disaster struck, and I'm stuck ! all advice welcome.

[tonequester]

tonequester here.

Without going into the gory details, I have one half of a very small screw( the point and about 3 threads ) broken of in the back of my headstocwhich is very hard maple( un-finished ). It's a tuner mounting screw thats the culprit, and "no, I didn't over tighten it". It's "counter-sunk about
a1/16" deep. Since I'd obviously like to remove it without doing much damage that can't be hid by the Gotoh tuners that I'm installing, I'm looking for any advice/tips. The screw is much too tiny to drill out, and even I know how well trying to drill out a metal screw from any wood will turn out. The screw is also broken of quite jaggedly. I had the stupid thought of grinding of the point of a slightly larger bit than the size of the screw, and going down until I make contact.
Then use a Dremel and a fine guage cutting tip bit to remove enough around the screw so that a good, sharp pointed, pair of needle-nosed pliers might be able to extract the screw. If that worked, I'd attempt a good fill and patch job. However, I began to thing about that pointless drill drifting all over the place right from the
start. The screw fragment is NOT EVEN cinched down. I didn't want to strip the tiny Phillip's head. I even lubed the hole with a little beeswax before starting the screw. I"ve had a lot of experience at turning very little holes into very large holes, and I try not to go there anymore. However, it may well be my only option to
some degree. I thought that I'd give the forum a shot because in the month or so since I joined in, I have learned many things, and a few real jems. As I said,
any and all advice/suggestions/tips will be greatly appreciated. You can even call me a fool for getting in such a fix, I've been so named before. I will re-iterate
the fact that this was in no way my fault. It was in fact caused by a defective hex bushing which broke in half at less than one turn past finger tight. The resulting "rebound" of the tuning machine in the headstock caused the dinky mounting screw to pop as well. I inspected the threads of the hex bushing, and the part of the mounting screw that hit the floor. There wasn't the slightest trace of distorted threads. The bushings wall thickness in between threads is about a couple of thoudandths, and it's made of chrome plated "God only no's what", not steel. I hope to here anything from anybody on this one. At least Stew-Mac is
replacing both the bushing and the screw at no cost. Kudos to their customer service. That's the story. I know it ain't the end of the world, but at my at MY age,
time is almost as precious as peace of mind. Thanks to all who read, and a big thanks up front to anyone who takes a stab at this one. toneguester.

[J M Fahey]

Not a Luthier by any stretch of imagination, but *maybe* you can drill 1 mm holes around the broken screw, the idea is to remove wood around it so it grips on nothing and pull it like you would a tooth.
This will leave you with a jagged hole.
Drill it to turn it into a perfect cylinder and plug it with a tight fitting (and also glued) cylinder piece of matching wood, which you will later cut and sand smooth to the surface.
It should be an *almost* invisible job ... and as strong as the original wood.
Good luck.

[tonequester]

Luthier ? Perhaps not. Excellent idea ? Most assuredly !

Not a Luthier by any stretch of imagination, but *maybe* you can drill 1 mm holes around the broken screw, the idea is to remove wood around it so it grips on nothing and pull it like you would a tooth.
This will leave you with a jagged hole.
Drill it to turn it into a perfect cylinder and plug it with a tight fitting (and also glued) cylinder piece of matching wood, which you will later cut and sand smooth to the surface.
It should be an *almost* invisible job ... and as strong as the original wood.
Good luck.

tonequester here.

JM, you are right on track with your advice. I had checked earlier and hadn't recieved a reply yet. If you are like me things like my broken screw
in the headstock are hard to get off your mind. It's not so much that I worry, it's more like I don't the fact that a job that was going great, got the best of me on
literally the last turn of the wrench. I had the time, so I decided to play it by ear. I looked at the slightly counter-sunk screw and had a sudden, very similar idea
to your idea. I didn't have a 1mm bit(I'll be for getting one now), but I took a finish nail and ground the pointed end almost needle sharp, for about 1/4" from
the point. Then I went all around the screw tapping it in about a mm at a time, each hole as close to the last as I could. After each circle I picked out what wood
remained. About 5 circles and 10 minutes later, I noticed the remains of the screw moving. I sharpened the tip of a small pair of needlenose pliers, and plucked
the damned thing out on the first try. Tomorrow I'm going to plug and finish the hole just as you suggested. I've already found a small piece of maple that is a
great match. If I would have had the 1mm bit it would have been even easier. I meant it about picking one up for just such an ocassion. That small of a bit allows
you to get the job done without enlarging the hole much at all. As a matter of fact, in my case, the new tuner will hide about half of the patch.
Thanks so much for the reply as I had looked at the piece of maple that I found and then had the thought "too much work". I had talked myself into just using wood filler. Your idea will look better, and I bet that it will hold the new mounting screw better as well. The screw extraction went so well in such a short time that their is not a good excuse to rush to a cheap patch job, when I can do it right the way you suggested.

Thanks again for the reply, and reminding me about QUALITY ! tonequester.

[52 Bill]

If you do a little research Dan Erlwine has a method to remove those broken screws. He takes a short length of brass tubing that is sized just big enough to fit around the broken screw. He then files saw shaped "teeth" into the end of the tubing. Then he uses this hollow drill to cut around the screw until it can be removed.

Obviously, don't cut any deeper than necessary and then plug the hole with a dowel made from matching wood.

I don't know if this is one of the tips available at the Stewmac site or not. I think that it was published in the Guitar Player repair book.

[Bruce Johnson]

I repair broken off screws like that quite often in my restoration work. Tuner screws, pickguard screws, strap button screws, and pickup mounting screws.

The method is what 52 Bill is referring to, using a special core drill. A core drill is a hollow tube with teeth on the end. The ID is sized for a slip fit over the screw, and the OD is sized for a common size of wood dowel. They are real easy to make up in any size you need if you have a metal lathe. I have an assortment of them that I've made up in standard screw sizes. I typically make them up from O-1 tool steel (drill rod), hand file the teeth in the end, and then harden them with a propane torch and an oil dunk.

You can make a one-shot core drill from brass tubing, but brass is kind of soft. Some small steel tubing would be better, any kind of steel.

Do you know any local hobby machinists? It's a simple job. If you can't find anyone, contact me and I'll make one for you.

[tedmich]

use EDM to burn it out?

kidding

McMaster Carr has 6mm hole saws
4093A31 $7.34
Heavy Duty HSS Hole Saw 1/4" Diameter
arbor
4093A71 $15.67

(you have to work around any requirement for pilot holes or center drills, and I haven't tried modding this arbor, caveat emptor)

1/4" dowels are available in many woods and even different grain orientation but you can cut your own cheaply too
2806A11 $10.73
Wood-Plug Cutter 1/4" Plug Dia, 3/8" Max Plug Length, 1/2" OD

an alternative tact is just using a small diameter center cutting carbide end mill and carefully cutting out the metal, and then plugging the resultant hole. Slow even feeds are required and difficult to do with a drill press, and if you break the carbide you are (more) screwed...

OR using micro end mill or stub drill and putting the hole in the broken screw and then backing it out with an extractor, this drill extractor combo works on screws as small as 3mm
53405A41 $9.80


(learn to use paraffin wax on screws )

[Bruce Johnson]

By the way, I never use those screws that come with the tuners. They are horrible, made from some metal that has the structural properties of cheeze. They either snap off at anything over 3 in-oz of torque, or the heads strip out. They automatically go in the trash.

I buy small sheet metal thread-forming screws, usually #2-32 x 5/16" pan head phillips. Sheet metal screws are made from hardened steel, and it's pretty difficult to snap one or strip the head. The "thread forming" style have a blunt nose and a coarse thread. The specific ones I usually use are from McMasters, number 90056A078. No need to plate them. They come through in a semi-bright zinc plating. I hold them in a pin vise and hold the head against a buffing wheel, and they look almost like chrome.

[Chuck H]

I typically make them up from O-1 tool steel (drill rod),

Where do you get, or how do you make hollow O-1 drill rod?

[Bruce Johnson]

Tool Steel rod stock, commonly known as Drill Rod, is available from any metal supplier. I usually buy mine from McMasters.

Here's their page about tool steel, which has some good general info: McMaster-Carr

Here's the page of O-1 grade tool steel rod stock: McMaster-Carr

O-1 is a general purpose tool steel, and you can see it's available in hundreds of diameters. It's precision ground to accurate size. It is supplied in annealed (soft) condition, so it can be machined with normal tools. You can saw it with a hacksaw, file it to shape, and drill it with normal HSS drill bits. When you have shaped it into whatever you want, you heat it up with a propane torch to a dull red hot and dunk it in some oil. This hardens the steel to the point that it can be used as a tool bit to cut other metals. That's why it's called Tool Steel. It's the metal that you use to make cutting tools.

To make a core drill for removing broken screws, pick a diameter of rod based on what size dowel or plug you want to use to fill the hole in the wood. An easy choice for small screws is 1/4", because 1/4" dowel stock is commonly available in birch and other woods. If you are making your own dowel plugs, then you can choose any OD that you like. Saw off a short length of the rod, maybe 2", with a hacksaw. Put it in the chuck of a metal lathe and face off the ends. Drill a hole in one end, of a size just slightly larger than the OD of the threads of the broken screw. Then clamp it in a vise and file the shape of the teeth using a small triangular file. On a little one, you can make it with 1 to 4 teeth. When the shape is right, heat it with a torch and quench it in oil to harden it. If needed, touch up the cutting edges of the teeth with a small sharpening stone.

Attached is a quick picture of a core drill I made specifically for removing broken pickguard screws. It's 1/4" OD with two teeth. You can see how the teeth are shaped, just a hook and a ramp. On this one, I've "relieved" the OD also. That is, I've turned down a section of the OD a little bit behind the cutting end. This isn't absolutely necessary, but it keeps the bit from squealing in the wood as it goes in deep.

As long as you have access to a metal lathe, even one of the little benchtop ones, a custom bit like this is easy to make. One of these takes me maybe 20 minutes to make up.

[tonequester]

somebody up there likes me afterall !

I repair broken off screws like that quite often in my restoration work. Tuner screws, pickguard screws, strap button screws, and pickup mounting screws.

The method is what 52 Bill is referring to, using a special core drill. A core drill is a hollow tube with teeth on the end. The ID is sized for a slip fit over the screw, and the OD is sized for a common size of wood dowel. They are real easy to make up in any size you need if you have a metal lathe. I have an assortment of them that I've made up in standard screw sizes. I typically make them up from O-1 tool steel (drill rod), hand file the teeth in the end, and then harden them with a propane torch and an oil dunk.

You can make a one-shot core drill from brass tubing, but brass is kind of soft. Some small steel tubing would be better, any kind of steel.

Do you know any local hobby machinists? It's a simple job. If you can't find anyone, contact me and I'll make one for you.

tonequester here.

I too wish to thank Bruce Johnson for the excellent tip. I did not know "such an animal existed". Using a sharpened nail. I carefully enlarged the hole until i noticed the screw remnant moving. A sharp pair of needle-nosed pliers plucked it out. I did a pretty good fill job on the hole which was completely covered by the tuning machine. I drilled a pilot hole for the new screw and carefully snugged everything down. I was darned lucky. Thanks for the offer of making me a tool. This forum seems to have an abundance of good hearted people, who in addition have good heads on their shoulders !

If being the least among many, I can ever be of service to any of you folks, just give a "hollar". tonequester.