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.
