For a guitar equipped with a single string tree to hold the 1st and 2nd strings, the angle between the retainer and nut should be about the same as the angle between the nut and 6th-string tuner (Photo 4). For guitars that require a second string tree for the 3rd and 4th strings, the angle should approximate that of the 5th string.
Many string trees sit on a separate post or standoff spacer that determines the retainer’s height. The attachment screw passes through this washer-like cylinder and goes into the headstock (Photo 5). When the post is a separate piece from the section that actually holds the strings, you can adjust the retainer’s height—thereby controlling the string angle—by inserting a shorter or taller spacer.
If the string angle is too shallow and you have a removable metal or plastic spacer, you can increase the angle buy sanding or filing the spacer to reduce its height. Alternatively, you can substitute a shorter spacer: Electronic supply companies sell standoffs for PC boards, and some enterprising guitarists adapt the ball-ends of bass strings for this purpose. Stacking small washers can work too. Whether you need to go up or down, it shouldn’t be too hard to adjust the height of your string tree by either modifying it or swapping it out.
Replacing the string tree. If you opt to upgrade to a roller or graphite retainer, it’s a very simple project. All you need is a small or medium tip Philips head screwdriver. Lift the strings out from the retainer, remove it, screw the new one in place, and you’re done. You might encounter small variations in screw size and threading, but most manufacturers use a consistent size. You can use your original screw if it’s in good condition and fits the new retainer.
First-time installation. If you’re installing a string tree on a headstock that’s never had one—on a replacement neck, for example—string up the guitar and lay the new tree on the corresponding strings, midway between the nut and closest tuner. Confirm the strings are lined up evenly and then, with the screw in place, press down on the tree so the screw makes a small indentation in the headstock. This indentation should lie exactly between the two strings. Use it as a guide for drilling the mounting screw hole.
Start with a pilot hole, using a very small bit. For the screw hole proper, be sure to choose the correct drill bit—it should be slightly smaller than the screw. Measure everything twice, go slowly, and be careful how deep you drill—you don’t want to drill completely through the headstock! Before installing the screw, lubricate its threads with a bar of soap or candle wax.
Inserting a delicate screw into a hard maple headstock requires skill, so don’t attempt to install a new string tree unless you have the right tools and experience. If you’re unsure about your abilities, take the guitar to a qualified repair tech or luthier.Goodbye string trees. Some manufacturers offer locking tuners with staggered posts. Intended to create the required string angle on a six-in-line headstock without using string trees, staggered posts start out at a normal height for the 6th string and then gradually reduce height, which puts the shortest post furthest from the nut. Depending on the geometry of your headstock, you may be able to eliminate string trees altogether by using these tuners, but the only way to know for sure is to install them and see if you experience any of the sitar sounds or sustain issues that come from having too shallow an angle on your top strings. In most cases, you probably won’t need string trees if you have staggered tuners.