Most stringed instrument necks are fashioned from wood. Wood is a remarkable medium. It’s cellular makeup gives it its unique ability to absorb and transmit energy efficiently, and depending on the particular species, wood can transform vibration into sounds and tones that have pleased and titillated the senses since the beginning of recorded history. Like just about everything else on this planet though, wood has its flaws and shortcomings. Wood maintains a symbiotic relationship with its surroundings…it both responds, and reacts to the elements…but even more so when it’s extracted from its natural habitat (eg) cut, dried out and fashioned into implements like furniture and musical instruments. Although in its natural live state, wood marvelously withstands the five natural physical forces : compression, tension, shearing, stretching, and twisting, when it dies, dries out, and changes shape…it needs some help. Guitar necks, especially older, worn and aged maple necks feel soooo good when we run our hands up and down their surface which has darkened and been burnished by years of use. The problem though, is that not very many of these bare, unprotected guitar and bass necks remain stable, or render predictable service in the long run, especially during the Spring and Summer seasons. This is a primary reason why we apply protective finishes to musical instrument necks. The finish is a barrier…kind of like the bark on the tree the wood originally came from. It helps to slow down the wood’s natural tendency to absorb moisture and contaminants into its pores and cells. Let’s think of wood as a big, thirsty sponge that sucks up everything around it and swells up during the process. This swelling is caused by the wood fibers and cells taking in moisture which results in tension that translates into energy. Basic physics tells us that applied energy does not remain static. It has to go somewhere, and when the energy is compounded by the induced stresses of string tension…another form of energy, a guitar neck can, and will do many things. The neck wood will swell and increase in size, it’ll change it’s shape, and it’ll move in different directions, usually starting at the point of least resistance. How do we counteract, or impede all these phenomena ?
The Truss Rod
The intent of a neck adjustment rod, or “Truss Rod” is to counteract the bending and compression of wood fibers caused by the application of multiple forces (eg) guitar and bass strings, humidity, cold and heat. on the neck. Would you believe that a set of electric guitar strings in the gauge of .010 – .046 when tuned to standard pitch at an average scale length of between 24.75” and 25.5”, and depending on the brand of strings can yield in the neighborhood of 100 pounds of continuous tension? By adjusting the Truss rod, we exert forces that help to lessen the tremendous stresses applied to the neck wood by string tension and the weather.
The relentless humidity and heat of the Spring and Summer months can play havoc on stringed instruments. If the strings rattle , buzz or fret out…if you notice dead notes, if the action changes drastically, and/or the instrument will not intonate, it’s time to have the instrument evaluated by a qualified technician or professional Luthier. The aforementioned symptoms may indicate an over-adjusted truss rod. During the dry and cool fall and winter months when the neck wood was contracted, the adjustment was fine, but now that the weather has changed, it may be time relax the rod adjustment, and if the instrument has a screw-on neck, shims may have to be removed from the neck pocket. Here’s a simple check you can perform to see if the change of season and climate has affected your guitar’s neck.
Reading The Neck
Place the instrument on a flat surface, free of anything that could damage or mar the finish of the wood. First: The Bass side of the neck should be at eye level…you’ll be looking across the neck from side to side. Press the bass E string down on the first and last frets and then look at the middle of the neck. Ultimately, there should be a very small amount of space between the string and the frets…no more than about .015”, or about the thickness of a medium gauge guitar pick. If the strings are flat against the frets, it may be time for an adjustment to relieve some of the tension on the truss rod. Repeat this test using the G and high E strings. The amount of clearance across the neck when depressing the Low E, G, and the High E strings should be about equal. If let’s say….there is some string-fret clearance under the low E string, and there is NO clearance under the G or the High E string, it might indicate a twist or warp.
If all this technical stuff interests you, then you need to attend one of my seminars. You’ll get to see a real neck adjustment, and a good set-up. Don’t get any bright ideas though…I still won’t accept any responsibility if you mess up your instrument, and you’ll have to sign a disclaimer and waiver in order to attend.
Now….puleeez don’t log onto any guitar tool websites and buy yourself some neck adjustment tools just yet…there’s a lot more to properly adjusting a guitar neck than turning nuts, bolts and screws….and here’s where I print my disclaimer. I really hate to post stuff like this :
The purpose of this technical article is to entertain and inform the reader. It should not be construed as an instruction manual or a tutorial. Any attempt to change the setting on a stringed instrument neck adjustment rod or “Truss Rod” can permanently damage the instrument. Improper adjustment of the truss rod can render the instrument unplayable, it can severely damage the neck AND the body joint in certain instances, break, or snap the truss rod, or even destroy an instrument neck. Master Luthier George Goumas, the Fretshop, and The Fretworks warn explicitly against attempts to make adjustments to an instrument’s neck adjustment rod by un-trained and/or inexperienced persons. I will not accept any responsibility for damages incurred to an instrument by anyone other than myself.