marksfretshop.com Guitar Repair Blog

Truss rod adjustment is a critical part of setting up a guitar up to play well. The purpose of the truss rod is to counteract string pull and help keep the neck straight. Truss rod adjustments are usually necessary when changing string gauge and often during seasonal changes in temperature and humidity. In most cases, truss rods are adjustable at the peghead on electric guitars or through the soundhole on acoustics. Truss rods normally adjust clockwise to tighten and counter-clockwise to loosen the rod. When a guitar comes in to the shop for a setup I usually remove the truss rod nut and add a small amount of oil to lubricate the threads and help the rod adjust more smoothly. Once I feel the truss start to snug against the shoulder, I make adjustments in small incements  (1/8 -1/4 turn) and recheck the neck/fret profile using a presicion ground straight edge. The idea is to adust the neck as close to straight while keeping in mind the arc of vibration path of the strings. Think of it this way…. a string vibrates in several directions but it is the up and down direction with which we are concerened. If a neck is set absolutely straight and with low action, then there’s a great potential for the string to contact the frets as it moves down toward the low point of its arc. You can prevent this by setting the neck for a slight amount of forward bow, called “relief”. The amount of relief will vary depending on string height, string gauge, fret condition, and player’s level of pick attack. Usually it will be as little as 0.002″ - 0.006″ (measured somewhere between the 7th - 9th fret) on electrics and higher on acoustics. It is important to remember the following:

1. The truss rod does not control the action of the guitar. It can help the feel and playability on the middle frets of guitars with too much relief.

2. Adjustment should be made in small increments, giving the guitar neck time to adapt to the change. Some necks react quickly, some will take more time.

3. If when tightening the truss you hear a popping or creaking sound, STOP! Take your guitar to a qualified technician to evalulate the neck. 

4. Some necks, like Rickenbacker or necks with dual action truss rods adjust differently. If you aren’t sure then you should consult a technician.

Replacing a broken or stripped truss rod is major surgery on most guitars and can be very expensive.

The cold weather months can be hard on your guitar, especially those acoustic instruments. Generally speaking, your guitar likes to be in the same environment as you. For cold and dry winter months it is best to use a case humidifier; such as a Dampit, or if you leave your instrument out of the case while in the house, try to keep room humidity between 40% - 50%. Instruments that have a nitrocellulose finish should be left in the case during transport. When moving from the cold into warm air, leave the instrument in the case and allow it to slowly acclimate to the new temperature. Not following this procedure will cause cold weather checking in the finish and possible top cracks on acoustic instruments. Have you ever picked up an instrument and found the fret ends to be sharp and sticking out? This is another effect from exposure to cold dry climates. In an environment that is too dry, neck woods have a tendency to shrink across their width while the metal frets don’t. This is fairly common in stores that do not properly regulate the humidity and with import instruments that are exposed to temperature extremes during international transport. This condition must be corrected by filing the fret ends. Rehumidification seldom ends in a satisfactory result.