chiba

    Chiba Gold Supporting Member

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    Last time that happened to me, it happened about 1/4" inside the guitar.

    I got a very narrow-bladed flat-head screwdriver and hammered it on in there until it created a slot in the broken screw, then I just backed it out slowly.

    Not really recommending that, just saying ... if Joe's method doesn't work for you, all hope is not lost :)

    --chiba (non-dr, non-dentist, non-lawyer but plays 2 PRS guitars :dude)
     
  4. John Phillips

    John Phillips Member

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    Chiba's method can work, but probably not on a hardened screw, which that sounds like.

    This is a nasty problem... luckily it's a strap button so you can risk a small amount of damage to the surrounding wood without it showing once it's fixed (although Gibson-style buttons don't leave much room).

    One trick I sometimes use if the screw isn't too deeply buried is to heat it with a soldering iron - you'll need a little fresh solder to make a good thermal contact. This will expand the screw and dry the wood slightly, making it shrink, so it grips the screw less, then as the screw cools it may come loose. After a few hot/cold cycles you should be able to free it with a pair of needle-nose pliers. You may burn the wood slightly and chew it up a bit with the pliers, but if you're careful it shouldn't be outside the footprint of the button, and you can patch the oversized hole with a dowel if you have to. A plug-cutter is possibly safer, but then you definitely have to dowel - at least if you free the screw with heat you can usually get another one into the same hole. Not a big difference overall though.

    The one thing NOT to do is to give up and fit a new button half an inch away :).
     
  5. JimVW

    JimVW Member

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    Thanks for all the great input. I'll start with the least destructive method first and go from there.
     
  6. Brion

    Brion Supporting Member

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    Try a small screw extracter bit and drill it out. That's what they're made for.
     
  7. hogy

    hogy Member

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    That is the correct basic idea, however it will leave a huge hole as those dowel cutters are pretty thick walled.

    Here what you do, it's easy.
    Go to a hardware store and buy a piece of thin walled brass tubing with an inside diameter the same as the outside diameter of the broken screw. If the hwstore doesn't have it you can get it at a hobby store that sells model plane stuff.

    Cut a 3" piece off of it.

    With a small triangular file, cut "teeth" into one end of the tube.

    Put the piece in a drill and REVERSE drill over the screw shaft. The tube will cut the wood around the screw while being guided by it so you can't slip or misalign.

    Once you get to close to the end of the screw it will get stuck inside the brass tube and come out with it. Throw the tool away.

    The resulting hole will only be slightly bigger than original and can easily be doweled.

    This is fool proof and works like a charm. I've done it hundreds of times in my repair business.
    Don't even try to drill into the screw, the bit will slip off and chew up the wood.

    Hogy
     
  8. LHanson

    LHanson Member

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    Genius!
     
  9. John_M

    John_M Supporting Member

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    That is cool!

    Or you could do what I do - get a new screw, drill a pilot hole next to the old one and put the button right next to the old screw. Most of the time it covers the old one anyway.

    Plus, you're adding mass to the guitar with the extra screw in there, which helps the tone :)
     
  10. ronin32

    ronin32 Member

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    You can also try cutting a small slot in the broken screw like a new flat head screw. I use to race rc cars and this would happen a lot but with titanium screws and their heads would shear off. I would use a Dremel tool with a engraving type tip so that its small enough to get into the hole and cut the screw, then just back it out.
     
  11. JimVW

    JimVW Member

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    Well, I've tried a lot of these suggestions, but I'm not having much luck. I think the main problem is that it's a hardened screw, so just about everything I'm trying won't cut it.

    I eventually got around to Hogy's idea, but had trouble finding the brass tubing. I finally got some over the weekend, and it worked like a charm until the top 1/4" of the brass tube broke off inside the hole. If I can get that out of there, I think I could finish it up. Any ideas on how to remove it??
     
  12. John Phillips

    John Phillips Member

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    Did you try heating it? The brass should make a better thermal contact now too... then you might be able to get some very fine needle-nosed pliers onto it.

    I think you may have to accept some wood damage, but if you're careful it should be under the area covered by the button.
     
  13. JimVW

    JimVW Member

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    Finally got it out last night!!

    What I ended up having to do was dremel around the screw to widen the hole at the top, and then use a 1/4" plug cutter, which fit around both the screw and the broken off brass sleeve. Once I got it deep enough, I was able to use needle-nose pliers to back the screw out of the remaining plug of wood, then I used a 3/8" forstner bit to clean out the hole completely.

    I bought a 3/8" dowel over my lunch break, so I should be in business tonight!

    Thanks again, everyone, for your help.
     

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