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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. (Youíd 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. Thatís when itís 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 guitarís top bellies up around the bridge, and the neck-to-body angle changes. In extreme cases, the topís 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. Iíve heard it said at bluegrass festivals that older instruments that donít have a bit of bulge just donít have the tone either. There may be some truth to this statement, since a guitar that doesnít distort over time is probably overbuilt. But what weíre 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? Iíve seen a lot of guitars get diagnosed for resets that, in my opinion, werenít 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. Itís kind of like making a call for angioplasty versus a heart bypass operation--either way itís 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 "donít try this at home" category. Neck resets are standard procedure for the truly qualified luthier, but you donít 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 letís assume for now that the neck resets are to solve the problem of an action thatís 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 1Ė14 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, hereís what will probably happen to it.
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 Larrivťe 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 thatís 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 guitarís body.
There are a number of ways to actually remove the neck. I use a specially made jig that clamps to the guitarís 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.
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 itís 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 donít be surprised if your luthier calls for the full job.
This area of the fingerboard over the guitarís top is problematic for many traditionally built acoustic guitars, and a number of modern instruments, such as the Martin D-1 and Steve Kleinís 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 guitarís 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.
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