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Back to the Future*
"Downsizing" Tuners
© Frank Ford 2003; Photos by FF

The guitar in question is a 1940 D-18 that originally had Kluson open back tuners which had been replaced by a different set of open back Klusons, which in turn had been replace by Grover Rotomatics.
For some reason, I don't have a good "before" picture for this article, so I'll use this one. The tuner hole on the left is the typical 3/8" hole needed to mount the Grover Rotomatic tuners. It's way too big to remount the original tuner and bushing.
Here's another guitar, showing the outline of the original Kluson open back, peeking out from behind a Waverly reproduction Grover G-98. The 1940 D-18 in question had both this scar and the big hole illustrated above.
At least it wasn't messed up like this one, with its extra off center screw holes.
I decided my first job was to fill the holes so I could redrill them properly for the smaller shafts and bushings of the old gears I would be mounting. In fact, the current owner of this guitar took off the second set of vintage open back tuners that had been mounted on the guitar when he bought it 25years ago. He kept them, but drilled out the peghead and installed the Grover Rotomatics, which were mightily popular in those days. Now, don't chide him. It was definitely the thing to do at the time.When he wanted to go "back to the future" (that is the second set of gears) he had them handy.
I used this machinist's taper pin reamer from the back side (see above photo, too) to make the holes uniform and round without enlarging them at the surface of the peghead. The holes had not been so neatly drilled, and they appeared to be slightly different diameters, too.
I have a matching plug cutter I made with the same taper as the reamer, and I used it to plunge into some thick mahogany and turn out some pins to fit the holes I'd reamed.
The plug has the same grain orientation as the peghead. I didn't think a straight dowel would hold the bushing as well as the end grain exposed on this kind of plug once I drilled it to fit.
Sticking the plugs in the holes, I could see that they fit at different heights, reflecting the different diameters of the redrilled holes.
I marked the lengths and cut them fairly close so I wouldn't have too much to trim off later.
A quick pencil line gave me a reminder of grain orientation.
Because these holes AND the plugs presented a substantial amount of end grain, I chose to use epoxy, which holds very well in that application. It forms a matrix in the pores of the wood and has terrific cohesive strength.
The plugs tapped neatly and tightly in place, lubricated by the epoxy.
After trimming with a chisel, I drilled the holes, and gave the top edge the slightest little bevel to avoid chipping when the bushings went in.
Here's a closeup of the result.
And, here's a shot of the back surface, showing the scars from all three sets of tuners. The pointy scar is from the original, the big circular one is from the Rotomatics, and, if you look really closely, you can see the little rounded tab scar at the top center, made by the second set of tuners.
The original finish was in good shape everywhere, so I chose to add just a tiny bit of stain to the margin of the new wood that showed at the top. I didn't want it to shine through at the edges of the original bushings.
The result was quite nice.
From the back side, the second set of tuners pretty much covers the scars underneath.
The second set of tuners looks good, and even though the bushings are quite small, you don't notice any modification of the peghead veneer. Fortunately, even the Rotomatic washers made very little impression in the surface.

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*Since I was reinstalling the second set of tuners which were an "upgrade" at the time they were first used, I figured I could get away with the "back to the future" thing. . .