Every now and then, friends come over with complaints about their guitar: the tone is wrong, the playability is off, tuning stability issues and sometimes even cosmetic issues are brought to my attention. I’m happy to address all issues, but some issues are so easy to solve that I think it’s wise to write this article. I’m talking, in particular, about the action of your (electric) guitar. Acoustic guitars can also be adjusted but that’s a rather tricky job compared with electric guitars since the bridge is glued to the top on acoustics versus mounted on movable studs on an electric. Hence I’ll be focusing on electric guitars in general.
To adjust the action you need a few basic tools, time and common sense. A tool fitting for the height adjustment of your bridge is the first piece of gear you’ll be needing. On tune-o-matic bridges that’s often a flat screwdriver, on 6 point vintage tremolo’s, found on strats, a philips screwdriver is needed, but many other guitars use allen wrenches for the adjustment (think of Floyd Roses, Kahlers, Wilkinsons, Hipshot tremolo’s, and many like that). Just look at the way the bridge is mounted and often it will show itself. You’ll also be needing some small gauges though that’s optional. I don’t use them myself but many techs and players like to use them. Why they might come in handy will be explained later. And finally, a key or allen wrench to adjust the trussrod. Some also use a capo, but I’ve never used that method; the following way works fine for me.
Your action can be off at three points on the neck of the guitar: near the nut, around the 12th fret and near the end of the fretboard. For each of those, there’s a solution. I”m assuming the nut has been cut well, because if you have to deepen the slots of the nut or maybe even raise the nut or, as a worst case scenario, replace the nut all together, it’s a more complicated job than just adjusting the action. It’s not a horrible job to do, just allow yourself some time to recut the nut and be sure to have a lot of blanks to cut, because you’re guaranteed to mess some blanks up! But… that’s a whole different story and should be saved for another time.
If the action is high at the nut or from the nut towards the 12th fret, but goes lower gradually towards the bridge, you can do either of three things. Leave it that way and accept the issue (assuming the action isn’t so low near the end of the fretboard that the string buzzzes). Lower the nut or the slots in the nut (see previous paragraph about the nut!) or tighten the trussrod a bit. In a previous article I discussed the reasoning behind the trussrod, so I won’t go too deep into that subject. Sufficife to say, the trussrod acts as a counterbalance to the pull of the strings. Since the neck is made of wood it will bend when almost 70 kilo’s of tension is put on it via the string tension! The trussrod negates that issue. Conversely, if the strings pull too hard for the trussrod to cope, the wood will bend even more (aka: headstock goes ‘up’, creating a curved neck). So if that’s the case, simply tighten the trussrod! Do not start tweaking the bridge because that is pointless. The bridge will have a huge effect on the string near the end of the fretboard but not so much near the nut, so just leave that alone.
The trussrod is often hidden behind a cover or at the heel of the neck which is obscured by the body, adding to the almost mythical properties of it. I’ve heard horrorstories of trussrods being tightened so intense that the trussrod broke through the neck or even worse, broke the trussrod itself! Thankfully, that happens very very rarely and if it happens it’s often because the guitar itself was already in bad shape. The nut of the trussrod can rotate smoothly so if you simply can’t go any further (clockwise or anti clockwise, doesn’t matter!) you know you’ve hit the end of the range of the trussrod, so leave it there. If you feel you want even more effect of the trussrod, it might be prudent to go to a qualified luthier and have him examin the guitar because there might be something more structurally wrong with the guitar than just a trussrod going out of reach. Remember, the trussrod is there as an aid and as part of the stability, it’s not a miracle worker.
If the action is low at the middle of the guitar, causing the string to buzz out, you might have a chance of sorting that out with the action, too. It can be that the trussrod is so tight that the headstock is going ‘down’, causing a severe backbow. Combined with a nut that’s too high you get a bump of the fretboard in the middle and high action at the nut. Since many people try to raise the action by raising the bridge, the perfect recipe has been created for bad playability. Simply give the trussrod a bit of slack, lower the bridge and when it comes to high action at the nut, see my previous statement.
High or low action at the higher frets, that’s where the bridge is the perfect remedy! Now you can simply raise or lower the bridge to adjust the action right there. Now you do need the screw driver where you just needed the key to the trussrod in the previous two cases.
There’s an issue that might require some bigger tweaks: a wrong neck angle. If the neck angle is too shallow, your bridge might not be able to go deep enough to get a playable action. If the neck angle is too steep, the bridge will have to be set up quite high to get it playable. The latter just looks strange (and on some guitars, the bridge studs might warp under the pressure of the strings), but still: that problem is not as big as the first. A remedy for the latter issue can be a neck reset (and in the case of a bolt on neck, a reshaping of the neck pocket). In the first case, though, the remedy is quite simple: shimming. You get a piece of wood veneer or if it has to be thinner, a piece of paper folded over 2 or 3 times. Push it in the neck pocket towards the back, screw the neck back on and now the neck is higher than before. Assuming the bridge hasn’t moved, your action is now a lot lower! This is only if the bridge just can’t go any lower without huge mods. Shimming can, of course, only be done on bolt on necks.
Many issues can be solved easily on a guitar as long as you keep your head cool and think each step through. For adjustment on the trussrod, again, see my previous article. Just be careful but don’t treat it like the Queen’s Crown Jewels! If history is any indication, it can take quite a beating; so many guitars from the 40s and 50s that had trussrods still work just fine, as a silent statement regarding the strong yet almost invisible force of the trussrod.