In most cases, the neck of a guitar is adjustable. Although the wood is generally hard, dry, and stiff, it will still bend with string pressure and humidity - or lack thereof. In our shop we have to deal with that issue on a daily basis. Inside the neck is a routed channel between the finger board and the neck shaft where a truss rod is placed to compensate for movement on the forward axis of the neck to add
stability. The rod is steel and is adjustable. It runs the length of the guitar neck, with an opening at one end allowing for adjustments.
The truss rod both strengthens the neck and facilitates an adjustment called "relief" in the neck. A bowed or humped neck can be reversed with skillful manipulation by the adjuster - you. All guitar necks are subject to great stress. This is sometimes the result of seasonal change, Other times when a neck could take on a slight bow or hump are due to string changes with gauges higher than normally used. A guitar player will usually know a little about how to make some adjustments on his guitar. Some things however may contribute to a misaligned neck.
Several of the "usual problems" seen are heavier gauge strings which increases the forward pressure, removing all of the strings at once, and leaving guitars in a hot car. These actions will cause immediate negative pull and the neck will revert naturally
back to where it started. However, if it does, there is a solution if you follow the procedure below for proper repositioning of a bowed neck. In our Custom shop this is the procedure we use.
First, loosen all the strings (you will not have to remove them). Push the loose strings to one side to gain access to neck adjuster. Remove the cover so the neck adjuster is exposed. It's either an Allen screw or a hex nut. Look down the neck from the top where the tuners are located towards the bridge (similar to sighting a down the barrel of a gun) to see how much of a bow or hump the neck has in it.
It is recommended to use a Notched Straightedge to see how far out of alignment the neck really is. The notches are on both side of the tool. One side has cutouts for a 24-3/4" scale neck and the other is for the most common 25-1/2" scale. They are there so frets can be avoided when the tool comes in contact with the fret board. The frets fit neatly in the cut out and the straight edge will show any problems when it lies straight on the fret board.
At this point, if it is discovered that the neck is out of adjustment, it's time to go to work. Insert the Allen key or hex wrench in the Allen slot or on the adjustment nut and turn very gently in small increments at a time. Checking the neck as you proceed with each nut turn is required. Once the neck is straight keep adjusting a bit more to compensate for the tension the stings will add once they are re-tuned to pitch. Turn right or clockwise for "bow"; alternately left or counter clockwise for a "hump". Take special care as not to tighten the nut too much because it could result in a broken truss rod, stripped threads and a much larger monetary outlay than originally intended.
This should fix the problem! If there seems to be an inordinate amount of "string buzz" that you find impossible to live with, bring it in to your guitar tech for further inspection. If the neck has a "twist" it can void the neck straightening process you have just used and will need attention from a luthier.
On some vintage guitars the adjustment is the same but in a different location. It is made at the end of the fingerboard called the heel or butt end.
Rick Mariner is the owner and founder of Haywire Value Priced Custom Guitars, and a member of the Association of Stringed Instrument Artisans (A.S.I.A.), as well as a guitar player. He holds a Bachelors degree from University of Maryland and a Masters degree from George Washington University.
Haywire developed an 8-Point "Gig-Ready" guitar process that allows for Haywire Custom Guitars that are "Gig-Ready". With many years of development and guitar set-up experience, they pride themselves in helping guitarists to build the "Just Right" Haywire guitar at prices well below market.