#1
....to adjust the intonation from the tune-o-metic bridge on my '61 reissue SG? All the advice I get is that if the 12th fret harmonic is lower or higher than the 12 fret to adjust it accordingly. Sometimes the problem is that the 12th fret is out of tune from the harmonic. The G string on my guitar has both the harmonic and fret out of tune (flat) but I can't push the intonation bar at the tune-o-metic bridge any further back.

Let's say you guys tell me to go ahead and adjust the truss rod because it's needed:

At that point, should the fretted 12th G string match with the open string AND then when that's settled get the harmonic to match the corresponding 12th fret of the string I'm doing? My Low E has the 12th fretted note as sharp but the harmonic as a hair flat but in tune while my G string has the fretted and harmonic flat. If I turn the truss rod one way isn't it going to mess both of them out? Or is there like an equilibrium where there's a sweet spot where things will just settle as long as I find the right spot?


Thank you ahead of time, I just get really nervous doing this stuff. Happy Holidays!
#2
Seems you have it the wrong way around. If the 12th fret and harmonic are flat, you should adjust the saddle closer to the neck, not back or away from it.
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#3
The first thing I do (and while working as a guitar tech for several years) is to get the neck profile to look right, using the truss rod and/or shims if necessary (assuming the frets are already dressed well enough). That will influence how much added tension is imparted to the strings when making them contact the frets, and will therefore influence the intonation as a result. After that is all settled I adjust the intonation as the final adjustment.
#4
Uh, how about doing a bit more research on how this all works.

A quick read is the new owners manual from ESP support site. I know you have a Gibson but give it a read. It's concise.

I always setup the neck relief first.
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#5
... and yes, if the fretted note is flat you need to move the saddle closer to the neck to shorten the string length.

Be gentle with an old truss rod. As a precaution I always place the neck across my knees and press against the back of it between them while I adjust the nut. It lessens the tension and permits the torque to be more likely to turn the adjustment nut than to twist the rod itself and/or stress the anchor within the neck.

As for the saddles, there is no risk and no need to be nervous.
#6
Quote by metalmingee
Uh, how about doing a bit more research on how this all works.

A quick read is the new owners manual from ESP support site. I know you have a Gibson but give it a read. It's concise.

I always setup the neck relief first.


Neck relief is the very last thing you should be setting up, after everything else is correctly rigged.
#8
@dspellman If things are more or less close to where they should be then I agree that truss adjustment can be done afterward, or independently. High action that results from too much relief will throw intonation off and in those cases the relief needs to be brought closer to a final adjustment in order for the intonation adjustment to be right as the final setup.

In general, for the final set up these adjustments may need to be re-iterated if things are very far off to start. I have always started with ensuring proper neck relief first, then going for intonation and it worked for my customers (and for me).