Guitar setup: how to repair a faulty guitar nut

We cannot overemphasise the importance of a guitar’s top nut. Most players assume that little strip of plastic, bone or brass is just there to keep the strings in the right place. There’s more to it than that.

A poorly cut and set-up top nut can cause bad intonation, string buzz and affect the playability of the first few frets of your guitar.

So, while there are other possible causes of string rattle, we’re going to concentrate on possible nut problems in our guide. Let’s get on the case.

If you’re a guitar maintenance novice, the top nut sits at the top of the fingerboard at the headstock end of your guitar (shown above). Nut ‘slots’ are the gaps that each string fits into.

Inspect the top nut. The nut slots should be high enough to allow the string to clear the 1st fret when played open, but low enough to make the string easy to fret.

If any of the nut slots are too low, allowing the string to rattle on the 1st fret, you will either have to replace the nut or rebuild and recut the slots (see step 8).

Nut slots should hold a guitar string firmly in place without ‘pinching’ it. If the slot is too narrow it can cause tuning problems. If it’s too big it can cause open strings to buzz.

To check if a string is rattling in its slot, push the string sideways behind the nut with one hand then pluck it open with the other. If the buzz disappears, you’ve found the problem.

Check for cracks in your top nut. Detune the strings and lift them out of their slots, and look for any cracks in the nut. If you find any, the nut will have to be replaced.

With the strings out of the way, look at the bottom of the slots. They should be smooth and level. If they look rough, clean them up with a nut file or a piece of light sandpaper.

If the slots in your nut are too big or cut too low, you can fill them in with superglue and recut them.

This takes a steady hand and lots of patience. Get your safety goggles ready…

The first step in rebuilding the slots in your nut is to protect the guitar’s finish. Cover the areas around the top nut with a suitable masking tape, as shown above.

Dip the edge of a piece of paper into some superglue then carefully feed it into the nut slot. Allow the glue to dry then repeat the process until the slot is filled. You can now re-cut the nut slots.

You need nut files to cut the slots properly. At about £100 a set they’re not cheap, but they will give you a pro result. We got ours from Stewart-MacDonald.

Carefully cut the slot using your nut file. Pop the string back in frequently until you get the correct height and make sure the bottom of each slot is flat to prevent buzzing.