Hi fellow muso's
Even though your average nut is simply a narrow piece of bone or plastic with six slots in the top, it is a vital part of a guitar that affects the instrument's overall playability and sound.
Generally speaking, there are two main problems with nuts. Either the nut slots are too shallow, or they are too deep. The solution to slots that are too deep is simple, but radical - remove the old nut and replace it! What happens in this case is that the deep slot makes the open string contact the first fretwire and produces an annoying and unmusical sound. All that can realistically be done, in the case of a standard plastic or bone nut is to replace it - not an easy task and one outside the scope of this article. You see, nuts are bought as blanks and need shaping and profiling like the original. They aren't bought ready-shaped, I'm afraid! If you find that your locking or roller nut is too low, you can usually buy shims to raise it. If not, you can make your own, although you will have to experiment with different materials and the thickness thereof.
The most common problem is nut slots which aren't cut deeply enough. This is a problem that you particularly find with cheaper guitars, although even my Les Paul, which cost not far off a grand (£1000), needed some work on the nut when I bought it. If the slots aren't cut deeply enough, the string feels very high off the board when playing open chords and notes on the first few frets. This will also cause intonation problems. The watchword here is caution. If you take the slots down too deeply, then you'll have to replace the nut.
So, if you need to deepen the slots in the nut, you will need a flat needle file with a "V" profile, and an Exacto saw or what I use, a small piece of junior hacksaw blade with the set knocked out. See the tools article for photos and more details.
With the guitar flat on its back and resting on a soft surface- a piece of carpet on a table is ideal - get some masking tape and stick a couple of layers of this on the fretboard in front of the nut and on the headstock behind the nut. It's possible and, indeed, essential to do this with the strings on. As you work on each slot, just slacken the string slightly and pop it into an adjacent slot.
As a rule of thumb, the wound strings need about half their diameter's clearance between the underside of the string and the first fret, whilst the plain strings require a full diameter. If you can't do this by eye, use a feeler gauge. In time, you'll come to rely on your own judgement.
The slots need to be filed sufficiently wide enough so that the strings don't "bind" in them. This is important, otherwise bends and trem bar use will put the strings out of tune if the slot walls don't allow the strings to return to where they were before you moved them. On the other hand, if the slot is too wide, the string may move from side to side in it as you bend or move the string in any way. The note may sound rather dull, and you may even be able to hear the string rubbing against the bottom of the slot - nasty! Also, the slots need to be filed so that they run at an angle which descends towards the head end. This way, the string has a sharpish edge on which to rest in the slot, giving a cleaner note at this "break" point, and, besides, the scale length is calculated from the front of the nut, ensuring the correct intonation of each string.
Now, to the nitty-gritty...
Check the string's clearance between the underside of it and the first fret. If it seems OK, leave it. If it seems too high, slacken off the string slightly and park it in the next slot. Take the file and gently place it in the slot. File gently, backwards and forwards - remembering to keep the tool angled down towards the headstock and the tip of it away from the headstock surface. Pop the string back in the slot, return it to pitch and check the first fret clearance again. If it seems OK, go on to the next string. If not, slacken the string and repeat the operation. I can't emphasis enough the need to file away only a little of the nut at a time. The difference between a well-cut nut slot and one that's too deep is measured in thousandths of an inch. Too much and you're into new nut territory - a lot of hard work if you do it yourself, and a hefty bill if you take it to a tech. You may need to keep filing, retuning and checking quite a few times. That's fine - just take it slow and easy.
The actual depth of the nut - not just the slots themselves - is important too. The strings should not be buried in the slot. Rather, the wound ones should sit with about half their diameter in the slot, whilst the plain ones should have about their whole diameter in there. So, you may need to remove some nut material from the upper surface. Just take care not to remove too much so that the strings pop out of their slots when you're playing. It'll mean a new nut time if that happens. Now's the time to get rid of any sharp corners at the ends of the nut, too.
In the couse of playing over the years, nut slots can become worn. If you notice a sudden tendency for the open strings to start buzzing on the first fret, and you can't see any other cause, this may be the problem. As you wind the strings and use the trem bar, they will gradually wear away the bottom of the slots. The only practical remedy, then, is to install a new nut. I have tried experimenting with various materials to fill slots that are too deep. Dust made out of the original nut material mixed with superglue seems to work the best, but this is really only a temporary measure at best.
As I said above, you can buy nut blanks and replace the nut yourself, but it is a lot of hard work - time-consuming and very precise. I've done it to my guitars when necessary, but if you're in any doubt as to your ability to do this job, my advice is take it to a guitar tech.
Now that your nut is sorted out, you should check the intonation again, which may have altered slightly. You see, one small adjustment to one factor that affects the action and playability of the guitar will almost certainly mean that the other factors will need checking again. So, taking the main factors as nut, trussrod, intonation and bridge height, you'll find yourself shuttling between all these after you've addressed one of them. There's a lot of very subtle interaction going on between these factors that you must recognise if your set up is going to be a good one.
Fenderbender
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