Setting neck relief on a guitar is usually a pretty straightforward process, but a topic that inspires a lot of debate. Neck relief is the measurement of the “bow” in a neck, typically measured somewhere along the midpoint of the fret board. If a neck is perfectly straight, there is almost certain to be some string/fret buzz in the lower frets. Relief only affects the first few frets on the neck, buzzing above the 8th fret is related to string height (action).
There varying opinions on measuring relief, and our process is:
- Capo the first fret, and place your finger on the last fret
- On the 6th string, check the gap between the string and fret at the 8th fret
- Adjust to suit, we like ~.011 on guitars, and ~.018 on a bass
- If you don’t have a feeler gauge, a coated stock business card works as a general guide
- If the adjustment nut is at the headstock, when looking down the neck at the headstock turn the nut counter-clockwise to remove bow, clockwise to add bow
- If you have the adjustment at the heel of the neck, it’s the opposite
That’s pretty much it, and working in small increments (no more then a 1/4 turn without checking) it’s hard to do any damage.
Notice we said “adjust to suit” and by that we mean that there is not absolute correct amount of relief. Some players like the neck as flat as possible without string rattle, and that’s just fine. If you have a light playing touch, go as flat as you can.
Adding too much relief can be an issue, as large truss rod adjustments put additional stress on the neck. And high amounts of relief can affect intonation. To visualize the geometry: With more relief, the string length in relation to the fret board forms a bigger triangle, and the two lengths are less alike (from Middle School, the string is the hypotenuse and the fret board is the long leg of the triangle). The greater the difference increases intonation issues. So lots of relief serves no practical purpose, and if you still have fret buzz with a normal amount of relief, there are other issues.
Due to string tension, relief can vary with different brands of strings, and can even vary from side-to-side on the neck. If changing string gauges, check the relief to see if there is a need for adjustment. The same goes if you are going to a different tuning.
Some string gauge types can also put additional stress on the neck, such as a Light Top – Heavy Bottom set. With a LTHB set there is a greater variance in tension between the plain and wound strings, which can put some additional twisting stress on the neck. Some techs feel that LTHB strings are problematic and recommend sets with more even tension.,
Lastly, don’t use relief as a way to adjust string action. This is especially tempting with acoustic guitars as a way to avoid shimming or shaving the bridge saddle. A tiny tweak might be OK, but putting the neck under undue stress is not a good long term strategy.
There you have it: It’s not rocket science, and with a little practice any player can confidently and safely keep their guitar optimized for seasonal weather changes or using different strings and tuning.