I don't know what it is about a truss rod that can make grown men cower like little boys at the thought of having to make an adjustment. This should help break your fear and allow you to wear pants again proudly. Much of this fear comes from techs that will tell you "you can ruin your neck if you mess with the truss rod!", which, is a really good way to scare you into relying on the tech to do all your light work for you. Can you ruin a neck adjusting the truss rod? Sure, if you're an IDIOT! So, if you're an idiot and can't follow simple instructions, STOP HERE, and keep paying that local tech whatever he wants to keep your guitar adjusted. Just make sure he ties your shoelaces before you leave so you don't trip and fall and skin your knees since you probably forgot to put your pants on. The rest of you please read on, this is simple stuff, the only requirement is the ability to turn a wrench and the slightest bit of common sense. Overwritten by a blow hard as usual.
Please read to the end and the DISCLAIMER before beginning or making any adjustments, and I cannot stress how important it is to use the correct tool, a good tool, and to have that tool *fully* seated either around the full length of the nut or full depth of the channel. The easiest way to strip these parts is to use a poor fitting tool, or only partially insert the tool on the nut or head to be adjusted.
There are a few types of truss rods, but essentially the truss rod consists of a nut on a threaded shaft [rod] that is pinned in the neck at the other end. It is there to counteract the pressure the strings exert pulling on the neck, by pulling the wood in the opposite direction. This allows you to control the amount of relief you desire in the neck.
Relief is the amount of bow the neck has. Relief allows for the the following fret to be a hair lower than the previous fret so that the previous fretted note has a little extra clearance when played, thus reducing the buzz of the string pinging off the following frets. The amount of relief is a personal issue and some people actually prefer a dead straight neck, while others will prefer ample relief. The lower the action is set the less relief the setup will allow, the higher the action is set the more relief a setup will allow, but the higher the action the less relief is needed for fret clearance as the high action reduces the buzz on it's own. If you fret the first and last fret on the wound E string you will be able to see how much relief the neck has by checking the clearance from the top of a fret [I use the 9th as it's pretty much dead center of the neck] to the bottom of the string. The measurement of this gap is the relief, ie. .3mm of relief at the 9th would be .3mm of clearance between the top of the 9th fret and the bottom of the E string. I've written basic guidelines for what is fairly normal for relief in any give setup on my Action page, but you and you alone will determine what is best for your and the way you play, and the only way to know that is simply, experiment. Straight neck, lots of relief, feel the difference as the string clearance grows through the center of the neck and hear the difference. Adding relief will add action height so you will have to readjust the action to compensate, just the same as straightening a neck will reduce the action height and you will have to raise the action to compensate. Experimenting with all combinations of relief and action will allow you to find the setup that works right for you, and to mentally note what it is, allowing you to keep that setup as you prefer it.
A neck will continue to adjust after the adjustment has been made, for up to 24 hours. Wood can react to stress slowly or quickly, so you should be aware that a second relief check should be made several to many hours later. Slight relief changes should not show later change but large relief changes like the experiments I'm going to have you do next quite possibly will. As long as you're aware, you're educated and the adjustment is, again, simple.
Pictures - eh, coming. Just to illustrate the different Ibanez truss rods and tools. 7mm [RG/JEM] and 8mm [RBM/AR] typical nut on threaded shaft, but they also use an Allen wrench adjusted Allen head shaft that threads into a fixed nut on the other end. These will be either 4mm [JS1] or 5mm [JS1000]. They all adjust the same, the only difference is the tool.
No 2 necks will adjust the same [not true considering there's probably a billion necks out there, but for the purpose of this page lets consider that a truth]. Some necks will adjust a lot to just a small tweak of the truss rod while some will require much more to get the same result. Until you know which you have it's always best to make smaller adjustments. I firmly believe that everybody should get their truss rod wrench out, pull the truss cover off if it has one, and adjust away just to observe the principle discussed here. Start by checking the relief that is in the neck, and then completely loosen [looking at the nut from the tip of the headstock back toward the body - lefty loosey] the truss rod until it's loose. Check the relief again [I would tell you to "sight the neck" also as another way to observe, but that's another page of typing] and you will see how much it moved [bowed]. Note this. Some necks will be in HUGE relief when loose, some will give barely any relief at all which will limit your setup options. Unfortunately there are also just bad necks that will be in backbow with a loose truss rod that will need to have professional attention to train into relief. What does your neck have? The gauge strings you have on your guitar will also affect the amount of relief as heavier gauges exert much more tension on the neck pulling it further into relief. With the truss nut [or rod] loose I usually recommend continuing until it's far enough out to get some grease under the nut so that it will operate smoothly. This can be done at any time and need not interfere with experimenting with the truss rod now.
Let go the other way. As you tighten the nut [looking at the nut from the tip of the headstock back toward the body - righty tighty] it removes the relief in the neck, straightening the neck, and eventually putting the neck into negative relief or backbow. This is where you can really check how much of a turn makes how much difference. Because of the nature of the truss channel and the way the strings are on either side [and on a 7 string you have a string running right in the middle of the truss channel] the amount you can turn the nut is limited to somewhere between 1/8 - 1/4 of a turn, and until you get the hang of how much it changes the neck relief this is about all you want to turn it anyway. Adjust, then check the relief to observe what happened, then play it and see how it feels, at the nut, the lower registers, the middle registers, etc. Repeat and continue adjusting and testing. I want you to take the neck into backbow so you can see for yourself, the sky didn't fall, the neck didn't break, it can be corrected just as easy as, turning a wrench. Once it's in backbow there is no need to tighten further, a guitar in backbow is a guitar that needs a truss rod adjustment. Go ahead and play it, especially fretting the first fret to observe the buzzing, if it allows first fret notes and not second or third to ring out. This is only so that you can see and become familiar with making this adjustment and getting over any fear of it.
Now that you've adjusted the truss rod in both directions you can adjust it back to the starting point or wherever you found that you liked it set through experimentation. That the whole point of this is to not only get over any apprehension and fear of the truss rod itself, but to find that setup that you like the best. On most necks a very small 1/16th turn adjustment can make the difference of .1mm in neck relief and eventually you will get to know your neck and how much is enough. Remember that adjusting the truss rod also means adjusting the action, which is why a lot of this is covered on the Action page as these adjustments go hand in hand. Relief adjustments affect action height, plain and simple.
Unfortunately I'm not going to cover neck profiles here and there are plenty of guitars in all stages of "stored neck disease". This is usually caused [but not always] by a guitar that is allowed to sit unadjusted for years. As the wood continues to shrink it in effect loosens the truss rod. The wood takes this as memory and will show relief in the middle of the neck that will not truss out, in fact the guitar will start going into backbow at the nut before you'll get the mid neck relief out. These guitars will want to stay in whatever the smallest amount of relief is possible to live with the least amount of backbow in the first few frets. There's also a condition called "scarf-joint-itis" where the plane of the headstock piece scarfed into the neck is shrinking counter to the plane of the solid neck, pulling the neck into backbow at the first or first few frets. Another condition where the amount of backbow will control the amount of relief or straightness possible. These are conditions of less than desirable necks but often perfectly serviceable necks, they just won't be useful to those that like very low action or very straight necks.
DISCLAIMER - if it is extremely difficult to turn your truss rod there might be an existing issue with your neck. It could have been factory built with far too much relief at rest, or it could have an unknown condition. I would recommend fully loosening the truss nut as shown above, back the nut [or rod] far enough out so that you can get some grease between the nut and the block, then see if that has fixed the problem. Dry contact between nut and block will also cause creaks when turning making amateurs think there is something wrong. If it is still difficult to tighten the truss rod after lubrication STOP, and let a professional or a friend that is familiar with adjusting truss rods have a look at it for you. Is IS possible to damage a neck adjusting the truss but it is usually in this situation where there is already an issue. You can also damage a neck by continuing to put a neck into more and more backbow until the stress cracks the neck or damages the rod/nut, but, that would be idiotic, so lets just not go there ;)
There are situations where you will want to relieve the
string tension before making adjustments. If there is any play between the nut
[or Allen] and tool from past adjustments made with the wrong [SAE] tool,
partially fitting the tool on the head, inferior parts, or inferior wrenches
with poor fit or wear, obviously any adjustment should be made with no/little
stress on the neck in hopes of preserving the fit and adjustability you have
left in the parts. I cannot stress enough to always use the correct tool, and a
quality tool to do the job.