Update: this thing fell apart rather quickly. If you decide to try this, either use something stronger than epoxy putty to hold the "threaded screws" (I still haven't found out the proper English term) together or find another way basing on the same general principle. I might write another instructable on the subject matter some time.
In this Instructable I will show you one way to build a simple tool that will help you to install, remove or re-install bridge mounting posts for Tune-O-Matic style bridges that go directly into the top wood of an electric guitar.
This particular tool is inspired by the Tune-O-MedicPost Tool that is available for purchase at Stewart-MacDonald for $22.95. However, I'm cheap, have no credit card and live in Germany, so apart from not being able to buy/mail-order it in the first place, shipping and taxes would greatly increase the price I'd have to pay for this simple tool.
I'm slowly building up a collection of specialised tools, home-made ones as well as actual professional tools and I figured it wouldn't hurt sharing some information and experience along the way.
There are, of course, much more simple and most likely cheaper ways of achieving this using the same principle as this tool. I'm going to give you alternative ways of building such a tool at the end of this instructable.
A little bit of background:
On some older electric guitars (as well as some replicas, reissues, copies/knock-offs), the bridge is connected to the body via two threaded posts that are screwed directly into the top of the guitar. The bridge itself rests on two knurled nuts that allow for the height of the bridge to be adjusted. (See first picture) Modern bridge designs, as well as 'stop' tail-pieces, use bushings that are installed in the top of the guitar. These are knurled on the outside and threaded on the inside to accept the post. (See second picture)
If you want to refinish your instrument or install a newer bridge that has poles that require threaded bushings, you will obviously want to remove these posts.
To my knowledge, this type of bridge, the so-called Tune-O-Matic bridge, was introduced by Gibson with their Les Paul model solid body electric guitar in the mid 1950s.
Also, other stringed instruments with arched tops such as mandolins, bouzoukis and hollow-body electric/acoustic guitars with arched tops and backs (aka jazz guitars) use a similar way of installing the bridge. With these, the bridge (often a adjustable Tune-O-Matic style bridge or a compensated wooden bridge) rests upon a wooden base that is scalloped on the underside to fit the arched top.
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Step 1: Gathering Tools and Materials
A) Raw material:
- A cheap screw-driver for slotted head: This will be the "handle" of your new tool. I chose a driver for use with carburettors (at least that's what the sign on the shelf at the hardware store said) that has a short tip and handle. About €3
- Three M4 (metric) or 6-32 thread (imperial) thread-screws (at least that's the literal translation of what they are called in Germany): These are basically hollow screws that have a thread on the outside to be screwed into wood and a thread on the inside to accept screws themselves (See image/sketch). About €.25 each.
- Metal or plastic pipe. The inner diameter has to be just as large or larger than the outer diameter of the thread-screws.
- File and sandpaper
- Saw. If you're using a metal tube the blade should be suitable for sawing metal, if you're using a plastic tube, you can use a wood saw. The blade shouldn't be too coarse, though, or else you will end up with a rough edge.
- Screw driver for slotted heads (optional)
- Epoxy putty
- Epoxy resin
- M4 or 6-32 threaded screw, just long enough so that you can fit your three thread-screws onto it.
- Washer that fits the screw
Step 2: Assembling the Threaded Cylinder
The first actual step in building the tool is to assemble the "threaded cylinder":
Put the washer on the screw and then screw the thread-screws on the screw, the "prettiest" side (i.e. one that isn't slotted) facing the head of the screw as it will be visible when the tool is finished. Make sure that the slot that is usually there to screw the threaded screw into wood on the last screw is facing the end of the contraption. (First schematic)
When everything sits tightly, take a bit epoxy putty and apply it uniformly on the outer thread.
If the washer has the same outer diameter as the pipe you are using, you can apply the putty all the way along the thread. If it does not, leave a bit of space between the putty and the washer (See second schematic and photograph).
Now take your cheap screwdriver and insert it into the slot. Put some putty onto both sides of the tip to form a tight plug that safely shuts the inner thread. Leave the putty on the screwdriver and put it aside, this plug will be essentially later. (See 4th schematic)
Leave it to harden following the instructions given with the putty.
Now that the putty is hardened, you will want to file/sand off any excess material. File/sand off just enough so that the outer thread is filled and you have an even cylinder. (Third schematic)
Insert that threaded cylinder in the pipe to see if it fits. If it's too narrow, no problem, just add more putty and file/sand down the excess until it fits (Note: all schematics are drawn with the pipe and the threaded cylinder fitting). If it is too wide, same MO: file/sand away the excess material until if fits.
Step 3: Prepare the Pipe
Connect the threaded cylinder and the screw driver. If you have done it right, the extra putty on the tip of the screw driver should seal the inner thread perfectly. now measure the length of the part of your tool that will be inserted into the pipe and cut a piece of pipe of the exact same length. If you have chosen a screw driver with a rather long neck, you can also take a shorter piece of pipe.
Having cut the pipe, file/sand the edges until they're smooth and even.
Quickly assemble the whole thing to see if everything fits:
Insert the threaded cylinder from one end and the screw driver from the other. Ideally, the tip of the screw driver now fits into the slot at the end of the threaded barrel and the washer is levelled with the outside of the pipe.
I don't think these steps require detailed pictures, they're pretty self-explanatory.
Step 4: Final Assembly
Remove the screwdriver and the cylinder from the pipe.
Prepare some epoxy resin following the instructions given on the package.
Pour some on the inside of the pipe. Be careful, though, you want the resin to rest on the walls of the pipe. Now insert the screwdriver again and make sure the end of the handle and the end of the pipe close tightly. Then add some more resin from the open topfoot note, uniformly distributing it along the inside of the pipe. Then slide in the threaded cylinder and turn it until it's slot latches onto the tip of the screw driver.
The resin should now flow down the inner wall of the pipe and connect the threaded putty cylinder and the screwdriver tip with the pipe.
Alternatively, if you have cut a shorter piece of pipe you can just continue where you left after step 3 and pour some of the resin into the back of the pipe until it levels with the edge of the pipe.
After allowing the resin to harden (again, following the instructions given on the package), you can now unscrew the screw that's still in the threaded cylinder (I forgot to draw it in the schematic, though).
If the washer should fall off, that's not a problem. As long as the surface is even, you will be fine. If it isn't, simply fill any cavities with putty and sand/file it flat if necessary.
I chose not to fill up the gap around between the outer pipe and the inner cylinder because it's a) all shiny metal and b) the gap is just at the tip, after the first turn of the thread it looks just like I have drawn it in the schematic.
Congratulations, you have now completed your very own brige post removal/installation tool.
Foot note: Actually, using this method, it's not necessary that the tip of the driver and the slot at the cylinder seal the cylinder, but I changed my approach in the process of making the tool. Originally, the plan was to leave the cylinder in the pipe and add the resin from the back end and having it cover the inside walls of the cylinder. Then I was to insert the driver and turn the contraption around with the 'business end' facing the ground. The resin would then slowly flow down the pipe and cover the connectin between the driver tip and the cylinder just like pictured in the schematic. Changing my plan allowed for two separate applications of resin so that both the end of the pipe is connected to the handle of the driver and enough resin is still at the region where tip and slot join.
Step 5: How to Use It
Here's how to use your new tool:
(I'm not going into great detail about how you should handle your guitar while performing maintenance work on it, I'm rather sure you have your own ways of preventing accidental damage)
Un-string your instrument and take off the brigde. Screw the tool onto the bridge post until it reaches the knurled nut. Now screw the nut against the tool and hold them both together tightly. You should now be able to remove (or install if respectively) it by turning the whole contraption like a regular screwdriver! That means turn clockwise to install, counterclockwise to remove.
Step 6: Afterthoughts & Alternative Ways of Constructing the Tool
If you don't happen to have the required material(s) lying around in your shop, you'll probably invest a little less than the tool that StewMac offer would cost you. I had some epoxy putty left over and a found metal pipe in my shop that was just perfect so I ended up spending only about �4.75 on the parts for this tool and about �7 on the epoxy resin.
Also, I have realised with the benefit of hindsight, that this is a rather work-intensive and time consuming way to realise this simple tool, although the result is rather professionally looking.
Even though I'm probably not going to order anything from StewMac any time soon, I ordered their free catalogue which they even ship overseas without charge. There's a lot of information and inspiration to be taken from the catalog so I suggest you do the same.
StewMac is also offering a free weekly Email newsletter called Trade Secrets in which luthier Dan Erlewine is offering useful tips, how-to articles and the likes, often with the help of guest editors. (at least that's what it says on their website, I've only recently learned of this newsletter.) Of course, he's using StewMac products while demonstrating those.
Comments, tips/hints/advice and (constructive) criticism are always welcome!
And now: Alternative ways to create the same tool
1) If you happen to have thread-cutting die that will cut the desired thread (M4 or 6-32 thread respectively), you can go and buy a simple extension nut (that's a long nut with a hex shaped outside) and a cheap screw driver that should have a neck about 4mm or 6/32" in diameter. Cut off the tip with a metal saw, use the die to cut a thread on the tip and screw the extension nut into place. Fix the nut with epoxy, or drill a hole through the nut and the tip and connect them with another bolt. Unless you have to buy the necessary tools, you'll end up spending a lot less than you would following my instructions and you'd still end upt with a good looking tool.
2) You could also skip the pretty parts and just connect the thread and the screw driver by applying a large blob of epoxy putty, rendering steps 3 and 4 unnecessary. Not very professional looking but it will do the trick.
3) Just take a nut with the appropriate thread and a clamp and apply it the same way as depicted in step 5. That would probably be the cheapest but also the least professionally looking way to do the trick.