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A good test of nerves. . .
Concealed Dowel
© Frank Ford, 8/18/02; Photos by FF
Up until the early 'teens, Gibson mandolin necks were laminated with a center strip of 1/8" thick dyed wood. Unfortunately, the dyeing process quickly resulted in a serious degradation of the structure of that lamination. With time, the black lamination achieves the structural integrity of a charcoal briquette. What looks like a simple regluing turns out to be a bit more nasty, as the black layer continues to crumble.The fingerboard and dovetail joint tend to keep the neck together, but the peghead is vulnerable to breaking open.
Later, Gibson switched to using a solid piece for the peghead, and running the black line as a shallow decorative inlay so this damage would not occur. So, we're left with a population of thousands of instruments, mostly mandolins, with a potential problem. If we simply reglue the lamination, chances are it will break free and surprise us later on. I think it's a good idea to add some rigid stiffening reinforcement so the peghead can't flex.
First, a bit of new glue to hold things together.
I clamped the peghead against a flat plate in the front to align the halves, and from the sides to close the joint.
First checking the grain direction so as not to make a big mess of things, I positioned the peghead over a hole in my bench, and drove a tapered violin peg into the hole, neatly splitting a nice section off the side.
Over at the drill press, I drilled a 1/4" hole right through the entire peghead, starting in one tuner hole and punching right through to the tuner hole on the opposite side.
I sanded a 1/4" dowel just a bit to make it fit the hole neatly, and tapped it all the way in with a load of Titebond glue.
After I trimmed the end of the dowel where it entered the hole, I was ready to reglue the piece I had broken from the peghead.
Here again, I used flat plates on the front and back sides, along with the edge, so the broken piece would be realigned perfectly.
This instrument's finish was a bit rough overall, so I decided not to do too much touchup on the peghead, for fear of making it look out of place. Instead, I added just enough shellac by French polishing to fill the hairline crack left when I reglued my broken side piece.
Even if you zoom in for a really close inspection, you can hardly see my intentional crack after a few swipes with the French polishing pad.
And, now that the job is done, there's still a bit of evidence of the original crack, and most of the original scars and dings are show on the surface of the peghead. That 1/4" dowel adds a lot of strength to the peghead, so there's no chance of it coming apart again. Another perfectly good reinforcement would be to use a wide spline at the end of the peghead, but it would be a more visible repair. As with so many other repair options, it's a judgment call.

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