Okay---frets are leveled, crowned, and polished well. Thanks to Uncle Mike for filling in on polishing. We might have overlooked dressing the fret ends to soften the sharpness of the filed bevel. Now on to the setup of nut and saddle. After the nut is seated properly (both against the fingerboard AND the neck, I use the 'half-pencil' method of marking how deep the slots should be cut. Above that line I approximate half the diameter of the strings to determine where to cut and/or file the top of the nut. The intent is to separate the strings with just enough of a slot to keep the strings in place. Ideally, the slots should be rounded troughs the same or greater diameters than the strings they cradle. If too tight, they will pinch the strings and cause problems in tuning. Mark the outermost strings slightly more than 1/8 inch in from the fretboard edge and divide the spaces accordingly. The slots should descend downward toward the head to provide a definite point of contact at front edge. Round and shape the top of the nut blank to your preference. Now with the metal straightedge sitting on the bottom of the slot, raise the bridge end and insert a spacer of 3/32"(+/-) and see how much the saddle needs to protrude above the bridge. Mark/cut/shape to that line. Relieve the back end so the string has a nice, soft corner climb. For a truer sounding instrument refer to the past issue on intonation entitled Location, Location, Location.
NOW you're ready to string up. You now have an instrument that at least will play well. Re-insert your spacer under the strings at the 12th fret and adjust. If anything, you might discover that the strings still need to come down where the saddle is. That's because the neck is bowing up from the
string tension. This amount always varies according to the natural stiffness of the neck material, thickness, etc. Often, it is just the right height. Now play. If you have buzzing, you may not have dressed frets well enough. Don't despair---frets always were and always will be the hardest
part of the setup.