TOOL
Truss rod
The adjustment that decides relief — and it only works if it was installed right.
| Types | One-way (compression) and two-way (dual action) |
|---|---|
| Common lengths | 380 – 500 mm |
| Adjustment access | Headstock, heel or soundhole |
| Nut size | 4 mm hex, 5 mm hex or 1/4 in, depending on the rod |
| Sleeve | Rod wrapped in tape or sleeved to stop rattles |
| Channel | Straight, deep enough to clear the rod fully |
| Relief target | 0.15 – 0.25 mm at the seventh fret |
|---|---|
| Adjustment increment | Quarter turn at a time |
| Settle time | Allow the neck to settle between adjustments |
| Rod material | Steel, sometimes with a brass anchor |
| Channel fit | Snug; a loose channel lets the rod rattle |
| Price band | Low to moderate |
A truss rod is a steel bar set into a channel in the neck that counteracts the pull of the strings. One-way rods only pull the neck backward. Two-way rods adjust in both directions, which means they can also correct a neck that has gone into a back bow.
The rod has to be installed in a channel that is straight and correctly deep, with the rod wrapped or sleeved so it cannot rattle. A rod that buzzes inside the neck cannot be fixed without removing the fretboard.
At this stage
The rod is installed before the fretboard goes on. Once the board is glued, the rod is sealed in, so the channel and the rod have to be right the first time.
Suits these instruments
- Steel-string acoustic
- Electric
- Bass
- Archtop
Works with
- Maple or mahogany neck
- Notched straightedge
- Fret leveling file
- Action gauge
- Do not force a truss rod nut. A seized rod can snap, and a snapped rod means removing the fretboard.
- Adjust with the instrument supported and the strings at pitch, or at slack, but be consistent — the two give different readings.
Working notes
- Wrap the rod in tape or fit a sleeve. A rattling truss rod is a job that cannot be repaired in place.
- Wax the threads so the nut turns smoothly years later.
- Mark the neutral position when you install it, so future adjustment starts from a known point.
- Quarter turns only, and let the neck settle before measuring again.
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.