Things you’ll need:
2) Allen Key. (Size may vary depending on the guitar you are using, so it’ll be good to have a variety. Many acoustic guitars use a 5 mm, Gibson’s usually use a 5/16’s and fenders usually use a 1/8. To be safe, just get a bunch.)
3) Screw Driver
Getting to Know Your Truss Rod
First, The truss rod isn’t exactly meant to fix your action. Although it can help by fixing the curvature in the neck and creating a more comfortable string height, you may want to try adjusting your bridge before you go fooling with your truss rod.
Because the truss is an essential part to your guitar, messing with it can mess up your guitar. permanently.
However with good intention and good judgment this won’t happen.
Lets get down to the basics. Without a truss rod, your neck would bend to the tension of the strings, almost like a bow. And under such tension your neck would either warp or snap rather quickly. so with a truss rod in place this will counteract that force. So naturally loosening your truss rod will create more bend, and tightening it will create a straighter neck. This is vital to know when playing with your your rod (har har har).
You can access your truss rod by unscrewing the plastic (or if your REALLY fancy, metal) plate on the top of your head-stock. On some guitars there wont be a plate on top covering the truss rod. On older guitars (I’ve seen em like this on old Fender strats) the truss rod will be at the bottom of the neck and might require you to remove the pick guard.
Note : if your guitar or bass has duel action truss rods (two truss rods) this guide won’t help you and i recommend going to a professional for this job. (you will see two truss rods on guitars and basses with more then the normal amount of strings i.e. 6+ string basses and 12 string guitars.)
Neck Relief and Curvature
Now before we begin we gotta make sure your neck has the right amount of curvature. this is completely preference really, someone who might want to play slide will need more neck curvature then someone who wants to play metal. what most people do to check neck curvature is look from eye level the head-stock to the bridge, to get an idea of what the neck curvature looks like. However this isn’t very reliable.
One way to measure the amount of relief is to hold down the first and last frets, and to measure the height from the 7th fret. A good/fair amount of height should be around .1 mm to .4 mm.
The second way (the lazy mans way), which is the way I usually do it has basically the same idea as the first way but you measure from the 12th fret., only you don’t measure. instead (while holding down the first and last frets) use the thumb of the hand holding down the last fret and tap the string over the twelfth fret. there should be a relatively small gap between the two. If the string touches the fret then the curvature is too straight. Little something i learned from a YouTube video sometime ago.
Time to Adjust
When turning the truss nut, turn in very small increments. I mean very small.
Too much loosening will cause major warp-age. tightening too much will cause it to snap. And remember, a little bow on your neck is good.
Before turning the bolt, make a mark of where the truss rod is when you start and when you end. make sure your allen wrench is nice and snug against the nut, because stripping the nut obviously won’t lead to good results. i recommend loosening the nut before tightening.
Some people prefer taking off/loosening the strings before adjusting. i prefer to keep them on/tight because you get to see where the strings will lie when adjusted, as where taking them off will make the neck straighter and throw you off. keeping them on will not damage the neck. However, if you’re adjusting your basses truss rod, then i recommend loosening the strings, or if the guitar requires you to loosen them to access the truss, go right ahead.
SLOWLY turn the truss. A little turn will go you a long way trust me. Along the way check the relief and curvature of the neck and keep adjusting till it’s to your liking. never adjust any more then it can adjust.
Adjusting the String Height
Alright. when the curvature is at its prime, replace the headstock plate or the pick guard. Next step is to fix the string action.
If you have a tune-o-matic locking bridge, the adjustment will come from the saddle piece from the two screw on the end. If its a fender style bridge each saddle has two bolts on each saddle which will raise the action individually.
When raising or lowering the action make slow and small increments to the bolts (as usual). Once you think the string is at a reasonable height to your standards, play the string on each fret to make sure there are no dead spots on that string. If you’re getting a lot of fret buzz near the first and last frets, you may want to raise the action, or even loosen the truss rod a tiny bit. If you’re getting a lot of fret buzz towards the middle, you’re neck relief may be a little too much. (Or, if you like the neck curvature as is, just raise the action.)
Make sure all the strings are relatively the same distance from the fret board.
Note: On acoustic guitars, this will be a lot different and will be a lot more difficult to address the problem. You may want a professional to fix this.
Fixing the Intonation
Fixing the intonation means making sure the guitar is in tune with itself and that every fret plays the right note. After playing with your truss rod and string action, I guarantee your intonation will need fixing. This isn’t very vital to the guitar, as it will be vital to you.
Needless to say, i recommend you do it.
Your guitar should now be easier to play and have better tone. Now return to being the marvelous player you are. Have a pudding pop for your troubles.