Truss Rod Adjustment

Paint Your Face Blue and Adjust the Truss Rod

Preventable Repair #2  The neck on your instrument is curved because the truss rod has been neglected.

There is a lot of fear involved in adjusting your instrument’s truss rod on your own even by those who think nothing of sky diving or playing their mando in front of a huge crowd.  When adjusting the rod the neck often makes snap, crackle and popping noises then you start to sweat while thinking, ‘what have I done!’.  Some of this fear is generated by a few horror stories that make the rounds. Mary may have contributed to this by this picture relating that the rod was sticking out of the back of the neck…

Yes, cringe worthy and anxiety producing however most adjustments are done with no problems at all. I posted it again because it’s very dramatic but mostly to show how important it is to keep an eye on the neck of your mandolin and keep up with needed adjustments. I believe that anyone and everyone should pay attention, at least monthly, to “neck health” and learn how to adjust the truss rod of their instrument. The picture above is an example of a truss rod that most probably was NEVER adjusted before, then an attempt was made to force straighten the necktrying to solve a problem created over years in a single hair rising sessionOver an extended period of time, if not corrected, the neck will settle into a position where the truss rod is no longer able to straighten, requiring some TLC from a luthier.

Why adjust the truss rod:  Environmental factors such as heat and humidity will expand and contract your instrument’s tone woods including the neck, affecting string height (action) and neck station. The strings exert pressure on the neck (and the top) pulling the peghead up towards the tailpiece. This string pressure is also the reason you should loosen the strings if your mando is going into long-term storage (be sure to dig it out of the closet or from under the bed to check the flatness of the neck periodically), or being shipped (with the possibility of taking a hit).

If your truss rod is not adjusted when needed (to keep the neck flat) eventually it will, at minimum, need a plane and re-fret and as worst case a new neck (as the picture above demonstrates).

In reality, the truss rod is your friend.  It was a great invention that will keep your neck playable.

When to adjust the truss rod:  Monthly, changing seasons, travel, storage, uncomfortable or hard to play, noticeable bow in neck. See trouble shooting below.

Be brave of heart, paint your face blue and charge through the directions below.

However, after reading this please free to call The Bruce if you need additional information or a pep talk. bruce@montanalutherie.com, 406-580-6053.

The correct order in basic setup:  Truss rod, Action, Intonation.

TRUSS ROD ADJUSTMENT

The neck should be near flat as you sight down or lay the edge of ruler down the length of the fretboard on both the treble and bass edges.  Under full string tension, just adjust the rod 1/4 turn at a time, checking the neck as you go.  The neck may groan and pop a little. If the neck is slightly twisted, use the first edge to reach true as a good place to stop.

1.  To take relief (bow) out of your neck, tighten the truss rod. (turn CLOCKWISE)

2.  To relieve hump in the neck, (rare, unless you’ve over tightened the rod) loosen the truss rod. (turn COUNTER CLOCK-WISE)

3.  If the rod will not move and you still have a bow, it would be best to visit a local luthier or send it to Bruce.

Check Action:  More often than not you’ll have to adjust the action (playability) after a successful adjustment session (the fingerboard is flat). Tightening the truss rod, bringing the neck back to true, will lower the action.  A good medium action on your mandolin is 1/16” from the top of the 12th fret to the bottom of the G string and a hair less on the E side.  Most mandolins will have some way to adjust your action at the bridge.  If you’ve over tightened the rod, the instrument will buzz on the first five frets at a good action.  

Check Intonation:  If you’ve done either a major truss rod or action adjustment, the intonation my need to be tweaked.  If the instrument plays sharp at the 12th fret, loosen all but the outside G and E strings and gently move the bridge towards the tailpiece checking the intonation on the outside strings as you go.  Small movements of the bridge will serve you well in this process.  If it plays flat, move the bridge towards the peghead.  When you are satisfied with the intonation you can bring the remaining strings up to pitch while insuring the saddle hasn’t started leaning towards the peghead as you go (we’ve had many sent in that turned out to be saddle leaning).

Note:  If you play with a high action, your bridge placement will be slightly closer to the fingerboard.

BASIC TROUBLE SHOOTING

If you’ve made sure that the fingerboard is flat and the action correct but are still having issues perhaps the information below will help you figure out the problem.

  1. Buzzing
    – While played open: action is too low, nut slots are too deep, or cut at the wrong angle. The nut should be replaced.
    -While fretting at a single fret:  the next fret is too high.
    -Buzzes on frets 1-5:  truss rod needs to be loosened and adjust action.
    -Buzzes on frets 6+:  truss rod needs to be tightened and adjust action.
  2. One or more strings sound fuzzy or won’t note clearly as played up the neck: slots in the saddle need to be recut at the correct angle.
  3. String goes sharp while playing: -String is sticking in nut slot:  first try graphite (pencil lead) in slots- slot may have to be widened or the nut replaced.
  4. String goes flat -String is sticking in bridge saddle slot:  first try graphite (pencil lead) in slot- slot may have to be widened or the saddle replaced. -Machine heads may be worn and slipping.
  5. Instrument will not intonate (If you’ve recently changed your strings make sure your saddle is not flipped, bass for treble and that the bridge is not sitting at a steep angle across the top of the instrument.If, while fretted at the 12th fret:
    -Plays flat:  move the bridge towards the peghead
    -Plays sharp:  move the bridge towards the tailpiece

I hope this helpful! Once again, don’t hesitate to call or email with any questions or concerns you may have.

Bruce D. Weber bruce@montanalutherie.com 406-580-6053

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