There comes a time in the life of a steel-string guitar when
the years of string tension have finally distorted the geometry of the
instrument beyond what a simple adjustment of the action can fix. (You’d
get bent, too, if you had to carry 150 to 180 pounds of tension around
for 30 or more years!) As the various pieces of wood that make up the
top, sides, and back of the guitar slowly deform, the string action rises
ever higher, until the guitar gets to the point where reducing the height
of the bridge and/or saddle is no longer a reasonable way to regain playability.
That’s when it’s time to get a neck reset.
Many acoustic guitars are built with a bit of "extra" bridge
and saddle height so a luthier can compensate for the distortion by
lowering the saddle and/or shaving down the top of the bridge. Most
steel-string acoustic bridges are about 1/4 to 5/16 of an inch high,
with the saddle protruding about an eighth of an inch. If the action
can be made right without deviating too far from these measurements,
then you might be able to avoid a neck reset without compromising tone.
The string tension generally results in at least two visible effects:
the guitar’s top bellies up around the bridge, and the neck-to-body
angle changes. In extreme cases, the top’s upper bout can also start
to cave in. A certain degree of top belly is considered normal for older
steel-strings. Many of the best prewar Martins, for example, look a
bit pregnant. I’ve heard it said at bluegrass festivals that older instruments
that don’t have a bit of bulge just don’t have the tone either. There
may be some truth to this statement, since a guitar that doesn’t distort
over time is probably overbuilt. But what we’re really concerned with
here is neck angle, and that is where we have the opportunity to make
corrections, including compensation for top belly.
TO RESET OR NOT TO RESET
How do you know if a neck reset is indicated? I’ve seen a lot of guitars
get diagnosed for resets that, in my opinion, weren’t necessary. I tend
to work on the conservative side of things: if the action can be made
decent without shaving the bridge too low, I try to avoid the reset.
It’s kind of like making a call for angioplasty versus a heart bypass
operation--either way it’s a big deal, but one method is a bit less
invasive.
If your guitar does need a neck reset, this repair is definitely in
the "don’t try this at home" category. Neck resets are standard
procedure for the truly qualified luthier, but you don’t want someone
doing his first reset on your vintage dreadnought!
Although 95 percent or more of neck resets are executed to correct
for bellying and forward neck shift, the occasional reset is called
for to correct the opposite condition, where the action is too low even
with a very high bridge. This sometimes happens when an old guitar made
for Hawaiian lap-style playing, like a Roy Smeck or a Martin Hawaiian,
is converted to Spanish style. But let’s assume for now that the neck
resets are to solve the problem of an action that’s too high on an instrument
whose bridge is too low.
Done right, a neck reset will not only dramatically improve the playability
of your precious instrument, but can also bring out the tone of the
guitar. This is because as the guitar ages, the tonal properties of
the wood get better while the neck-angle-to-body geometry gets worse.
When you reset the neck, you can have the best of both worlds--great
aged wood and proper geometry.
How does a reset affect value on a vintage instrument? First, a good
neck reset done by an experienced luthier can be virtually undetectable
on guitars whose necks and bodies were lacquered before final assembly.
Second, a reset can make the difference between a great playing instrument
and a wall hanger. As far as "vintage value" goes, I would
much rather have a 1938 Martin herringbone D-28 with a good reset than
the same guitar with a shaved bridge and bad action. I think that most
vintage guitar dealers would agree with me on this. Steel-string guitars,
as we know them, have barely been around for 100 years, so we are just
now seeing the effects of age and use on them. Violinists are used to
the idea that their instruments need rebuilding every now and then,
and guitarists finally seem to be coming around to that attitude.
To determine whether or not a guitar needs a reset, I put a straightedge
on the top of the frets and slide it down to the bridge. If there is
no drastic rise in the fingerboard between the 12th and 16th frets,
the straightedge should just about graze the top of the bridge ahead
of the saddle or hit it no more than about .015 inches below its top.
(This applies only to unmodified bridges and assumes that the bridge
height was correct for the type of guitar in question.) If the straightedge
meets the bridge any lower than this, the instrument probably needs
a reset.
If you sight the tops of frets 1–14 and see that an imaginary line
following that sight line will land in the body of the bridge, then
yes, you need a neck reset. Some repair techs will pull frets, plane
the fingerboard, and refret to try to take care of fingerboard rise,
but this is only effective in mild cases and does not affect neck-to-body
angle, which may also be incorrect.
Neck reset techniques have come a long way in the past 25 years, and
luthiers share techniques freely. Gone are the days of guitar-making
secrets passed down to the few and withheld from the many. If you bring
your guitar in for a reset, here’s what will probably happen to it.
DOVETAILED NECK
On guitars with dovetail neck joints, I take out the 15th fret or whichever
fret is right over the dovetail joint. The fret should be heated to
make removal easy and to avoid fingerboard chip-outs.
If the neck was joined to the body before finishing (which is common
with Gibsons, Guilds, and Gibson-made Epiphones, for instance), the
finish needs to be carefully cut at the sides of the heel in order to
allow the neck to slide free. This is a tricky procedure that makes
it much harder to do inconspicuous resets on guitars made this way.
Martin, Santa Cruz, and Larrivée guitars, among many others,
have their necks glued on after finish, making resets much easier to
hide.
The next step is gently heating the part of the fingerboard that’s
over the body to soften the glue joint with the top. Applying lemon
oil to the fingerboard will help transfer the heat through the board
and prevent excessive drying and cracks. The idea here is to preserve
the structural integrity of the fingerboard by not having to cut through
a fret slot. I then loosen the fingerboard over the body by carefully
slipping in a sharpened blade that looks much like a very thin, wide
oyster knife. A bit of spray-on dry lubricant makes this step go easier.
Next, two holes are drilled through the fret slot down into the dovetail
area. A basketball pump needle attached to a tube and steam source (I
use a cappuccino steamer) introduces steam into the dovetail joint.
The steam heat softens the glue in the dovetail, allowing the neck to
be removed from the guitar’s body.
Photograph
by Frank Ford
There are a number of ways to actually remove the neck. I use a specially
made jig that clamps to the guitar’s body and has a screw that bears
against the heel cap. After an average of two to five minutes of steam,
the neck is ready to slide off, usually clean as can be. If there is
any chipping of wood in the dovetail, I glue the pieces back immediately
with aliphatic resin glue. Then I clean out any old glue, because new
glue wants to stick to wood, not old glue.
I then carefully recut the surface of the neck heel that contacts the
sides of the body on a taper from just under the fingerboard (where
nothing is generally taken away) to the heel cap, establishing a new
angle for the neck to be set to. This is usually done by hand, though
luthier Steve Crisp has designed a clever jig into which the neck can
be clamped with a tilting table to guide an offset router, which perfectly
recuts the surface of the heel. Either way, the new angle is cut and
then the dovetail is shimmed with veneers and refit to match the dovetail
in the body.
BOLT-ON NECK
Many modern builders, Bill Collings, Dana Bourgeois, and Bob Taylor
included, have chosen to bolt on the necks of their guitars, both as
a manufacturing convenience and a way to make future neck resets much
easier on the guitar and the luthier. As Taylor has pointed out, with
a traditional dovetail joint, eight surfaces have to match up perfectly;
while with a bolt-on, the number is four, and only two of these have
to be shaved to change the neck angle.
To reset a bolt-on neck, you only have to free the fingerboard and
then release two bolts, which are usually hidden under a label on the
neck block. Then it’s just a matter of shaving the heel surface to get
the new correct neck pitch and rebolting the neck while regluing the
fingerboard to the top. Here too, the Crisp jig makes short work of
cutting a new surface.
Whether your guitar has a dovetailed or bolted-on neck, a reset will
generally change the plane of the fingerboard where it makes the transition
from neck to top. If the fingerboard drops off drastically at the neck
joint, it may be necessary to install a tapered shim to raise its end,
and bound fingerboards complicate the procedure. If the fingerboard
takes a rise over the body, the fingerboard will need to be planed level.
Many repairers will not even do a reset without also doing a refret
in order to correct the fingerboard surface, especially in the neck
joint area. Sometimes we get lucky and no refret is needed, but don’t
be surprised if your luthier calls for the full job.
This area of the fingerboard over the guitar’s top is problematic for
many traditionally built acoustic guitars, and a number of modern instruments,
such as the Martin D-1 and Steve Klein’s guitars, attempt to beef up
the support of the top under the fingerboard to alleviate these problems.
Bob Taylor has written about how humidity changes can cause havoc in
the neck-to-body fingerboard transition; the top rises and falls as
it expands and contracts in response to the rise and fall of ambient
humidity. The fingerboard extension, being glued to the top, rises and
falls too, and this can cause the action to go up and the strings to
fret out at the same time. Try to keep your guitar safe from drastic
humidity changes, and understand that if you have your action set up
in either very high or very low humidity conditions, it will probably
change drastically. Thus it is best to reset a neck under humidity conditions
of around 43 to 48 percent.
After your guitar’s neck has been reset and the instrument has been
set up, you should experience the best of both worlds: the playability
of a new neck angle and the sound of well-aged tonewood. Enjoy it.
Excerpted from Acoustic
Guitar magazine, November 1997, No. 59.
