Truss Rod Versus Saddle

Rich Cohen

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I've "inherited" my son Jason's Alvarez dred that I had given him in 2000. I put new D'Addarios on it on March 1st, 2019. I noticed the action was too high for me. Somewhere around 12 64ths at the 12th fret. So, I tweeked the truss road and brought it down to about 8 64ths. I would like to have it at 6 64ths, but I'm afraid to twist the trust rod much further. When does one give up on the truss rod and begin to sand down the height of the saddle to fix the action?
 

Velvet Phelts

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Although Truss rod adjustment can lower the action somewhat. That's not it's function. The function of the truss rod is to counter the pressure of the string on the neck. Adjusting the bow or the neck relief. String action is dealt with by Nut slot Bridge height, or neck reset. Changing the angle of the neck to the body. Turn the truss rod too much it will break, or strip. Then you've done it.
 

wileypickett

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You shouldn't rely on the truss rod to fix action problems. Though it can tweak the action a little, the truss rod is just meant to adjust the neck's resistance to the string pull, by adjusting the relief.

It sounds like you've probaby adjusted the truss rod as much as is prudent. Now tackle the saddle!

[Velvet Phelts and I posted at the same moment -- boy, are we on the same page!]
 

wileypickett

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What model Alvarez did you buy for your son? I have a cedar-topped Alavarez I got for nothing at a yard sale -- it's fantastic! First cedar-topped guitar I ever owned.
 

Rich Cohen

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You shouldn't rely on the truss rod to fix action problems. Though it can tweak the action a little, the truss rod is just meant to adjust the neck's resistance to the string pull, by adjusting the relief.

It sounds like you've probaby adjusted the truss rod as much as is prudent. Now tackle the saddle!

[Velvet Phelts and I posted at the same moment -- boy, are we on the same page!]
Good advice. I'll address the saddle situation next.
 

davismanLV

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What they said, ^^^. Truss rod is not to adjust the action and you can wreck a guitar torquing on the TR when it needs the saddle lowered. Truss rod is not for neck angle problems, it's for relief (curve/straight) in the neck. Once you decide how much you want to take down the action at the 12th fret, you then mark double that amount on each side of the saddle draw a line across and start sanding, checking along the way to make sure. If you've really cranked on the truss rod, you may want to back off a bit before undertaking the saddle lowering.
 

GardMan

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Before you do anything to the saddle, it would be best to get the truss rod adjusted properly. As mentioned in several posts, the truss rod provides an adjustable means to counteract the pull of the strings on the neck. Loosen the truss, the string tension will bow the neck forward (and coincidently affect the action). Tighten the truss, and the truss will counteract the strings and straighten the neck... unless you go to far, in which case it will introduce back bow).

Although neck relief is somewhat a matter of preference, Guild (used to) recommend a relief of 0.006-0.012". For a 14 fret neck (neck meets body at 14th fret), the measurement is made my putting a capo on at the first fret, then fret the string at the 14th fret and measure the gap between the top of the 7th fret and the string with a feeler gauge (if you don't have one... a light gauge treble e string is 0.012"). The strings DO need to be at tension when measuring...

If the string is higher than that, tighten the truss a little (turn CW about 1/6 to 1/4 turn) to straighten the neck a bit... If it's lower than that, then loosen the truss a little (turn CCW about 1/6 to 1/4 turn). Remeasure and repeat as needed. I DON'T loosen the strings when adjusting relief... I know some folks do... but I haven't had any trouble turning the rod's nut with strings at tension.

Once the neck relief is set "to spec," then check the action and adjust it to your preference by adjusting the saddle.

It's not rocket science, but does take patience...
 

dreadnut

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The function of the truss rod is to adjust the camber of the neck, not to straighten it or bring the action lower.
 

Br1ck

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How much saddle do you show above the bridge? If it is already low, it's time to assess the neck angle.
 

GardMan

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The function of the truss rod is to adjust the camber of the neck, not to straighten it...
I have never heard the term "camber" used to describe the action of the truss rod... but the google definition equates camber with a convex or arched shape... so it would be a reasonable use of the word.

The rod does affect the curvature of the neck, and the curvature determines what we often refer to as "relief." If (a single action) truss rod is too loose, the neck can be pulled forward by string tension (this would be concave, if looking at the fretboard), increasing the relief. If too tight, the neck can be bent into a back bow (convex, looking at the fretboard). It is my understanding and experience that the changes in curvature happen along the the entire length of the neck, or at least the portion of the neck affected by the truss (which excludes everything above the neck joint).

In that regard, adjusting (tightening, if too loose, or loosening, if too tight) the truss rod CAN be used to straighten/flatten the neck... or at least the portion of the neck that is affected by the truss. There are some players who prefer to have their necks as straight/flat as possible... but most specs allow for some relief, or forward bow. Back in the Westerly days, I believe Guild's specs were 0.006" - 0.012".

Relief should be set by adjusting the truss rod BEFORE adjusting action at the saddle.
 

Rich Cohen

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Thanks a lot to all those offering advice on this question. Now, I'm a bit clueless as to what's the "benefit" of spec-ing the neck as straight, convex or concave? If it's really an adjustment of the saddle that will lower the action, then what help in that regard is the truss rod, if any?
 

GardMan

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The strings are anchored at each end, and need room to vibrate without touching the frets (which would cause a buzz). The actual waveform is quite complicated, but suffice it to say, the strings need more room above the frets in the middle of the string than they need near the ends (since the ends are fixed).

If the neck has back bow (convex, when looking towards the fretboard), frets in the middle of the neck will appear higher than the saddle and nut... the strings might even rest on the middle frets. The strings will buzz, almost guaranteed....

If the neck is dead straight/flat... strings will (usually) be closer to the frets, requiring less pressure to fret. Since strings will be stretched less when fretting, intonation might be better. On the other hand, a straight/flat neck requires a light attack (fingerpicked, or good pick technique) to avoid having the strings hit the frets, causing them to buzz.

Adding some relief (forward bow, concave when looking at the fretboard) gives the strings more room to vibrate w/o touching the frets. Too much relief will make it harder to fret as you move up the neck, as well as throwing off the intonation.

So, its sort of a trade off... you want sufficient relief (in the form of forward bow) so the stings can vibrate cleanly, without so much that fretting is more difficult and intonation is affected.

Once you have the relief properly adjusted (to factory spec, or your preference), you then set the action at the (nut and) saddle... remembering that lowering (or raising) the strings by 1/64" requires lowering (or raising) the saddle by TWICE that amount.... 1/32" in this example.
 

HeyMikey

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As was mentioned check the nut slots for proper height. If it was never professionally set up these are often overlooked. Adjust the truss rod for desired relief. Sand the bottom of the saddle. Level frets.

If the saddle is very low and you don’t like the break angle you can extend the string peg slots toward the bridge if you don’t plan to go the neck reset route. However that is more invasive in nature so some people don’t like to do it.
 

Velvet Phelts

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There's where we differ. I won't sand the bottom off a saddle. I want each string at a specific height. Sanding the bottom won't give you that kind of precision.
 

HeyMikey

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There's where we differ. I won't sand the bottom off a saddle. I want each string at a specific height. Sanding the bottom won't give you that kind of precision.

Yep you can do it that way also. I first manage individual string height at the nut. For general sting height I manage that from the bottom. You can certainly do it from the top of the saddle for fine tuning individual height and compensating intonation.
 

dreadnut

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All necks should have some camber, like a ski. The truss rod adjusts this. It does not adjust the neck angle at all. I can't imagine having the neck perfectly flat.
 

GardMan

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I can't imagine having the neck perfectly flat.
I can't either. But, if you believe what you read on AGF and UMGF, some players like "flat" (no relief) necks...
 

nielDa

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Rich - What GardMan and others said - adjust the neck bow first. Also check the “bellying” of the top of the guitar. Humidity can affect it, and if you suspect it may have been stored in low humidity it may require storing it in a way to bring it back up. Usually humidity is not a problem in the summer, but could be a factor.
 
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