
Originally Posted by
Simon Barden
From a theoretical point of view, the minimum nut height above the fretboard would be 1st fret height + 0.02" (for Stewmacs' recommended bottom E clearance) + (Bottom E string thickness/2), for a nut where the nut grooves were the minimum of half a string's height. Working in both mm and inches, an example would be a fret height of say 1.5mm/0.059", a bottom E clearance of 0.51mm/0.02" and a half bottom E string height (of a 0.054" string) of 0.67mm/0.027", giving a total of 2.69mm/0.106". Rounding up for convenience,that's 2.7mm or 0.11" above the fretboard for this example.
The high E side would need less fret clearance, so around 0.25mm/0.01" and the slot height need only be say 0.18mm/0.005", giving a total minimum height above fretboard of 1.93mm/0.074". Rounding up a bit, that's 2mm/0.08".
Rather than the minimum half a string's depth, I prefer almost a full string's depth for my nut slots, to help stop strings popping out under string bending near the nut. So I'd end up with a slightly higher nut.
This is all theoretical, because depending upon the way your neck is set in terms of relief, you may need a bit more height above the 1st fret, or you may get away with slightly less. Which is why setting the nut slot heights should be done after setting the neck relief and the bridge height, not before. It's also why I'd prefer to cut the nut slots first, then lower the height of the nut by filing, sanding and polishing to suit. However, this method should give you a rough idea of how much lower the overall nut height can be than you have now.
It may be easier to reduce the overall nut height first, when it's off the guitar, to something approaching the calculated value, then cut the slots to depth and then file the nut height down to suit, resulting on a bit less on-guitar work.
Also note that if you are setting the guitar up mainly for side playing, then you'd want higher nut slots to help stop the strings touching the frets when playing near the nut. Raising the bridge/saddles won't raise the string height much at the first few frets.