At a jam session a while back, an aquaintance and I were disscussing guitars. He picked up his guitar and looked knowingly down the neck and proclaimed, "I need to get the neck fixed, it's warped a bit." I replied, "maybe it's the good kind of warped." Utterly bewildered and amazed, he stared with complete conviction, that, I must be "one string short of a set." It seems that most pickers think that anything less than an absolutely straight neck is unacceptable. Actually a warped guitar neck is bad, if it's truly warped. But what many pickers mistakenly assume is a warped neck, is in reality "neck relief." A perfectly straight neck will almost always indicate an improperly adjusted instrument. A slight curvature of the fingerboard is essential for a soft action when playing in the upper positions of the fingerboard. The extreme can, of course, cause buzzes, rattles, and scale inaccuracy.
The diagram below should help to clarify the physical actions that occur when a string is plucked. A guitar maker or repairman will intentionally compensate for this action by adding neck relief.
The open position is where the relief is most important and is confined to the area between the nut and 12th fret. Past the twelfth fret, the fingerboad is straight and relief inconsequential because the strings swing less widely in that area. The amount of relief required in the higher positions is so small that it may be ignored. To perform a simple check for the correct amount of neck relief, site down the neck from the nut toward the bridge. With strings at full tension you should see a slight curvature along the fingerboard with the apex 1/64 to 1/32 of and inch below the first and twelfth fret. This can vary due to the individual peculiarity of an instrument such as string weight, scale length, etc. A more involved method of testing is to deliberately cause a string to buzz by extra hard plucking.
1...If a buzz is produced from all of the frets, then the amount of neck relief is probably correct. All that's needed in that case is a small amount of bridge adjustment to suit the individual style of playing.
2...An insufficient amount of relief or a warped neck will cause buzzes in the lower positions nearer the nut.
3...String buzzing in the higher positions can indicate too much neck relief or a warped neck. Remember though, string tension can cause the neck to pull upward.
4...If you encounter no buzzing at all, then the bridge may be lowered if you prefer a lighter action.
There is no "fits all" adjustment due to the varying styles of playing and different types of music. However, the table below reflects standard guidelines.
NOTES
Measurements are based on medium gage strings.
Light strings and light playing require less relief and heavy strings and heavy playing need more relief.
Short scales need less relief and long scales require more.
More relief is needed if the emphasis is on open strings and lower positions, while emphasis on upper positions require less relief.
| MEASUREMENT IN INCHES AT FIFTH FRET |
|---|
| Guitar Type | Treble | Bass | Notes |
| Steel String Acoustic | 1-2/64 | 2-3/64 | This setting is correct for fingerpicking. Lead players may need less relief while heavy bass rhythm may need more. |
| Steel String Electric | 1-2/64 | 2-3/64 | Slightly more for rhythm, less for lead players. |
| Rock & Roll Electric | 0-1/64 | 1-2/64 | Upper position string bends are best with this setting. |
| Classical or Flamenco | 1-2/64 | 2-3/64 | Most scale lengths and string tensions fall within this setting and is suitable for most flamenco & classical guitars. |
| Electric Bass | 2-3/64 | 3-4/64 | Appropriate for all long scale and Fender basses. Short scale basses increase relief slightly. |
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