Extracting broken wood screws

[Hörnisse]

Anyone have suggestions?  2 out of the 3 bridge screws for a guitar I picked up recently are broken off at the head.  They are the screws that attach the bridge plate to the guitar.  They seem to be brass screws if that makes a difference.  I've heard that extractors don't work well.  Just looking to the experts for some advice.  Thanks!

[Lightyear]

Any of the shaft left exposed above the surface of the body?  If so I've had pretty good luck with needle nosed Vicegrips ground flat on one side the jaws allowing contact with the body with maximum grip.  If they are typical #6 screws and they're flush I don't know of an extractor that will work on something that small - you may have to surgically chisel out some wood allowing clearance for a tool to get to them.  If you're careful you can glue the piece(s) back into place.

[Hörnisse]

Unfortunately they are about 1/8 inch into the wood.  I guess since it will be hidden under the bridge plate I should not worry too much about cosmetics. 

[Lightyear]

If they're that deep, and they're under the plate, I would be tempted just to drill an new pilot hole right next to the broken ones.  I would would sacrifice a few screws to "tap" the threads for the final screw.  I would lube the screws with something and run them in carefully and slowly.

[Pilgrim]

Here's a technique I've heard of on TB.

Get some brass tubing with interior diameter just larger than the remaining shaft of the screw.  You are going to make a hole saw with it, and remove a plug of wood with the screw shaft in it.

Cut about a 2" long piece of this brass tubing, then file V-shaped teeth into one end. This creates a very small diameter hole saw.

Chuck the tubing up in your drill, set the end of the tubing over the shaft of the screw, and start drilling slowly, my guess is that you'd want to do it in reverse.

You may grab the screw and back it out, but more likely you will drill out a plug of wood with the screw shaft in it.

You then can craft a plug to glue into the hole, then cut the plug off level with the surface of the body.  This will give you something to screw into.  It may require refinishing if the screw is not covered by some part of the instrument.

I have read multiple reports of success with this approach.  It's often used on bridge mounting screws or tuner screws. It does require plugging the hole, but that's MUCH cleaner and will impact less surface area than digging or chiseling out the screw shaft.

[Highlander]

No THAT is a great idea...

[Denis]

Damn, that IS a great idea!

And here I was going to suggest using an EZ Out to drill a counterclockwise hole in the screws to extract them.

[Dave W]

I've had good luck with screw extractors. Problem is, the screw shaft needs to be big enough to drill a pilot hole into the end. That' might be hard to do with your bridge screw.

Ready-made hole saws are meant to be used with an arbor and pilot bit, which won't work when you have a screw where the pilot hole needs to go! Plus, the smallest one I know of is 5/8" diameter. Too bad someone isn't making smaller diameter hole saws without pilot bits.

[Highlander]

You might be okay with a small ezyout in a brass screw but I never had much luck with the tiddlers... on Boeings, if we had to dig something out we'd just drill, retap, and fit a thing (iirc) called a helicoil-insert...

[Pilgrim]

It occurred to me that using the tubing trick, you's end up with a "post" of wood attached at the base when you back out the tubing/saw.  You'd have to wiggle the "post" back and forth to break it loose at its base.  Still seems possible to do with minimal cosmetic damage.

[Rob]

Here's a technique I've heard of on TB.

Get some brass tubing with interior diameter just larger than the remaining shaft of the screw.  You are going to make a hole saw with it, and remove a plug of wood with the screw shaft in it.

Cut about a 2" long piece of this brass tubing, then file V-shaped teeth into one end. This creates a very small diameter hole saw.

Chuck the tubing up in your drill, set the end of the tubing over the shaft of the screw, and start drilling slowly, my guess is that you'd want to do it in reverse.

You may grab the screw and back it out, but more likely you will drill out a plug of wood with the screw shaft in it.

You then can craft a plug to glue into the hole, then cut the plug off level with the surface of the body.  This will give you something to screw into.  It may require refinishing if the screw is not covered by some part of the instrument.

I have read multiple reports of success with this approach.  It's often used on bridge mounting screws or tuner screws. It does require plugging the hole, but that's MUCH cleaner and will impact less surface area than digging or chiseling out the screw shaft.

works well in fact Stew Mac has a steel version of it.  On Frets.com there is a better explanation and a picture .

Here's the expensive version but it will make sense.  http://www.stewmac.com/shop/Tools/Routing_bits/Guitar_Screw_Rescue_Kit.html?actn=100101&xst=3&xsr=3206

[Hörnisse]

Some great suggestions guys!  I really appreciate it. 

[Highlander]

Pricey but watch the video to be found on the link...

Al... if you got a piece of tube the right size it might "bite" and snap off by itself...

That SM kit has a slightly larger wall-thickness tube than the general brass tubing... it might be necessary to make a selection of "cutters" to cover all eventualities...

[Lightyear]

I think the tubing/StewMac idea is a cool idea.  But if it's just a flat plate bridge I still think the better part of valor is to drill right next/into the old screw and just run in a fresh screw.  Unless it's some kind of collectors piece or something. 

[Pilgrim]

Al... if you got a piece of tube the right size it might "bite" and snap off by itself...

That SM kit has a slightly larger wall-thickness tube than the general brass tubing... it might be necessary to make a selection of "cutters" to cover all eventualities...

A careful touch is definitely called for!