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William Cumpiano's
String Instrument
Newsletter #1

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Eighteen

Resetting Guitar Necks: why, what for, and how

1998 William R. Cumpiano All Rights Reserved

Diagnosing a Reset

When a guitar is hard to play, the obvious course of action is to lower the string array a bit, laying it accurately just a bit closer to the frets. But often this is easier to say than to do. It may be as simple as twisting a bolt, or as extreme rebuilding the neck joint—resetting the guitar’s neck

The tricky part of deciding whether or not to reset your guitar’s neck, is that the major symptom of a bad neck angle – hard playing – is also a symptom of many other simpler problems. We could conceivably go to the considerable trouble of resetting a guitar’s neck, when indeed an acceptable solution for the perceived problem might be a minor adjustment and some light fretwork.

Even when the hard action is indeed, the result of a bad neck angle, sometimes there are ways to correct its ill effects by less drastic means. However, these may not always be appropriate to your particular guitar, or enough to resolve the problem completely.

So the most prudent course is to do attempt the simpler, less invasive adjustments to improve the instrument’s hard action, first. When all these are exhausted you may decide, happily, that you’re comfortable with the result (physically as well as financially), or to consent to open-neck surgery. The simpler recourses are as follows:

TRY THE TRUSS ROD

Before attempting other measures to make a guitar easier to play (often with the added bonus of improving its pitch accuracy) try adjusting the guitar’s truss rod. Tightening the rod’s adjusting nut can effectively lower the strings if their tension has, over time, caused the neck to flex up in a slight curve. In these cases, a dramatic improvement in playability can result from just a little tightening.

Of course, tightening the rod can’t change the neck’s angle! It can only straighten the shaft itself. Furthermore, the truss rod can only be adjusted to its optimum position – which may or may not be sufficient to remedy a hard-action problem.

The proper check for the optimum state of truss rod adjustment is to first tune the guitar accurately to concert pitch. Then, press the string down BEHIND the first fret (to eliminate the influence of the nut) and at the same time press the string down in front of the twelfth fret (to eliminate the influence of the saddle). By thus "filtering" out the nut and saddle, we can now focus our attention on comparing how straight the neck is – by directly comparing it to how straight the stretched string is – which is very, very straight.

GETTING RELIEF

When comparing the perfectly straight, stretched sting to the fretboard surface (the surface determined by the tops of all the frets), the difference shows up right in the middle as relief: that is, what actually needs to be adjusted by tightening or loosening the rod’s nut. No relief, that is, the string pressing directly on the frets in the middle, betrays either of two incorrect situations: a perfectly straight fretboard surface, or a fretboard surface which is bent back. A back-bent fretboard results from either an over tightened truss-rod nut, or (heaven’s) a permanently kinked neck-shaft.

What you want to see, however, is a minute amount of relief, or clearance, between the string and the fret right at the midpoint between the first and twelfth frets. If you think you can measure it, it should be:

Electric guitar: 1/64"

Acoustic guitar: 1/32" to 3/64"

Electric bass: 3/64"

With the strings up to tension, loosen or tighten the truss-rod nut until you achieve the proper relief. On double-rod systems, such as those on Guild jumbo 12-string guitars or Rickenbacker electrics (assuming they’re operating as they should) always aim for a hair more relief on the bass side. Turn the truss-rod nut no more than one-eighth to one-quarter turn at a time. In between turns, coax the neck in the desired direction by pressing it over your knee – firmly, but gently – once or twice before rechecking.

CLEARANCE AT THE NUT

Now that you’ve determined that the truss-rod adjustment is appropriate, and yet the action hasn’t improved enough, check the string clearance at the guitar’s nut. The best test is to press each string down, in turn, just beyond the second fret, and observe what the string does immediately over the first fret. While holding the string down in this way, observe the following:

When the string sits directly on the first fret, assume that the nut slot is too low. Hard picking on the open string will usually cause it to slap there. If there’s a hairs-breadth of clearance between the string and the fret, the nut height is optimal. Any greater discernible clearance is usually excessive. A further check is to tap ever-so-lightly on the string: so long as the string is high enough to audibly clink on the fret – why still maintaining clearance that is only just visible – then the nut is cut at the optimum height. No clink means the string is so low its touching, or so high that the a light tap will not succeed in bending the string far enough to hit the fret.

I repeat, don’t determine and cut the nut slot depth until AFTER you’ve adjusted the neck rod – or you’ll be sorry!

If too high, you must saw (with fine-gauged saws) or file (with nut-files) the slots down, a few strokes at a time, until they are right. Drat, sometimes that single extra stroke was one too many! In cutting the slot, the best way to proceed when you start to get close to the desired depth is to check it after each tool stroke. Make sure to angle your tool-stroke to yield a slot floor that is inclined relative to the fretboard but just about the same as the angle of the headstock or flatter– certainly not steeper.

<Sigh>If the nut slots are too deep, the nut must be shimmed or replaced – that is, if MOST of the slots are too deep. If just one or two are too deep, the slots can be spot-filled and recut in the following way:

SPOT FILLING A NUT SLOT

A too-deep nut slot can best be repaired by patting a bit of baking soda (Sodium bicarbonate), not baking powder, directly into it. Cover the filled notch with a fingertip and blow gently around the nut to clear away the excess soda particles littered about. There should just be a little filled plug of baking soda in the slot, but nowhere else.

Now open a container of cyanoacrylate. Be careful: if the tip is too beat up or if your coffee-crazed nervous system won’t let you dispense a single drop where you want it, DON’T try it. I have a big glob of old dried-out cyanoacrylate on my vise jaw where I practice dispensing small, single drops first before approaching somebody’s favorite guitar. If I can’t, I get a new dispenser, or I wait later in the day when I’m more up to it. A flood of cyanoacrylate just can’t be a good thing all over someone’s guitar neck. Okay, you’re forewarned: now let fall a tiny drop of cyanoacrylate glue – enough to just saturate the stuff in the slot.

Within moments, this simple filler compound will set up into a rock-hard plug of white stuff that can be sawn or filed into a new slot, at the precise depth you need.

Correct string-clearance at the nut can dramatically improve playing ease, not only at the nut, but considerably further down also. Often, it will also solve nagging intonation problems that previously seemed to defy any other solution!

Next time:

The guitar set-up procedure, which adjusts the action as optimally as possible short of a neck reset, continues with:

CUTTING THE SADDLE

THE BRIDGE RAMP REMEDY

CHECKING THE FRETBOARD INCLINATION

THE EFFECT OF SCALE LENGTH