TOOL
Feeler gauge
The only honest way to measure relief and nut height.
| Range | 0.02 – 1.0 mm in a graduated set |
|---|---|
| Blades | Typically 13 to 26, on a pivot |
| Material | Hardened steel, marked in mm and inches |
| Use | Relief at the seventh fret; nut height at the first |
| Care | Keep clean and dry; blades bend easily |
| Reference | Bend a single blade for awkward angles |
| Relief target | 0.15 – 0.25 mm at the seventh fret |
|---|---|
| Nut clearance | 0.25 – 0.5 mm at the first fret |
| Method | Slide blades under the string until one lifts it |
| String state | At pitch, in playing position |
| Repeatability | Measure the same string each time |
| Price band | Low |
A feeler gauge is a set of thin steel blades of known thickness. It is how relief is measured — sliding blades under a string at the seventh fret until they just touch — and how first-fret clearance at the nut is checked.
The measurement is a go/no-go: the thickest blade that slides under without lifting the string is the gap. That makes it far more reliable than eyeballing a gap against a ruler.
At this stage
Relief is set before anything else in a setup, because nut height and action are both measured relative to a neck that is already in its final curve.
Suits these instruments
- All guitars and basses
Works with
- Action gauge
- Notched straightedge
- Truss rod
- Nut file set
- Feeler blades have sharp edges and bend permanently. Handle them flat, not by the tips.
- Do not force a blade under a string at pitch — it can lift the string off the nut.
Working notes
- Measure relief on the low E, then confirm on the high E. A twisted neck shows up as a difference between the two.
- Use the same blade set every time so your numbers mean something over months.
- A blade that slides under with no drag means you need a thicker one.
- Oil the pivot occasionally; a rusty feeler gauge gives false readings.
Related
Action gauge
Reads string height at the twelfth fret without arguing about it.
Notched straightedge
Reads the fretboard itself, not the tops of the frets.
String winder
Turns a fifteen-minute string change into five.
Capo
Clamps the strings at a fret — and shows up any setup problem.