|Building my 2nd
Acoustic Guitar - Page 6
July 19, 2008
After the headstock debacle, I reviewed my options. There were only three, really: Keep the thing and make
the best of it (no), try to repair the neck (and save the work on the tenon) by maybe cutting off the headstock
at the scarf joint and putting a new one on (no!), or just bite the bullet and make a new neck. So I ordered a
new headplate and got to work on the second of two neck blanks Paul Lloret generously gave me. This blank
was just scarf-jointed, so I put on a laminated heel. I rough-cut the back curve of the heel on the bandsaw
and then took some waste of the sides of the heel as before to reduce the shoulder area I'd have to deal with
when I went to fit the tenon:
Then I went to trim the sides of the headplate flush with the 'ears'. I did this on the tablesaw,
cutting the first side nicely flush, just like I wanted. I trimmed that (left) side with the neck
pointing back at me since the fence was to the right of the blade. To do the other side, I simply
turned the neck around and reset the cut width. But in another moment of LOB (lack of brain) I
aligned the saw with the side of the neck, not the previously-trimmed ear. I realized my error, it
turns out, just in the absolute nick of time and stopped the cut with room still remaining for the
profile. Only a very small bit of the 'ears' will end up being used. This is how it looked after I
cursed myself and trimmed it properly.
After that operation, the neck looked like this:
Then I glued on the 'wings' that fill out the headstock width. I tried very hard to make them the same
width and aligned properly... the random-sized ones I used before caused me lots of headaches in the
layout process. Then, while everything was still square, I drew a series of index lines across the back.
These will help me keep everything aligned after I profile the sides, otherwise because of the taper (and
eventually the curved top) it is very tough to figure out what 'straight' is.
Then I measured the 'break angle' between the neck and headstock (15 degrees on this guitar... some
builders like a sharper angle, such as 17 degrees). I set my tablesaw blade for that angle and mitered the
end of my new headplate so that it will be 90 degrees to the neck when glued on. This gives a good
bearing surface for the nut. Note: As I metioned before, The design for this guitar (and Martin's standard,
apparently) had the nut (the string side) directly on the 'break', meaning the nut itself is on the slope and
thus is not square -- the top drawing below. I decided to move things around a bit and put the nut on the
flat part of the neck so that it will be easier to fit (bottom drawing), essentially lengthening the neck
(though not the scale) by the width of the nut.
The headplate miter is the same either way, but the location shifts. In any
case, here is the neck with the headplate glued in place.
The reason I wanted to trim flush to the outside edge of the ears was to make it easier to extend the index
lines from the back to the front of the headstock. Again, to ease the layout. And it's remarkable how
useful that is, because all the laying out of the profile and positioning of the template is done on the front
side because the back is not as long -- the neck extends farther on the back of the headstock because of
the angle. But you have to cut the profile with the headstock facing down so it will lie flat. Therefore, all
the laying-out that you do on the front has to be transferred for the back for cutting, and the index lines
make it much easier.
So I laid out the sides of the headstock and cut them out on the bandsaw, following with files
and sandpaper to smooth.
Once that was done I laid out the slots. First I located the center of the arcs at each end of
each slot, transferred them to the back, marked the position with a small awl hole, then scribed
a line between each slot's centers. I drilled 1/2 inch holes at each center. Then I used a 3/8
inch bit to waste out the bulk of each slot, carefully centering each hole on the scribed line. By
the way, brad-pointed drill bits are absolutely necessary for this kind of work.
This is exactly where I started screwing up the other neck, but I was more careful. I used a
thick board with a true 90 degree side. I scribed the edge of the slots -- edge of end hole to
edge of end hole -- and clamped the thick board right on that scribe line. Then I carefully
used a very sharp 1-inch chisel held tight against the thick board to true the edges of the slots.
I had finished the outer side of one slot when I realized I had forgotten to drill the tuner holes.
That needs to be done before cutting the slots so the wood supports the entire depth of the
hole. If you wait until the slots are cut you risk chipping out chunks when you come out of
the side and into the slot. Fortunately, I had only smoothed one side of one slot, and the other
three roughed-out slot sides could absorb a little blowout with no problem. So I carefully laid
out and even more carefully drilled the tuner holes On the smooth slot side I stopped when
the bit was poking only partially out, and carefully chiseled and sanded the 'exit wound' clear.
Then I continued and drilled the rest of the hole in the center of the headstock. Still suffered
some blowout, despite my precautions. Lesson: Drill the holes before the slots!
I finished smoothing the first slot and began on the other. Then I blew out a bit of the
headplate. Remember I'm working from the back. That's where I am as of this photo...
repairing the cracks in the rosewood headplate. I'll probably trim away most of what I'm
repairing here as I finish the slot, but hey.
By the way, I'm only showing all these screwups because they're educational!
July 21, 2008
I completed the slots in the new neck's headstock. Careful trimming and sanding (much more
careful than last time!) did the trick. Still not perfect but definitely acceptable. I'm going to
wait until later to cut and inlay the 'key' at the tip.
It had been my plan at this point to proceed using a router and a template rather than risk the
kind of tearout/sanding problems that ruined the previous slots. I made a template of 1/4 inch
mahogany that, lined up with one side of the headstock, would have done the job nicely. I was
going to use an end-bearing flush trim bit with the template on the bottom. I would drill the
end holes and rough out the center waste, then place the headstock on the pattern, lower the bit
so that the bearing was inside the pattern's slot, then bob's your uncle. However, my smallest
flush-trim end-bearing bit was a half-inch diameter, which is the width of the slots. So I
punted on that idea and resolved to do it with chisel and sandpaper again, but do it right.
Then I turned again to the heel. When I was cutting the curve of the heel I (of course) cut a bit
inside my intended line, leaving only a little wood for the final heel. That won't be a big problem
-- I'll just have to alter my intended profile, but I am a bit concerned about the strength of the
heel with the reduced amount of wood. So I drilled a hole most of the way through the heel and
glued in a pencil to reinforce the short grain. I didn't have any appropriate sized dowels, and a
round pencil is, I hope, strong enough for this purpose.
And so the guitar begins to take shape! The fretboard is Madagascar Rosewood; the tuners are Gotohs. I am going
to put a binding on the fretboard but the binding is backordered so I have come to a standstill.. When I have done
the fretboard binding I will profile the neck and do the preliminary neck shaping. Final neck shaping will wait until
the neck is joined to the body and the fretboard glued on.
Along the way of course I also cut the truss rod slot and fit the dovetail tenon to the body mortise (not
photograped because they're just like the first go-round). I did a somewhat better job fitting the tenon this time,
too. Once more through the endless chiseling, filing, sanding, testing fit, repeat. The dovetail is really a pain in
the butt compared to a straight tenon. As I have found out (twice now!), there are the same number of
surfaces, but the dovetail is exponentially more difficult to fit, because it's much harder to figure out the cause
of any misalignment or misfit. No magic, just go slow and be patient. I found a feeler gauge to be helpful...
The reason for being so fussy is that you're trying to get all these things right at once: a) the neck angle, which
depends on the angle of the shoulders and the end of the tenon; b) The top of the neck has to be completely coplanar
with the top of the upper bout and not tilt right or left; c) the mortise and tenon need to be a tight fit, with as much
contact as possible; and d) the intersection between the shoulder and body should be as tidy as possible. In fact, I
fiddled with it for so long that the shoulders retreated a milllimeter or two and now the 12th fret falls just inside the
body join rather than right on it. But I'll trade a couple of millimeters for shoulders like this: