Setup for Great Action

Step 4: Nut Height

In all honesty, if action is still high at this point, the nut is probably shimmed too high.

Most JEM guitars have the nut shimmed too high from the factory. On a few of my JEMs I removed the nut shim (brass piece under the nut above the wood that can be seen if you look carefully) because the clearance between the open note and fret 1 was too high. Remember the nut only effects the clearance/sound of the open strings but can greatly raise action of the entire fretboard. The nut has to be just high enough to let all the open strings ring without buzzing from touching fret-1. Once you depress fret-2 or higher, the nut height is irrelevant.

Look at the clearance at fret-1 of an open string like the low-E to see how much clearance is there. Watch the low-E note vibrate and see how much clearance remains at fret 1. Now compare this to the fretted F-note... hold fret-1 and let the string ring while visualizing or measuring how much clearance is at fret-2. If the clearance at fret-2 is much less than the first measurement (open string over fret-1) then the nut can be lowered.

Basically the nut can be lowered as far as possible as long as there is no buzz when each open string is let ring. Lower the nut too far and open strings will buzz. If you're not sure about this, I'd hold off and let a competant tech perform the mod. If the truss rod adjustment and bridge height is off then you can screw up the nut height badly. Then again, if you simply remove the shim, you can reinsert it with minimal fuss or put a thinner one in. Ibanez sells three shim sizes and other vendors probably do as well. The shims will fit most locking tremolo nuts.

Sometimes Ibanez will use half shims to compensate for an unlevel nut cut. The idea is to get the nut level so you can use two shims, half shims, etc. to achieve this goal. Half shims are used to raise one side of the fretboard, for example to use under the low-E, A & D strings to get that side of the nut higher. Ken warns us to take caution and pay attention to which side the shim is placed under if a half shim is used. Putting it back on the wrong side would not be helpful in obtaining good action.

If the nut is still too high you need to file the wood at the nut down with a fine grade flat file that is the width of the nut. Use extreme caution, as removing too much wood can ruin the nut cutout and require extra shims. I advise to let a competant tech perform this mod if you are uncertain how to proceed. At minimum, have extra shims handy in case they are needed, and proceed slowly. File the wood under the nut minimally, then recheck. Repeat as necessary.

Summary - Step 4
Quickly assess nut height by looking at the string height at the bridge with an open string compared to the same string depressed at fret-1. If the action is significantly improved when fretting the note, the nut is likely to high. Too high a nut will negatively impact action along the entire fretboard. Too low a nut will cause open notes to buzz on fret-1.