When you have your guitar strung up and tuned, you need to check the curvature of the neck. You may see on other websites that a gap of 1/64” (0.4mm) - 1/32” (0.8mm) is required…so what does that look like, especially if you don’t have an engineers rule or other measuring device? A standard credit card is about 0.65mm and standard business card is about 0.3mm. You can probably find these two things in your wallet or purse. Get them out and have them handy.
Pick up your guitar and hold it in the playing position. Put a capo or small clamp on the first fret (closest to the nut) to hold the string down. The string needs to be contacting the first metal fret. You can also have a friend hold down the low E string. Next, with your picking hand, hold down the low E string at the 17th fret. As you should see, the string forms a straight edge between the first and 17th frets.
There should be a slight gap between the E string and the 9th fret. If not, your neck has “back bow”, which we’ll address later. Still holding the string down, use your free hand and try to slide the business card under the E string right on top of the 9th fret. If it slides under the string without contact, try the credit card. If the credit card slides in without contact, try the two cards together. If this doesn’t make contact, your neck needs some work! Ideally, the business card should clear the string, but the credit card shouldn’t. If the credit card clears the fret and string with ease, we have some “bow”, or relief in the neck.
On most guitars, the same rule for truss rods holds true: Right is tight, left is loose. Looking at the truss rod adjustment on top of the neck near the tuners, the right/left arrangement is from the top of the neck looking toward the body of the guitar. If you have back bow, you need to loosen the truss rod, or turn the nut on the truss rod left. If you have bow, you need to tighten the truss rod, or turn the nut on the truss rod to the right.
As a technique, I always loosen the truss rod before I do any adjustment. If you start cranking the truss rod down, and it is already pretty tight, you may break it, and this is something you won't be able to fix at home in an afternoon. If you feel the least bit uncomfortable at this point, take your guitar to a repairperson/luthier.
There are generally two types of adjusters on truss rods: A nut for Gibson style truss rods, and a hex-head screw for just about everything else. The hex-head is most common on imported guitars. Make sure the hex-head driver that came with your guitar is well seated – you don’t want to strip it out, or again your have trouble on your hands. Generally about a ¼ turn is enough to move the neck. If you move it more than a full turn, you may have an issue.
Step Three: Check string height at the nut. A lot of the nut-work on import guitars leaves something to be desired. To check the height of the nut, start at the low E string, and fret it on the third fret (a “G” note). The string should be sitting on the first fret, or just above it. When I say “just above”, I mean close enough just to see some light through the gap between the string and the fret. Try holding the string down on the third fret and "tap" the string above the first fret, kind of like checking the neck relief. You should be able to press the string down just ever so slightly onto the first fret.
Try this procedure for all of the strings. If there is a big gap, your nut needs some work. Can you fix this? You can if you have some nut files. If you don’t you may need a repairperson to take a look at it for you. The height at the nut is critical to a good playing guitar. If it is too high, the string will be too low at the 12th fret, probably causing a nasty buzz and intonation problems.
Before you continue, take a look at your bridge -- we're heading there next. If you look at both bridges pictured below, you can see that the saddles on both are arranged similarly, with an adjustable saddle for each string.
Gibson-style Bridge
This bridge has six individually-adjustable saddles which are adjusted using the screws you can see at the bottom of the bridge facing the stop tailpiece. The screws have a slot head, requiring a flat-head screwdriver. On some guitars these screws face the other way (usually on the older or replica models).
If you have to adjust a saddle, place a soft cloth below where you're going to insert the tip of the screwdriver. This will help you avoid gouging the top of your guitar if you slip. Turn the screw clockwise to move the saddle back and counterclockwise to move it forward. Make small turns because a little turn can make a lot of difference. After every adjustment to the position of the saddle, retune the string to pitch and compare the 12th fret note and the open string. Repeat the operation until the string has the correct intonation, then move on to the next string.
Fender-style Bridge
Although the Fender bridge looks different, the principles of setting the intonation are exactly the same as a Gibson bridge. You move the saddles with an adjustment screw (in this case, a Phillips head screw) until the note at the 12th fret and the open string are the same.
Note: If these saddles are in a straight line, the guitar is probably not set up properly!
Step Four: Set the approximate positions of the string saddles on the bridge.
First, determine the scale of your guitar. Measure from the body-side of the nut to precisely over the 12th Fret. If you double this measurement, you have the scale of your guitar.
Using the distance from the nut to the 12th fret (we’ll call this measurement “x”), measure from the 12th fret to the bridge. Using the screws on the back of the saddle, set the individual saddles to the following specs:
Note: I find it is easier to make the initial adjustments with the strings loosened. Once you set the saddles, tune the guitar back to pitch.
Low E:
1/8” or 3.2mm longer than X
A:
1/16” or 1.6mm longer than X
D:
1/32” or0.8mm longer than X
G:
1/8” or 3.2mm longer than X
B:
1/16” or 1.6mm longer than X
High E:
1/32” or 0.8mm longer than X
We get the final settings once we get our saddle height, but this will get us close.
Step Five: Set string height at saddles.
Measure at the twelfth fret and set saddles so the height between the bottom of the low E string and the top of the twelfth fret is about 1/16" or 1.6mm. The High E should set just at 1/16” or 1.6mm, this is about two credit card widths above the 12th fret (we know you have at least two credit cards!). The other strings should be the same height, following the radius of the fretboard. This is easy with the Gibson bridge -- just crank it up and down, and the shape of the bridge conforms to the fingerboard in most cases. The Fender-style bridge has more adjustment range, and it may take a little more time to set it up.
Remember – This is a starting point to get your saddles set. Your playing style may make you either raise or lower the saddles. We’re just trying to get in the ballpark.
When you complete this, the saddles on your bridge should be somewhere in the middle of their adjustment range. If they are sitting flush on the body, or maxed out, your neck angle needs to be adjusted, and it may be best to get a qualified repairperson to complete this job for you.
Step Six: Fine tune the intonation setting with a tuner.
What we are going to do here is actually adjust the length of each string. This is the only way to make sure your guitar will play in tune all the way up the neck. You’ll need an electronic tuner for this job. You’ll need some small screwdrivers --flat tip or Phillips, depending on your bridge.
Follow these steps:
1. Hold the guitar in the playing position.
2. Hook up the electronic tuner and put it in a position where you can see it clearly.
3. Tune the entire guitar. Make sure you take your time and get it as precise as possible.
4. Start with the low E string. Play the string with a pick, and make sure it is in tune. Next, fret the string at the 12th fret, play the string, and check the tuning. It should show an E in tune.
5. If the note played at the 12th Fret is in tune like the open string, the string is properly intonated. If is isn’t continue to step 6.
6. If the note played at the 12th Fret is flat (below E), take your screwdriver and move the saddle toward the pickups. If the note was sharp (Above E), move the saddle away from the pickups. The General Rule: Flat = Forward
7. Continue this process until the open string and that same string fretted at the 12th fret are in perfect tune with each other.
8. Continue this process for all strings, and keep going back and checking the settings for each one.
