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. . .