This article was originally featured on doughnutmag.com and has been used with permission.
The Tune-o-matic bridge (what a great 50s name) is common on Gibson and Epiphone guitars, especially shapes such as the Les Paul and SG, usually with a pretty solid stopbar sitting just behind it.
To Adjust the guitar bridge, all you need is a flat head screwdriver and an accurate measuring tool. A metal ruler with millimeter markings is ideal.
Tune your guitar to standard tuning and place the the ruler on the twelfth fret, keeping it neatly above the fret itself, not the fretboard. Measure around the third and fifth to get an idea of the overall height.
Adjusting The Truss Rod
Before lowering the bridge, you may want to adjust the truss rod slightly. This can done quite easily with a hex key, but is something that most people feel uncomfortable doing themselves.
Quarter turns are all you need to help shape the flex of the neck. Clockwise will tighten the truss rod (pull the headstock back), anti-clockwise will loosen the truss rod and allow the neck to slope forwards. We’ll save adjusting the saddle and intonation for another day…
Adjusting The Tune-o-matic Bridge
If you’ve got your truss road to where you need it then it’s time to lower that action. You could use the rings on the bottom of the Tuno-o-matic style bridge, but a screwdriver is easier and is recommended for precision.
Clockwise to lower action, anti-clockwise to raise it. Start with high string (the far nut). Measure your action, adjust, play and re-tune a few times until you are in the 2mm area and happy that there isn’t too much fret buzz. The repeat on the low string (the closer nut if you’re in the playing position).
“Vital to get the neck right first. A slight curve is desired if you want to get the action low and not have it buzz. Put a capo at the first fret (like for an F) and then hold a string after the last fret. You should be able to push the string down in the middle a distance somewhere between a credit card and a business card. If there’s no gap, loosen the truss rod. If there is too big a gap then tighten. Once this is right you can tweak the bridge height.” – geektard