If you are a beginner guitarist or have never studied guitar construction, the fact that the fretboard on an electric guitar is not flat may be a shock. All electric guitar fretboard's have a slight radius to them. The reason for putting a radius on the fretboard is to make the guitar more comfortable to play. Every guitar manufacturer has slightly different radii on their guitars. Here is a list of guitars with their standard fretboard radii.
|Modern Fender Stratocaster American guitar||9.5" (241 mm)|
|Vintage Fender Stratocaster guitar||7.25" (184.1 mm)|
|Gibson Les Paul guitar||12" (305 mm)|
|Gibson Sg guitar||12" (305 mm)|
|Ibanez guitars||12" (305 mm)|
|Jackson guitars||16" (406 mm) or compound, from 12" (nut) to 16" (heel). A compound radius is common on their newer models|
|Warmoth guitars Compound||from 10" (nut) to 16" (heel)|
|PRS Guitars Regular||10" (254 mm)|
|PRS Guitars Wide Fat and Wide Thin||11 11/16" (42.8 mm)|
|PRS Guitars 513||11 43/64" (42.4 mm)|
|PRS Guitars Hiland||11 21/32" (42 mm)|
|PRS Guitars Santana||11 1/2" (292 mm)|
|PRS Guitars Custom 22/12||11 1/2" (292 mm)|
|Most electric guitars with LSR roller nuts||9.5" to 10" (241 mm to 254 mm)|
|Most electric guitars with Floyd Rose bridge||10" (254 mm)|
|Traditional Classical guitars||flat (no radius)|
|Martin acoustic guitars||16" (406.4 mm)|
|Gibson acoustic guitars||12" (305 mm)|
Some of these manufacturers have changed their fretboard radii over the years, but this is a fairly accurate list of guitars. Obviously, if you do not know what radius your fretboard is, you can check it with a radius gauge. Simply take the strings off of your guitar and place the radius gauge directly on the fretboard. Look to see if light is shining between the radius gauge and the fretboard. If there is light shining through, you have the wrong size radius. Turn the gauge and try a new size until you can't see light shining through. The strings should be set to the same radius as your fretboard. This way the strings are just floating above the fretboard in the same semi-circle pattern.
Because there are a number of different kinds of bridges, setting the radius of the strings does not follow the same steps on all guitars. I will show you how to set the string radius on the most common electric guitar bridges:
Fender has made a variety of different bridges over the years. Mostly all Fender bridges have the strings resting on individual saddles pieces. This configuration makes it easy to adjust the radius of the strings. Simply take the correct size allen wrench, usually a 1.5mm, and tighten or loosen the setscrews holding the saddle pieces at an angle. Tightening the setscrews will raise the strings and loosening the setscrews will lower the strings. On the Fender style bridges, it is important to set the high e and low E string action first. Then place your radius gauge on the outside strings and adjust the inside strings up or down until they touch the radius gauge. See the action adjustment page for more information about setting the action on a Fender bridge.
Unlike the Fender style bridges, the Gibson or Tune-o-Matic bridges consist of two separate pieces. The strings are anchored in the "stop tail" and sit on top of the bridge piece. The bridge has individual saddle pieces like the Fender style bridges, but unlike the Fender style bridges the Gibson or Tune-o-Matic saddle pieces cannot be raised or lower by a simple turn of an allen wrench. It is not often that you will have to actually adjust the string radius on a Gibson bridge because they are "non-adjustable." This means that the saddle pieces are fixed in height. If you do have to adjust the string radius, you will need a file and/or nut file. The saddle pieces will have to be filed down until the strings sit in the proper radius.
First, you will need to remove the strings from the saddle pieces. You can slightly detune or release the tension on the strings, so you can pull the strings off to the side of the saddle pieces. Do not force the strings off the saddle pieces. You can break your string; or worse, you can break your saddle pieces if they are not made out of metal. Start with the middle strings: the D and G-strings. File down these two saddle pieces until they are level in height. You can use a file or nut notching file-- just keep the same shape of the saddle pieces. You want the saddle pieces to be the same angle and shape just lower. Once these saddle pieces are equal in height, you may put the strings back on these saddle pieces and place the radius gauge on them.
Second, file down the other saddle pieces slowly, according to the radius gauge. You do not want to file off too much off the saddle piece. File a little bit, replace the string, and check your progress with the radius gauge. I like to start with the A and the B-strings. Once those are adjusted, I move on to the outer strings. File down the saddles until the stings barely touch the radius gauge. Do not press the gauge down--just set it on the strings. If the outside strings are holding the gauge in the air and not allowing it to touch the middles strings, you need to file down the outside saddle pieces more. Be very careful. If you file down the outside saddle pieces too much, you will have to start over and adjust the middle strings again. Once you have filed down all the saddle pieces and replaced all the strings on the saddle pieces, the radius gauge should touch all of the string when place on top of them. You can then adjust the string action on the bridge.
The Floyd Rose style bridge is a completely different animal altogether. These bridges have individual saddle pieces like the Fender and Gibson style bridges, but the Floyd Rose bridge saddle pieces are not adjustable and cannot be filed down. The Floyd Rose saddle pieces are hinged to intonation pieces that are bolted to the bridge itself. The intonation pieces are the parts of a Floyd Rose bridge that actually set the radius of the strings. Much like the Gibson or Tune-o-Matic bridges, the radius on a Floyd Rose bridge rarely needs to be set. If you have measured the fretboard and strings radius and they are not the same, the Floyd Rose bridge will have to be adjusted.
To adjust the string radius on Floyd Rose bridge, you will have to take the stings off of the guitar and out of the saddles. Unbolt the locking nut and detune the guitar. You may notice that once you detune the guitar the bridge's tail end will start sinking and eventually bury itself in the body. You can eliminate this problem by pushing down on the whammy bar and placing a block of wood underneath the Floyd Rose Bridge. The block of wood will stop the bridge from being pulled back by the spring tension while you detune your guitar. For more information about how a Floyd Rose bridge works and how to set it up, please visit the Floyd Rose Bridge page.
Next, unbolt the intonation piece from the base of the bridge. Now, the entire saddle and intonation piece can be removed from the bridge. You will need to clamp the piece down either in a vise or clamp in order to file it.
Next, file the bottom of the intonation piece to lower the string height. As with the Gibson or Tune-o-Matic bridges, I would start with the D and G-strings. Once you have leveled those, bolt the intonation pieces back in the bridge, restring it, and measure the strings to make sure both the D and G-strings are equal in height. Repeat these steps with the A and B strings and then with the E and e strings.
A word of caution-- as you can see, this repair can be time consuming because you have to keep disassembling the bridge, reassembling it, restringing it, and measuring it. Make sure to file small amount of material off of the bottom of the intonation pieces at a time. You do not want to make a mistake and take too much material off the bottom of one of the intonation pieces and have to start over adjusting the D and G-strings. Take your time. If this repair needs to be done, it is kind of a pain. You don't want to get half way through it and be forced to start over because you took too much material off the bottom of one of the intonation pieces. But as I stated in the beginning of this section, Floyd Rose bridges rarely need the string radius adjusted. This is an infrequent repair if ever needed at all.
For more detailed information about the design and construction of these bridges, visit the electric guitar bridge page.