I have a reletively new guitar that has the following issues, even after intonating by adjusting the bridge saddles:

1. When cording the lower frets, I tend to get sharp notes, espcially on the low E and the G strings.
2. The G string goes out of tune very easily with simple string bending or light use of vibrotto.

From what I have researched, these two issue are most likely due to the nut not being set up properly. Problem is, I don't even know how to tell if a nut is badly cut. Is my only option to try and find a guitar tech to inspect and adjust the nut if necessary? If so, what kind of cost could I expect?

the g string probably goes out of tune because of a bad tuner, not the nut.

what kind of guitar do you have, amd does it have a trem? a picture of the nut might help too
Ibanez S7521qm 7 string
Ibanez S771pb
Fender Jaguar HH Special
PRS SE Custom 24 7 string
Epiphone Les Paul Custom
You can check the nut yourself.

First make sure that your truss rod is adjusted to where you feel comfortable playing the guitar and there is minimal or no buzz in the middle of the neck. If you attempt to cut the slot lower with too much relief you could end up having to toss the nut because you cut it too low and when adjusted back to a standard amount of relief an open string buzzes when plucked.

Once that is done also check the first few frets for wear. If there are any deep groves in the frets this could also cause poor intonation.

Make sure that your bridge action is also set to where you feel comfortable playing the guitar. Keep in mind that lowering the nut slots will also lower the action so you may have to adjust the bridge higher after modifying the nut.

Once this is done press each of the strings one at a time at the third fret. Sight the distance between the top of the first fret and the bottom of the string. There should be a tiny (as in a few thousandths of an inch) of room between the two. Typically strings that play sharp at the first few frets are set too high at the nut. You have to press the string further down causing the string length to become too short and producing a slightly sharp note.

What you can do if it is quite high at the nut is take a file that is the same width (or a couple thousandths wider) as the gauge of your string and slowly lower the nut slot. Check and re-check your work as there is no saving the nut if you have gone too low (well almost no saving it unless your good with glue). When you are using the file make sure to file at an angle similar to that of your head stock (on a Gibson or similar guitar. If it's a fender you might have to estimate the string angle necessary).

You should be able to hear the difference this makes as you file the slot lower.

As far as the G string is concerned it could be sliding up the side of the nut slot as you bend or use vibrato. You can check this by playing a bent note on the string. If it stays sharp press on the G string behind the nut to re-seat it in the slot. Once the string is reset in the slot check the note again and see if it's back in tune. If the note is back in tune than the shape of the nut slot is either too wide and/or too high for the string. To remedy this you could shave down the top of the nut so that the string sits at it's diameter at the top of the nut. You could also try polishing the nut to see if the string is just binding in it, you should also polish the nut after filing. There could be a problem at the bridge or the tuner as rtfk101 suggested as well.

Keep in mind that you could also have a twist in the neck whereas the treble strings have more relief than the bass strings. If this is the case you could attempt the above but you may never get perfect intonation.
Last edited by spicyfourpiece at Dec 3, 2014,
Thank you spicyfourpiece. I will check those things to try and diagnose the problem but I'm not sure I am anywhere close to qualified to start filing the nut. Like you said, you can't go back.

The actual guitar is a Gretsch 5120T.
Take it to a good guitar tech. Getting a nut reworked shouldn't be too expensive and doing it yourself without the knowledge of how to do it can get you into more trouble. If you don't have the know how take it to someone who does. Check around with local players and find out who they trust to do a good job, they might also be able to tell you how much it will cost. It's not hard to do, but you have to know how...

Both E and G strings going out can be the same problem, nut slots too high. It wouldn't be the first time I've seen that on factory guitars. Quite often they aren't set up great and need to be fine tuned before they play right.

String going out of tune by bending it or vibrato could be a flaky tuner, or tuning method, or stringing method. Always tune up to the note you want, never tune down and leave it there. That lets the string stretch and go flat easily.

When stringing, I cut the string about 1 3/4 inch longer than the tuning post and that lets it get around 1 1/2 to 2 wraps, that's plenty. More than that can let it stretch for quite a while before it settles into place, and cause tuning problems. Make sure and hold good tension on the strings when bringing new ones up to pitch then give them a good stretching.
Hmmm...I wonder what this button does...
Quote by columbiar
Thank you spicyfourpiece. I will check those things to try and diagnose the problem but I'm not sure I am anywhere close to qualified to start filing the nut. Like you said, you can't go back.

The actual guitar is a Gretsch 5120T.