Pickers Coerner-Neck Relief and Trussrod Adjustment

Neck Relief and Trussrod Adjustment

by Pete Roehling

Pete Roehling is a member of the SWBA Member Band, Felonious Plunk, and a luthier at the east end of Redlands. Those wishing to contact him, can send e-mail to Peter_roehling@eeee.org.

O.K., so your instrument is strung with your choice of fresh strings and is tuned to correct pitch. You are now ready to check the neck for RELIEF. Relief is the small amount of bow that we actually want in a properly adjusted neck. (A fingerboard must have relief because the strings travel in a long shallow curve, and would strike the frets if the neck was perfectly straight.)

Trying to peer down the neck looks cool, but will actually gain you no useful information. Instead, we will use the first string as a straightedge to check the amount of relief. Begin under a good bright light. Sunshine or an unshaded light bulb work well. Indirect lighting or fluorescent tubes do not.

Fret the first string behind the first fret with your left index finger, then fret it also between the fourteenth and fifteenth frets using your other (right) index finger. While still pinning the string tightly, eyeball the string and the frets beneath it at the point half-way between your two fingers. A guitar or banjo should have .007" to .010" relief between the string and those frets. A mandolin is about half of that.

If you can't tell if there's any relief or not, move the instrument so you can see the shadow the string casts on the frets! A guitar's first string is .012 or .013, and a banjo's is .009 or .010, so you can use the string to judge the amount of relief. A "calibrated eyeball" is a big help if you have one.

If the string lies on the frets or has only a sliver of clearance, your neck is too straight and needs to be relaxed (more bow by loosening the trussrod). If there's more than the thickness of the first string, the neck is a bit too bowed, and the trussrod needs to be tightened.

If you have determined that your neck is in need of adjustment, then it's time to reset the trussrod tension, assuming that you have an adjustable trussrod. (Many inexpensive instruments have NO trussrod, or at best have one that cannot be adjusted. Oddly, this is also true of older Martin guitars and some Gibson mandolins.) Such instruments require professional help.

Providing you do have a trussrod nut, it will be found either on the headstock, usually under a cover plate; or beneath the fingerboard inside the sound hole. Some nuts accept Allen wrenches, some take hex sockets, and a few use Phillips screwdrivers. If you don't know what these are, or don't own any, you probably shouldn't try to adjust your own trussrod............

Therefore, heed these words of warning: All trussrod nuts tighten clockwise and loosen counterclockwise. Tightening the rod will straighten the neck and loosening it will allow more bow (relief). But the total play between the time the nut takes up tension and the time the trussrod breaks is often no more that one half turn! So if you begin to adjust the nut and it fails to move when moderate pressure is applied, STOP! Similarly, if the nut does turn but the neck fails to respond, STOP! Do not chance breaking your trussrod. If you do so, you will be in for several hundred dollars in repairs, and you may have to junk the instrument entirely. Always take the instrument to a professional repairman or luthier when the least doubt as to either the trussrod's condition or your ability to correct any problems. You only get one chance to do this right, which is why you no longer get a free trussrod wrench with your new instrument. Too many folks busted their trussrods and then asked the maker to repair the damage on warranty.

Assuming that everything works as advertised, adjust the nut in very small increments, checking for relief changes after every single tweak. This is because no two necks react quite the same way; some will move quite a bit with a very small amount of input, and some will not.