TOOL
Nut file set
The slot depth sets the action at the first fret.
| Range | 0.010 – 0.056 in in graduated steps |
|---|---|
| Profile | Round-edged, tapered, with a safe cutting edge |
| Set size | Typically 6 to 10 files |
| Handle | Wood or composite, comfortable for controlled strokes |
| Cut | Fine, for controlled removal in bone or synthetic nut material |
| Substitutes | Feeler gauges and abrasive cord for small adjustments |
| First-fret clearance | 0.25 – 0.5 mm at the first fret |
|---|---|
| Slot width | String gauge plus a few thousandths |
| Slot shape | Round-bottomed, angled back toward the headstock |
| Depth check | Feeler gauge between string and first fret |
| Lubrication | Graphite or nut lubricant after cutting |
| Price band | Moderate to high for a full set |
Nut files are thin, round-edged files in graduated widths, matched to string gauges. They cut the string slots in the nut, and the depth of those slots sets the string height at the first fret — which is where most playability problems actually live.
A set covers roughly 0.010 in to 0.056 in so each string gets a slot of its own gauge. Filing a heavy string slot with a light file produces a slot that pinches the string and causes tuning instability.
At this stage
Cut the nut slots last, after the frets are level and the relief is set. The nut height is measured relative to the frets, so it cannot be right before they are.
Suits these instruments
- All fretted instruments
Works with
- Fret leveling file
- Action gauge
- Feeler gauge
- Truss rod
- Nut files are sharp and thin. Keep both hands behind the cutting edge and cut away from your fingers.
- Nut dust from bone is a respiratory irritant. Work damp or with extraction.
Working notes
- Cut a fraction too little, then test. It is easy to remove more and impossible to add back.
- Angle the slot down toward the headstock so the string breaks cleanly over the front edge.
- A sliver of string gauge held in the slot shows whether it is pinching.
- Graphite in the slot stops the string sticking and wandering out of tune.
Related
Fret wire
Nickel silver or stainless, and the crown shape decides the feel.
Fret slotting saw
One saw, one kerf, no second chances.
Fret press
Seats a fret evenly instead of hammering it in.
Fret leveling file
Makes every fret the same height, then gives the crown back.