Matt said:
ok, I'm going to sound very silly here, but what exactly does the nut do? I've never understood! can anyone explain?
regards
Matt
Matt, not to contradict Marnold here, because he was partly right, but the nut's main purpose is to set the scale length of the instrument in conjunction with the bridge.
Have you ever noticed that strats and teles usually are listed as having a 25.5" scale length, while Les Paul's are listed as having a 24.75" scale length? That number is the distance, in inches, between the guitar's nut and bridge. The same goes for bass guitars, usually found in either 34" or 35" scale lengths, although ocassionally found in short (30") scale as well. Newbie bass players will find the 34" scale length to be much more comfortable than the 35".
The scale length determines the distance between individual frets, so, the distance between the nut and the fifth fret will be greater on a tele or strat than it is on a Les Paul or SG. As the scale length increases, so does string tension as well, so all other things being equal, it's easier to bend note on a guitar with a shorter scale length. With less tension, the string bends easier.
The strings must be able to move over the nut freely without binding. You can tell if your strings are binding when you get that sort of "ping" as you tune up to pitch. That is an indication that the string slots in the nut need to be relieved. This binding can be a real problem on a tremolo-equipped guitar, as the instrument won't return to pitch properly when the wang bar is used. This was one of the reasons behind Floyd Rose's development of his tremolo system. As Marnold pointed out, it "locks" the string in place at the nut, so there is no movement there.
The second purpose for the nut, on both standard
and Floyd Rose style guitars (sorry Marnold) is to set the string height in relation to the fretboard. If you look up setup specs for guitars, you will usually see a string height specification at the first fret. This is set through the depth of the slot in the nut. If you go to a lighter set of strings, this spec can change, causing string buzz, because the nut is cut too deeply for the lighter gauge strings. Proper string height has to be maintained, whether using a standard or Floyd Rose locking type nut.