The Perfect Bridge Adjustment
by Daniel Brooks
It is always a good idea to do a set up on any new guitar. Some manufacturers are good about attending to all the details before they ship out one their instruments, and most are reasonably playable right out of the box, but not always. Individual preferences can vary enough that the factory adjustments done just to get the guitar within the normal range of what is commonly acceptable might make your new instrument feel like someone else’s old shoes. A good set up, one where you measure all of the things that can be measured and adjust all of the things that need to be adjusted, is a good way to familiarize yourself with your new guitar and insures that that your instrument is fine tuned for both you and your guitar’s optimum performance.
But what about your old guitar? You know, the one you’ve been playing the longest? You probably tweaked it to perfection years ago, and now you just check it every so often to make sure the neck is still straight and all of the screws are tight. Believe it or not, years of restringing, retuning, travel and playing might be cause for a basic set up. Over the years, the moving parts with which you adjust your string height and intonation can move, ever so slightly. If you haven’t checked it since it was new, a little tweak of your bridge height and intonation might be necessary, especially if you have ever changed your string gauge.
Heavier strings carry more tension. They pull on the neck a little more, maybe even a lot more, than lighter strings, and any change in string gauge from heavier to lighter, or lighter to heavier can create a slight change in the neck’s profile. If your action is set low, this slight change can make your guitar a lot less musical.
Heavier strings also sit a little higher on the bridge. A change from a .046” to a .048” or a .050” lower E string will raise the center of the string’s mass, it will actually sit one or two thousandths of an inch or more away from the bridge saddle it rests upon. This may not sound like much, but combine it with a slightly more bowed neck, and the string actually has to bend a little further to reach the fret. If that bend results in even a two or three Hz change in the note’s frequency, you have an intonation problem. It may not be enough to render your guitar unplayable, but it will be just enough to make it sound just a little off.
Fortunately, a simple bridge adjustment is easy and effective. It is the bare bones of the basic set up. You’ll need a few basic tools, which will vary, depending on what kind of bridge is on your guitar. No matter what kind of guitar it is, you’ll need a feeler gauge or a good ruler marked in 1/32" and 1/64" (0.5 mm) increments to measure your string height above the fret, a good chromatic tuner, and a towel or a cloth to protect your guitar’s finish from tool marks.
The first thing to do is restring your guitar and tune it. Recheck your tuning whenever you adjust anything during the set up. If you have a Strat, you will need a set of Allen wrenches, a #1 and a #2 Phillips screwdriver. Adjust the tremolo, if you have one. If it sits high, at an angle, open the back plate and tighten the two screws that attach the spring claw to the body until the tremolo sits parallel to the body. Turn both screws an equal number of turns so the tension is equally distributed.
Now it is time to adjust your action, or string height. Tune your guitar and then measure the space between the 17th fret and the bottom of each string. Fender recommends a minimum string height of 4/64” (1.6 mm) above the 17th fret. Gibson recommends a minimum of 3/64” (1.16 mm) between the high E and the 15th fret, and 5/64 (1.98 mm) between the low E and the 15th fret. This can vary quite a bit depending on your preference but typically, if you play with a light touch you’ll probably find a lower action is preferable. More heavy-handed guitarists and slide players will probably want to raise the action a bit to avoid fret noise.
Each bridge saddle on any model Stratocaster will have two Allen screws that set the height of each individual string. Find the correct Allen wrench and turn both Allen screws in each bridge saddle the same number of turns. If you are trying to raise your action, a clockwise turn will put more of the screw between the saddle and the bridge plate effectively raising the saddle and the string that rests upon it, and a counterclockwise turn will lower it. Be sure to turn each Allen screw only a quarter turn at a time, and always give both screws for each saddle the same number of turns. You want to keep the bridge saddle parallel to the bridge plate. It will negatively affect the sound and performance of your guitar if it is not parallel. When you think it’s where it needs to be, retune the string and measure the action. Play each note on each fret on that string. If it buzzes or plays the same note as the next fret, you have dropped your action too low.
There are a couple of different bridge designs used on a Telecaster. One of them works exactly like that of a Strat, with individual saddles whose height is adjusted by a pair of Allen screws. You can adjust it the same way. The other has three “barrels,” each of which works as the bridge saddle for two adjacent strings. At each end of each barrel is a screw that goes though the barrel and rests on the bridge plate. A clockwise turn of each standard, slotted screw will put more of the screw between its end of the saddle and the bridge plate, raising just that string. Here the bridge saddles do not have to be parallel. Each string must be adjusted for its own optimal height. It may sound a little wacky, but many believe this design contributes to that characteristic sound of a Tele, so they keep making them that way.
You cannot adjust the height of each individual bridge saddle on a Les Paul, or any guitar with a Tune-O-Matic bridge. You can only adjust the height of each end of the bridge itself. At either end of the bridge is a wheel used for this adjustment. Unlike other bridge adjustments, each clockwise turn sinks a little more of the stud, upon which rests the bridge, into the bushing, which lowers the action. Fortunately, the bridge saddles are each height-adjusted for the fretboard radius.
Now that the bridge is adjusted for perfect string height, we are ready for the last step in the set up. To do this adjustment on a Stratocaster or a Telecaster, you’ll need a #1 Phillips screwdriver. On a Les Paul or any other guitar with a Tune-O-Matic Bridge you’ll need a #0 or #1 flathead screwdriver. The adjustment itself is universal, the same rule applies to every kind of guitar or bridge.
When the intonation is perfectly adjusted, the 12th fret should mark the exact halfway point on the string between the nut and the bridge. When the fretted string is exactly one half the length of the tuned, open string, it vibrates with exactly twice the frequency of the open string, an octave. Of course, the diameter and the height of each string will affect this ratio, so we have to adjust the length of each string.
Tune your guitar. Play a harmonic at the 12th fret of any string. Touch the string above the 12th fret, lightly, without fretting it, and pluck it with your other hand. It should make the pure, beautiful bell-like tone of the two halves of the string harmonizing with one another. Fret that same string at the 12th fret and pluck it again, it should make the exact same note. If the fretted note is a higher pitch than the harmonic, then the distance between the bridge and the 12th fret is shorter than the distance between the bridge and the halfway point of the open string. Lengthen the string. Turn the screw at the far end of the bridge clockwise a whole turn. Retune the string (check all the strings) and repeat until the harmonic and the fretted note are exactly the same pitch then adjust the next string.
Now, plug it in and play. Isn’t that better?