Tacoma Thunderchief Headstock Repair

November 29, 2017

This Tacoma bass was in the shop recently for a broken headstock repair. Someone already attempted a repair, but the glue up failed. This makes fixing it properly a bit more difficult the second time around, as the glue residue left over from the previous attempt can weaken subsequent glue ups..

Whoever attempted to fix this bass the first time around sanded most of the finish off of the back of the neck.

They also didn’t do a very good job of getting all of the gluing surfaces to fit tightly together. Pieces of the peghead overlay were sticking up, rather than having been glued back in place. As I was handling this instrument,  a few of these pieces actually fell off in my hands. The overlay was completely shattered.

I suspect that the first repair failed because of a poor fit. Ailphatic and PVA wood glues aren’t great gap fillers; they can provide you with a very strong glue joint if the two mating surfaces fit tight and cleanly, but if the two pieces of the headstock were not joined back together properly, the joint will be severely weakened.

After removing the tuners, I started by removing as much of the old glue residue as possible with vinegar, which dissolves most wood glues. I then glued the headstock back in place with West Systems G Flex epoxy.  The above photo shows what I’m left with, and it’s not too pretty. Sometimes, a damaged peghead overlay can be salvaged, or patched up somewhat, but this one was trashed. I decided in this case to replace the overlay entirely. So I took to Google images, in search of a jpeg of the Tacoma logo. Once I found this, I vectorized it in Inkscape, and emailed it off to a friend of mine who owns a laser cutter.

Here’s what he came back with. The original headstock veneer was laser cut in the same manner, so the logo is an exact match. The mahogany that I provided for the overlays, however, was quite a bit lighter, so it’ll need to be stained after installation.

First, I hogged off most of the old peghead veneer on my belt sander.

I can’t sand off the entire veneer on the belt sander without damaging the fingerboard, so I carefully chiseled the last bits of it away, and cleaned everything up with a block plane. Then, I checked the freshly exposed surface of the headstock with a large machinists square, to make sure it was flat in all directions.

I decided to reinforce the headstock reglue with splines as well. Normally, the splines are routed and installed through the back of the neck, spanning the crack, which would strengthen the glue joint, but be very noticable and unsightly. Since I’m replacing the peghead overlay, I decided to spline from the front instead. Here, I’m tracing out in pencil where I want the splines to be located. I scribe the lines with a razor, route out the majority of the channels with my dremel, and then square off the corners with a chisel.

I then install the splines with epoxy. These splines run deep through the headstock, and fit very tightly. After this photo was taken, the splines were clamped down into their channels, and then the epoxy was given 24 hours to cure.

After the epoxy is set, the splines are trimmed down with a chisel. I’ll again check the face of the headstock with a straight edge to ensure that it is flat and level. Finally, I’ll remove the truss rod nut, and then mask off the truss rod access channel with tape, to prevent it from being filled in with glue when the peghead veneer is glued in place.

The laser cut veneer is glued in place using West Systems epoxy, and a flat clamping caul.

After the epoxy has cured for 24 hours, the excess is trimmed neatly to match the headstock profile. I then drill the tuner holes through the new veneer. After all that is done, the new headstock veneer is stained to match the surrounding finish.

I apply a water based stain, and then spray on a product from Mohawk called Wax Wash, which I use to preview how much darker the stain will look after I’ve applied a finish. Since the stain I’m using is water based, I can blot out excess stain with a wet rag if I need to lighten it up a bit. It takes a couple of attempts to get the color match spot on.

Next, the headstock veneer, along with the back of the neck, where the finish had been removed by the previous repair attempt, is oversprayed with Mohawk Perfect Blend semi gloss lacquer. The original finish is open grain, so I do not need to use a grain filler before spraying.

Then, I cut a slot for the nut…

...and open up the truss rod access channel, by first drilling through the peghead veneer, and then cutting the channel to shape with a knife, before cleaning it up with sandpaper.

There’s one last step before this job is done. The original truss rod cover was broken when the headstock came off. It was also caked with wood glue, as the original repair person neglected to remove it before gluing. The original truss rod cover was made out of a sheet of black fiber veneer, and I happen to have a large sheet of this stuff that I use for a variety of purposes, so I decided to go the extra mile and replace the truss rod cover for no additional cost. This fiber veneer is thin enough that you can cut it with scissors, it took less than five minutes to make a replacement cover.

Here’s the finished product.

The backside of the neck isn’t beautiful; the glue joint was fouled up enough by the previous repair attempt that it was impossible to make the seam disappear.

But looking at it head on, you really can’t tell that it ever broke.

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