Cover
Contents
Preface
Terms
Design.
Materials.
Construction.
The Neck.
Appendex.
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Select this piece with care, it is the heart of this instrument.
Choose wood that has had time to dry and reach an equilibrium
with your local humidity. Freshly cut wood may tend to warp as it
dries and this would be disastrous if it warps after being made
into a neck. The wood I selected had been drying for several years
thus, any warping (which is the strain caused by the stress
created from an uneven drying), has already taken place before I
begin squareing the stock.
This same piece will also become your headstock and
fingerboard.
 Grain should run
the length of the board and the individual layers of wood should
also run from front to back of the neck.
This will result in
your neck having the greatest strength possible in support of the
strings, and the least bending of the neck. (This is opposite of
the desired effect of an archers bow from which stringed instruments
originated and where flex is desireable.)
Here is a cross
section of how this piece may have been cut from the log, and how
four pieces may be cut from a single log.
Square the board true by machining all four sides and both ends.
One face of this board will be the face of the fingerboard
portion of the neck and should be treated respectfully so as to
avoid scaring it through the processes. If a laminated headstock
is desired or required (due to the available lumber sizes,) Then
machine the surfaces to be joined, glue them, and then machine
the stock back to square. For Cocabolo wood I use acetone to help
clean the wood before joining with (ethyl) cyanoacrylic glue and
waiting several days before unclamping.
Machining the neck.
- Layout your cuts by marking (lightly drag) with a white, very sharp
(sharp in the sense of creating lines a hundreth of an inch wide,
and not in the sense of digging into the wood) pencil (I prefer
Berol Prismacolor pencils.)
directly on the stock. You will need to maintain reference
points, edges, and surfaces to measure from so try to make all
your measurements from the same starting point. As your stock should
be square and accurately machined to the initial dimensions, you
may select the face of the fingerboard as a plane to measure
from. The sides of the stock should also be accurate and may also
be used to measure from. Marking your cuts will keep you from
making a gross error, but you should rely upon measurements for
setting up the actual cut and use the marks as a visual
confirmation the the cut is about to be made in the correct
place.
- Remove the material from the front of the tang leaving a
shelf (from which you may measure toward the headstock.) Draw a
line where the nut meets the fingerboard across the fingerboard
indicating where the taper of the headstock will begin. Machine
the groove for the nut, after measureing from the tang as you
would normally do when machining and using the line you marked
as a visual double check. (Place a precision piece of
metal rod stock in the mill and using a piece of cellophane
or a cigarette paper as a feeler gauge, bring the rod into contact
with the edge of the stock so that it is just the thickness of
the gauge away. Raise the bit and change it to the bit to be used
for the nut groove. Move the milling machine table so that the bit
will be ready to begin cutting by moving the thickness of the paper
gauge (typically 0.001 in.), and the radius of your rod, and the
distance to the nut groove, and half the distance of your bit, plus
a smidgen more to place the bit near the center of the cut.
You should be able to know exactly where the bit is at all times
so that as you machine your groove you will be able move the table
of the milling machine to work your way out from the center of a cut
to the edges. The backlash of some machines will require you to
periodically measure the width and depth as you are cutting
to be precise. Your final passes should be removing 0.001 in.
at a time to give best results, and you may notice that it may
take several (spring) passes (without moving) before the bit stops
cutting due to stresses in the bit amd machine.)
- Machine the face of the headstock, then turn the piece over
and machine the back of the headstock to the proper thickness,
and parallel to the face.
- Carefully mark the position of the holes and bore the three
holes for the rollers of the tuners from the sides. It is advised
that you attempt to be as accurate as possible and measure to the
1/1000th of an inch. It is also
recommended that you place another piece of wood on the opposite
side where the tool will break through to avoid splintering, or
to machine the holes from each side instead of all the way
across. Do not burn the wood with dull bits. Bevel the edge of
the holes for proper clearance of the tuner parts. Check for
proper fit and then drill the small screw holes which will later
hold the tuners in. Use caution that you do not drill to deep and
if possible use your milling machine to ensure the depth is
correct. (If you drill to far, then the screw holes will show on
the inside of the string stores, so be cautious as a depth of a
quarter of an inch is all the way through!)
- Clamp at an angle and then cutout the string ramps exactly as
wide as the string stores will be.
- Reclamp the stock to mill out the string stores. You should
have noted that the cuts will have a better finish in one
direction compared to the other direction of your milling. Mill
in the direction (referenced to the rotation of the bit) which
does not tend to splinter the wood, that is, mill so that the
cutter is rotating the same way as the wood is moving as if the
cutter were pulling itself into the wood. Use light cuts and
repeated passes and as you approach your marks take the time to
measure untill you are shaving just 0.001 inches in a pass. You
may also cut the small notch at the top of the headstock for the
inlay at this time as this will result in its being cut most
accurately. Cut the end of the headstock also at this time. Using
a special cutter, radius the three outside edges of the headstock
and then do the same for the edges of the string stores with a
smaller bit. Use caution so that you do not run the bit into the
string ramp, and finish with a hand blending of this radius on
the string ramp toward the nut where there is insufficient
clearance to machine. Your headstock cuts should now be
complete.
- Clamp the neck flat on its fretboard (back of neck is up)
and cut out the tang to
its proper width and depth. Watch that you do not cut into the
fretboard portion of the neck as the fretboard portion will need
to remain wider than than the tang at one end.
- Reclamp the neck to the proper angle for the neck's taper,
and face the back of the neck to the proper thickness from the
headstock to the shoulder just before the body. Make the
additional scarf cuts (not to finished size) along the necks
radius which will reduce the amount of hand work needed for the
final smoothing of the neck. I strongly recommend working these
cuts out on paper as well as marking the limits of the cuts on
the stock to prevent the error of over cutting.
- Flip the neck over and reclamp so that the side may be milled
to the correct angle. Mill one side, then clamp to the angle
required for the next side and make that cut as well.
- As a finishing touch I like to mill a couple of spots to
insert abalone dots on the side of the neck. I mark just the
seventh and nineteenth frets in this manner. Glue in these dots
as well as the headstock inlay at this time and let cure before
proceeding to sand the neck in the next step.
- Using files, belt sanders, and hand sanding and scrapping
techniques, gently shape the back of the neck until it is
perfectly radiused, using great care to ensure a smooth and
straight gliding of the performers thumb in concert. I used a
series of blocks shaped to the various proper radii and glued
sandpaper to them and then sanded length wise to prevent dips and
bumps. Heavy cardboard can be shaped to a proper radius and also
used as a sanding block. Proceed slowly and methodically taking
great care to make this as even, and as fluid a shape as
possible, (as ANY perceivable imperfection will be a distraction
to the performer.) You should work toward finer and finer sized
sand paper as you progress, and end with 1000 grit paper. I
prefer to use emery paper and wipe often with a damp cloth or
sometimes a bit of acetone as this helps keep the surface clean
and free from oils. You may elect to also sand or scrape the
headstock to blend the area where headstock and neck merge and
where the inlay was glued in. (The ends of the inlay should be
blended to the same radius as the edge of the headstock and made
level with the face of the headstock.)
- Luthiers usually make straight cuts across the fretboard for
the fretwire's tang to set into. This results in the ends of the
fretwire's tang showing on the side of the neck. While this is
okay with most, some (rarely on a classic guitar) add a layer of
binding to cover this. Binding in this manner will require
additional cuts to the neck where the binding will be and is
non-traditional in a classic guitar. It is more acceptable to cut
straight across and leave the ends visible than to hide the ends
behind some binding. But there is a better solution. Simply make
the cuts stop short of the edge of the neck and shape the ends of
the tangs to fit. Use a milling machine or other accurate device
to ensure that all cuts are precisely made whichever method you
use. If you choose to follow the plan you will first need to
construct a device to make these cuts as I did, or use a very
small bit and great patience in milling slots just short of
protruding through the side of the neck.
- As a string is stretched when fretted, the action (height of
the strings) must be taken into account in determining the
placement of frets. An action which is high will result in a
string stretching more thus sounding sharp (at a slightly higher
pitch.) Lower action than normal will result in the opposite
effect, the string sounding flat (lower pitch.) The diameter of
the strings will also effect the placement of frets as a larger
diameter string will bend with a larger radius, and a thin string
will bend more sharply. The mass of a string (expected to be
proportional to the cross sectional area of the string) will
effect how much tension is required to achieve a given tone at a
given length also. A good player may compensate for a flat tone
by pulling (using the friction of the string under their fingers)
toward the nut when fretting, or conversely, pushing toward the
bridge if the tone is sharp. (Many guitars have some provision to
correct this at the bridge but this is uncommon in a classic
guitar.) Strings change with wear and readily change in moisture
content (changing their mass as a result) over time, adding to
this problem of proper fret placement. It is therefore strongly
recommended that you not change these dimensions until you have
become experienced enough to make subtle corrections for these
factors. Accurate, detailed, notes and lengthy testing over the
production of several guitars may guide you in making changes in
string length and the positioning of frets.
- fret slotting tool...
- Cut the fret slots (using a thin rotary blade if possible to
be able to end the cut at the edge of the neck.) using the table
below as a guide. (on a milling machine it is a simple matter to
move the table (and neck) an exact amount from one cut to the
next.
- fret positioning table...
- Mask the neck so that JUST the fretboard is left exposed, and
then apply the aging solution to artificially age the fretboard
making it black in color. This process takes many hours and will
oxidize the red (iron) of the wood to iron oxide II (which is
black, not rust colored.) Use care that the solution does not get
on the wood in the wrong spots or it will leave black marks.
- aging solution...
- Before proceeding to insert the frets, I like to mask the
fingerboard to protect it. Leave a small gap in the masking where
the frets will go so that they may be set in flush with the
fretboard.
- Cut each individual fret to its proper length. Keep them in
an ordered row as you make them, so that they may be placed in
their correct fret slots and not get mixed up. You will need to
shape the ends of their tang to precisely fit the ends of the
fret slots. They may be hand shaped using files or ground with a
small hand held rotary tool grinder. A drop of thin cyanoacrylic
glue may be used in the slot to help them stay in, but have a rag
with some acetone handy to mop up any excess. If you do use glue,
you will need to work rapidly before the glue has had time to
polymerize (set.) Do one fret at a time. They may need a bit of
force to seat them flush, and they may be either tapped in using
a small block of soft metal to prevent hammer marks, or pressed
in using a clamp (again being careful to not dent them, or the
fretboard, or the back of the neck.) After they are all inserted
and the glue has set, then use a small file to radius the ends
making sure they have no sharp edges which could cut the player
or snag on clothing etc. Do not dress the frets at this time
except on the ends as just mentioned.
The Sides and Body
- Wenge (the wood chosen) is a hard wood with a rough mahogany
like texture and composed of light chocolate brown and black
alternating in the tight grain pattern. it is: brittle, porous,
easily splintered, hard, and has the density of ebony, but it
looks good. I laminated together the faces of two boards using
Marine Tex (aluminum filled) epoxy to create a single, thick,
composite, block from which I later cut the body and sides as a
single piece. Take great care in selecting the wood based upon
its visual attributes. Orient the grain pattern of the back to
best match and flow with the shape of the instrument.
- Machine this block to make the faces parallel and to the
proper thickness.
- Layout the outer edge outline of the body and the slot for
the neck tang by drawing lightly with a sharp white pencil.
Leaving a margin around the outside for later error correction (a
quarter inch should be plenty if you are accurate about your
work,) and cut out the rough shape (with a band saw or coping
saw.)
- This next cut (milling a slot for the neck tang) should be
done precisely as possible. Place the block in the milling
machine, mill the end of the block where the slot will come out
to a right angle to the slot if not already perfectly square,
then machine out the slot. You may continue your cuts slightly
past their ends to eliminate the two rounded corners which would
prevent the neck tang from fitting properly. The dimensions of
this slot should allow the neck to fit in perfectly with the
fingerboard, aprox. a quarter inch above the body, and with the
twelveth fret just at the end of the body (as in a standard
acoustic classic guitar.)
- Before proceeding with the machining of the body, it will be
helpful to have the top cut to size. Using the top for a
template, you may draw the lines marking the inner cut for the
insert of the top and then mark the outer cuts to define the body
shape. As these cuts are not done through precise geometric
measurements but by eye and hand, this order (slot first, make
the top next, use top as template for inner cutout of body) will
allow you to make the most even side wall thickness, tapering
slightly thicker towards the end of the guitar.
- Machine the body to allow the top to set in slightly above
flush. Machine the outside and radius the outside edges on both
front and back (stay away from the slot region and do it by hand
later, or wait and do all the radiusing by hand later.)
- With the help of a friend I held the binding in some steam
and bent it to match the shape of the top. A few inches at a
time, we glued the first (inner) binding strip all the way around
the outside of the top, adjusting with bends with steam only if
needed. The strip was glued flush (or slightly above) the top and
trimmed squarely at the slot. Using an accelerator with
cyanoacrylic glue and you will need little in the way of banding
to hold it while it is setting up. Let the glue cure a day and
repeat with the next (alternating color) strip of binding untill
all five strips are glued flush around the outside of the
top.
- Gently use this a a template to mark the body where it must
be further cutout to accommodate the binding now glued around the
top. Go ahead and mill or otherwise make this new cut so that the
top will again fit into the body. Be as accurate as possible so
that the seams will be flawless and not have gaps to be
filled.
- Glue the neck to the body and clamp. Be sure the end of the
tang fits snug to the end of the slot and that it is evenly
clamped along its length to mate perfectly with the body.
- Machine the body cavity from the top side to make the neck
tang flush with the rest of area previously cut out for the
top.
- You may delay the upcoming gluing processes (except the
gluing of the binding around the top) until all the parts are
machined (or cut to size.) This is a mater of personal choice,
and there may be advantages to either. (The body is easier to
machine without the presence of other parts but it may be more
difficult to precisely position the bridge and thus the holes
needed for the knobs etc.) If your top fits precisely and can be
held steady with clearance for borring the holes for the knobs,
and you are confident in your precision then you may do as I did,
and delay in gluing the top until you have completed the
machining of the body (to more easily machine the internal
cutouts for the wires from the topside of the body.)
- Glue the top into the body. Let cure. Machine the top flush
and sand to a final finish. (Any builder will tell you to scrape
the wood for the superb finish, so bear in mind that you are
creating a final surface and treat it accordingly. Go only in the
direction of the grain, never against it. Use almost zero
pressure and infinite patience for the finest surface.) While
this top may have little influence on the actual sound, its
appearance will have a great influence on the opinion of
guitarists as they expect a perfect finish on the finest of tone
woods in any quality handcrafted instrument. I select my spruce
with the straightest grain, spaced most evenly, (from an eighth
to a quarter inch apart) exhibiting the most and brightest cross
grain markings or spidering(?). This page has a photograph of a
top of mine as it's background (enlarged and tiled) as an
example.
- Machine the bridge from a block of Cocabolo ensuring yourself
that the layers of grain are NOT parallel to the top of the
guitar as this would weaken the string tie block structurally.
The grain pattern should be at a right angle to the pattern in
the top. (See the separate section on the bridge for details on
the machining.)
- This step should not be required if you have a truly flat top
and have machined the under side of the bridge flat as well.
Check the bridge for a matching fit to the top and precede with
the following only if there are gaps or unevenness which need
correcting. Sand the bottom of the bridge to match the top of the
guitar by placing a sheet of sand paper on the top of the guitar
(grit side up!) and using it as a sanding form or block, place
the bridge on it and sand with a short strokes in the direction
of the neck until it matches the top where it will be
placed.
- If the dimensions are unaltered (or altered properly,) and
cut to plan, then the sides of the guitar neck will be very close
to being parallel with the adjacent (outer) strings. Our bridge
should already have six small holes drilled in it where the wires
for the pickup will go through and we will now need some small
dowels (round toothpicks seem to work fine for this) which will
soon be placed through these holes and into matching holes about
to be drilled through the top. using light, easily adjusted,
clamps, position the bridge exactly and then using the six holes
as pilots drill six holes through the top (drill the outermost
holes first, and insert the dowels to help hold the bridge steady
as needed.) It may be wise to temporally place the nut, and
insert the tuners into the headstock and then string the outer
strings to visually check for proper alignment of the string as
it runs the parallel to length of the neck.
- Mask around the bridge as it sets there on the top. This
masking should prevent glue from getting on the top where not
desired. Wipe the wood with acetone, and using silicone on the
dowels and in their holes to prevent the glue from gluing in the
alignment dowels, glue the the bridge onto the top, clamp, and
wipe off any excess glue (with acetone if using a cyanoacrylic
glue. Use caution with the silicone and keep it and any transfered film
of it from your fingers or tools away from the wood as it will
prevent the finish from sticking also.) Let cure, then remove
the dowel pins (redrill the holes if
necessary so that the pickup will set in flush.)
- Using the bridge for alignment (a thin piece of tape may be
used to protect the surface of the bridge around the cut-outs for
the knobs) bore the holes for the knobs using caution and
planning to stop three eights (0.375) of an inch before going all
the way through the back. Fostner bits will work best for this
and the center of the bit can be ignored in reference to the
depth. (The outside of the bit should stop 3/8 of in inch short
of going through the back.)
The Top
The Bridge
The Knobs
The Back Cover Plate
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