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1922 Gibson MB-3
Neck/Dowel Repair
© Frank Ford, 2007; Photos by FF
This old mandolin banjo has a familar problem.   The neck has pulled forward as a result of the high tension of eight strings tuned to pitch.  In fact, the neck has moved so far that the cantilevered fingerboard touches the head.
The neck attachment bolt has pulled loose and the heel cracked, possibly as a result of overtightening in an attempt to pull the neck back in to alignment.
Additionally, the dowel stick has warped considerably!
If you look closely,  you can see that the loose attachment bolt is pulling a section of the central black veneer along with it.
With the heel cap off, it's easy to see the problem and remove the bolt.
The bolt had a simple bend that would have held it agains the strain of tightening, except it appears that the black dye used in this veneer had caused it to deteriorate over time.
The dowel was completely loose, too, so it was easy to remove.  To compensate for the warp in the stick, I rotated it 180 degrees and reglued it in place with some nice fresh hide glue.
I replaced the loose section of dyed black wood with ebony.
In order to provide a solid mounting for my new bolt, I drilled out the heel using a 3/4" end mill to make a nice flat bottom hole.
A maple plug with the grain oriented at 90 degrees to the axis of the neck would resist splitting.
And, as another safety feature, I made up a new heel cap with a cross grain layer of maple underneath and an ebony layer for the outside.
Once I had the binding glued on, the heel cap looked as if it were solid ebony.
Here's the bolt I used to replace the L-shaped original.  It's a standard banjo neck attachment these days.
Set into the maple cross grain plug, the wood screws on this bolt will handle pretty much any amount of screw tightening.
Here's the assembly back together after a little finish touchup.
Now I can set this one up with a nice tall bridge and low action. . .

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