Quick read: A Floyd Rose locking nut sits on a shelf milled into the neck. The shelf height — set by the original neck cut, the nut shim stack, and the locking nut clamp screws — determines how high the strings sit at the nut, which determines the open-string pitch and the first-fret action. When chord shapes sound sour after a string change or a saddle adjustment, and the saddle intonation is set correctly, the next thing to check is the locking nut height. The fix is usually a thin brass or wood shim under the nut to lift it 0.005-0.015 inches, or a careful filing of the shelf if the nut is sitting too high. Most owners pay a luthier $80-120 for this job. Done with feeler gauges, a Phillips-head, and a 1.5mm Allen wrench, it's a 30-minute job at the kitchen table. The trick is knowing when the height is wrong, and doing the change in 0.005-inch increments so you don't undercut the strings into the first fret.
| Symptom | Likely Cause | Fix |
|---|---|---|
| Open chords sound flat, fretted notes are in tune | Nut too low — strings buzz against frets | Add 0.005-0.010" shim under nut |
| Open chords sound sharp, first three frets play sharp | Nut too high — over-stretching strings to fret | Remove shim or file shelf 0.005" |
| Only B and high E sound sharp at first three frets | Asymmetric nut height — treble side too high | Shim bass side or file treble side |
| Strings buzz at first fret only, no other location | Nut too low on that string slot | Replace nut or shim entire nut up |
| Tuning drifts after dive bombs | Locking nut clamp screws too loose | Torque to 8 in-lb |
I've been playing the same Telecaster for almost 30 years and I'm not the obvious person to write about Floyd Rose maintenance. But I do setup work for friends and church-band players, and the locking nut height question comes up often enough that I wanted to write down what I've learned doing it on Charvels and Jacksons over the years. The procedure is approachable. The tools are cheap. And paying a luthier $100 every time the nut needs a 0.005-inch shim is the kind of thing that keeps players from owning their instrument — they're afraid of the part of the guitar that's too precise to mess with, and they pay someone else to do work they could do themselves.
Why the Nut Height Matters
The locking nut on a Floyd Rose is a flat brass or steel block with three string-pair slots cut into the top. The nut sits on a shelf that's milled into the back of the neck at the headstock end. The shelf is flat, the nut is flat, and the strings ride across the top of the nut at whatever height the nut shelf puts them at.
The string action at the first fret — measured as the gap between the bottom of the string and the top of the first fret — is determined entirely by the nut shelf height. There's no bone or graphite nut to file down for height adjustment, the way there is on a regular guitar. The whole nut moves up or down together, by shimming under it or by filing the shelf.
Open-string pitch and first-fret action are both functions of how high the strings sit at the nut. When the nut is too high, you have to stretch the string to fret it at the first fret — which raises the pitch of the fretted note relative to the open string, and produces sour chord shapes anywhere in the first three frets. When the nut is too low, the strings buzz against the first fret and the open strings sound flatter than they should because the string isn't fully clearing the fret edge.
The shelf height is set at the factory and most Floyd-equipped guitars never need adjustment. But over years of string changes, neck adjustments, fretwork, and the occasional fall off a guitar stand, the geometry shifts. By the second or third truss rod adjustment a guitar gets in its life, the nut height is often wrong by a few thousandths of an inch — enough to cause sour chord shapes that no amount of saddle intonation will fix.
How to Tell the Nut Height Is the Problem
Before you pull the nut off, make sure the saddles aren't the actual issue. Run through this diagnostic in order:
- Tune the open strings to pitch with a strobe tuner. If you don't have a strobe, a Polytune or Snark in fine-tune mode is close enough.
- Fret the low E at the 12th fret. It should read in tune to within 1-2 cents of the open E. If it's off by more than that, the saddle intonation is wrong — fix that first.
- Repeat for the other five strings. Each fretted 12th-fret note should match its open string to within 2 cents.
- Now play an open A chord. If the chord sounds sour even after the 12th-fret intonation is dead-on, the nut height is the next thing to check.
- Play an open D chord, then a fretted F at the first fret. If the open chord rings clean and the F is sharp, the nut is too high. If both sound flat and you hear fret buzz on the F, the nut is too low.
The asymmetry test catches the most common version of the problem. Play an A chord, then play a Bm barre at the second fret. If the open A is sour but the Bm is clean, the issue is at the nut. If both are sour, the issue is somewhere else — saddle intonation, neck relief, or fret wear.
What You'll Need
The kit is small and cheap.
- A 1.5mm Allen wrench for the locking nut clamp screws
- A Phillips-head screwdriver for the nut mounting screws
- A set of feeler gauges with 0.005, 0.010, 0.012, and 0.015 inch leaves — Hagstrom or Mitutoyo, $15
- Brass shim stock in 0.005, 0.010, and 0.015 inch thicknesses — StewMac sells this in a $12 sampler
- A clean, lint-free rag
- Optional: a small needle file for filing the nut shelf if shimming isn't the right move
The brass shim stock is what most luthiers use because it's stable and doesn't compress over time. A scrap of business-card stock works in a pinch but compresses and slips, so use brass if you can.
The Procedure
This is a 30-minute job done carefully. Don't rush.
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Tune the guitar to pitch and unlock the locking nut. Loosen the three locking nut clamp screws on top of the nut with the 1.5mm Allen wrench. Just unlock them — don't remove the screws.
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Detune the strings until they're slack. Loosen the fine tuners on the bridge first, then loosen the tuning machines until each string has visible slack. You don't need to remove the strings — they can stay in place across the slack nut.
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Lift the strings out of the nut slots. Each string comes out of the nut without removing it from the bridge. Lay the strings carefully off to the bass side of the neck so they don't kink.
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Remove the nut mounting screws. There are two Phillips-head screws on the back of the headstock that hold the nut to the shelf from below. Remove them and put them in a small dish so they don't roll away.
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Lift the nut off the shelf. It should come up cleanly. Note any existing shim stack underneath the nut — write down what's there so you can put it back if your adjustment doesn't work.
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Measure the current first-fret action with feeler gauges. With the strings still in approximately the right position over the neck (you can hold them there with your free hand), slide a feeler gauge between the low E string and the first fret. The target for most setups is 0.010-0.012 inches at the bass strings and 0.008-0.010 inches at the treble strings. If you're outside this range, you know which direction to move the nut.
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Add or remove shim material. To raise the nut, slide a brass shim onto the shelf before placing the nut back down. Start with the smallest shim that addresses the problem — usually 0.005 or 0.010 inches. To lower the nut, remove an existing shim, or if no shim is present, you'll need to file the shelf (see the next section).
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Re-seat the nut and reinstall the mounting screws. Tighten the screws snug but don't crank them — you're holding the nut down against the shelf, not crushing the shim.
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Lay the strings back into the nut slots. Each string goes back into the slot it came from. The slots are pre-cut and don't need filing — that's the whole point of a locking nut.
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Bring the strings up to pitch with the tuning machines. Don't lock the nut yet. Tune to standard with the machines.
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Re-check the first-fret action with feeler gauges. If you're in the 0.008-0.012 range across all six strings, you're done. If not, repeat the shim adjustment — it's better to do this in two passes than to overshoot.
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Lock the nut. Once the action is right, torque each clamp screw to about 8 inch-pounds. Hand-tight with a 1.5mm Allen wrench is approximately right — you should feel the screw bottom against the clamp pad without forcing it. Over-torquing strips the screws over time.
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Fine-tune at the bridge. Lock the nut, then bring the strings up to final pitch with the bridge fine tuners. Play a few chord shapes. If they sound right, you're done.
When You Need to File the Shelf Instead of Shim
Sometimes the nut is too high and there's no shim to remove — the shelf was milled high at the factory or by a previous tech. In that case, you have to file the shelf down. This is more careful work because you can't undo it.
Use a fine needle file with a flat surface. File the shelf in 0.002-0.003 inch increments — barely a few passes — and re-measure with feeler gauges after every adjustment. Take material off the entire shelf evenly. The goal is to lower the nut without tilting it.
If you've never done this before, this is the step where I'd suggest paying a luthier the first time and watching how they do it. The shimming step you can do yourself with no risk. The filing step is reversible only by buying a new shim stack tall enough to compensate for the over-filing — and that's a frustrating place to end up.
What I've Learned Doing This for Friends
Most of the locking nut height problems I see come from one of three causes:
The factory shelf was off by a few thousandths. Charvel and Jackson production runs vary, and a guitar that left the factory with a nut shelf 0.003 inches too low will play fine for a year and start sounding sour after the first truss rod adjustment changes the relief geometry. This is the most common case — a one-time 0.005-inch shim fixes it for the life of the guitar.
A previous string gauge change changed the equilibrium. Going from 9-42s to 10-46s changes the string tension, which changes the neck relief, which changes the effective nut height because the nut-to-first-fret geometry is now different. If a guitar that played fine on 9s starts sounding sour on 10s, check the nut before you blame the strings.
Someone over-torqued the clamp screws. This crushes the brass nut over time and lowers the effective string height by 0.001-0.002 inches per year of over-torquing. The fix is usually replacing the nut entirely — a $40 part — and torquing the new clamp screws correctly. Don't crank the locking nut clamps. They don't need to be tight; they need to be firm.
For a fuller breakdown of the related Floyd Rose maintenance procedures, our first-time string change guide covers the entry-point procedure, and our intonation walkthrough covers the saddle adjustment that should be ruled out first.
When to Just Pay the Luthier
There's nothing wrong with paying a luthier for this. A good one will charge $80-120 and do it right in 20 minutes. The reason to learn it yourself is the same reason to learn to change your own oil — not because you have to, but because the next time you notice the chord shape sounding sour, you can fix it that night instead of waiting two weeks for a tech appointment. For a player who gigs every weekend or tours, that's the difference between playing a sour rig and playing a clean one.
If you're not comfortable with the file-the-shelf step, do the shim adjustment yourself and take the guitar to a luthier the first time it needs filing. Watch them do it. Do it yourself the second time.
The locking nut height isn't the most common Floyd Rose maintenance question — string changes and intonation come up more often. But it's the one that explains the symptom most owners can't diagnose: the guitar is in tune at the 12th fret and still sounds wrong. The nut shelf is the missing piece, and now you know how to find it.
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