Why Not Adjust Action With Truss Rod?

[John Arnold]

The classic mistake is to adjust the truss rod to compensate for seasonal variation in the action. That is almost always due to movement of the top, rather than an actual change in relief. As Bruce suggests, the correct remedy for this is to adjust the saddle height.
I have literally owned guitars for decades without touching the truss rod, once they have undergone an initial setup.

[mirwa]

Originally Posted by bausin

>> How does one even measure .007?

I use paper of known thickness.

I use feeler gauges and a flat edge when measuring relief, typically I set relief on guitars I do setups on, between 1 and 4 thou clearance on the 7th or 9th fret, subject to the truss rod fitted.

Steve

[The Kid!]

Originally Posted by Bruce Sexauer

There is an ideal relief for a given action height, and it is different for each string. My specialty is low to medium action. On a low action set up (1.8/32 x 2.6/32 at the 13th barred at the first) ideal relief is not visible on the high e string when stopped at 1 and 20, but can be discerned audibly by tapping on it mid-fingerboard. No click=too flat, visible gap=too high. At the same time, low E stopped at 1 and 20 should have 1/3rd to 1/2 the thickness of the high string visible around the 6 to 8th fret. The other 4 strings can interpolate these clearances with great success. This is what makes a guitar play GReat. If you so much as wiggle the truss rod the set up is ruined. I no longer ship truss rod wrenches with my guitars because of the number of times I have heard about how badly one of my guitars works, had it shipped to the shop, and found out the customer (or their friend) has messed with the relief. Readjusting the rod returns the playability 9 times out of 10.

Once a new guitar has stabilized to the string tension (not as much as a week), it is the rarest thing for a correctly adjusted truss rod to need further attention unless string gauge is changed. I usually ship my guitars with an extra saddle in the case, slightly higher than the fitted one. IF it turns out that the guitar needs a lower one, the higher one should be altered rather than the fitted one, as it was as close to perfect as I could make it at the humidity level when shipped.

Medium action has slightly more relief, by the way, but only by a couple of thou. Medium strings, on the other hand, can have a slightly lower action but with the same relief . . . Which may require a tiny (10th turn) adjustment on the LMI sourced TRST single action rod I favor.

PLEASE DO NOT ADJUST ACTION WITH THE TRUSS ROD.

I have winter and summer (just in case I need them) saddles for both of my gigging acoustics. I keep the guitars in their hard cases with 2-way humidipaks between gigs to keep them properly humidified.

I don't get much movement, but If I do, I'll swap a saddle before I go changing relief to change the action. Anything more than a saddle swap and a slight change in relief goes to my tech.

[JDaniel]

Originally Posted by mirwa

I feel terminology’s are at play here.

Adjusting relief will increase or decrease the arc of the neck in respect to the string line, adjusting relief can have an effect on the string height but does not lower the action but it can alter the action.

Example pre adjustment, 5 thou clearance at nut 50 thou clearance at 7th fret, 60 thou clearance at 12th fret, adjusting the truss rod, this can become 5/30/55, it’s most effective point of difference is around the 7th fret with adjustments.

Action is a relationship between the stringline and the neck at all fretted locations.

Example a persons action may be 5 thou string clearance at the 1st fret, 35 thou at the 7th, 60 thou at the 12 th fret, lowering the action vee the saddle, still closely maintains the original relationship at all fret locations albeit lower, now with a saddle tweak it’s 4.5/30/55, the exact same relationship is still there just lower, this is IMO a lowering of the action.

Setting the action up to start with, is with respect to all parts, truss rod adjustment, nut height, saddle height. However once these parameters have been set and identified for that customer, this is now their action, raising or lowering their action is subject to nut or saddle tweaks

Steve

Very clear explanation. I've always considered relief to be the accommodation of the amplitude of the vibrating string at constant tension. The top of the frets follow this curve; then the nut and saddle move the string away some satisfactory distance from the frets to set the action.

[murrmac123]

Originally Posted by Bruce Sexauer

. On a low action set up (1.8/32 x 2.6/32 at the 13th barred at the first)

You lost me right there Bruce ... I honestly have no conception of what these figures even mean.

Any chance you could convert them to thousandths of an inch, for easier visualization?

[Rodger Knox]

Originally Posted by John Arnold

The classic mistake is to adjust the truss rod to compensate for seasonal variation in the action. That is almost always due to movement of the top, rather than an actual change in relief. As Bruce suggests, the correct remedy for this is to adjust the saddle height.
I have literally owned guitars for decades without touching the truss rod, once they have undergone an initial setup.

See that Gibson in my signature? I've had it since 1964 and the truss rod cover has never been removed.

[John Arnold]

Any chance you could convert them to thousandths of an inch, for easier visualization?

1.8/32:
Divide 1.8 by 32 = 0.056"
Similarly, 2.6/32 = 0.081"

[bausin]

>> On a low action set up (1.8/32 x 2.6/32 at the 13th barred at the first) ...

Bruce,

What do those two numbers mean? Are they the range for what you consider low action, or are they the action at the 1st and 6th strings?

Also, why the unconventional action measurement, i.e. barring at the 1st fret and measuring at the 13th?

[murrmac123]

Originally Posted by John Arnold

1.8/32:
Divide 1.8 by 32 = 0.056"
Similarly, 2.6/32 = 0.081"

Thanks, John.

It would be simpler if we all just used Roman numerals ...

[Bruce Sexauer]

I see I was (once again) making assumptions, this being the build and repair subsection.

One barrs at the first fret and measures at the the 13th fret to eliminate the possibility (probability) of an inaccurately adjusted nut. Martin “standard” 12th fret measurements are generally quoted as 2/32” on the e and 3/32” on the E (where e is skinny string and E is fat string). Because I choose to pursue personal mastery though feel to the degree realistically possible, I judge relief by eye. I can easily approximate 5ths or 1/4s by eye looking at 32nds on a ruler, so I think in terms like 1 and 4/5ths thirty seconds, more easily written as 1.8/32”, which is the clearance Eric Schoenberg seems to favor on his high e string with a perfectly adjusted nut and negligible (but present) relief.

Eric’s playing style is not particularly dynamic compared to my own, being IMO between 3 and 6 on a scale of ten. I tend to play between 2 and 11, so historically I run a higher action than he does, which I describe as 2.2/32 x 3.2/32. As I mature and get better control of my exuberance, playing from 2 to 10 perhaps , I find I am increasing happy with just the slightest hair (lay terminology) under Martin standard, though nowhere near as low as Eric. If you are following this (all quite serious) then you can start to realize how subtle a really good playing set up is, and why a person blinding twisting on the truss rod can be so frustrating to some of the more in tune techs.

[N+1]

Originally Posted by Bruce Sexauer

you can start to realize how subtle a really good playing set up is, and why a person blinding twisting on the truss rod can be so frustrating to some of the more in tune techs.

I think we can all see that. We are dealing with tiny changes. But I don't think anyone contributing to this thread is likely to be 'blindly twisting on the trust rod', are they? Rather, we would be thinking of small reversible fractions of a turn, changing the relief by one or two thousandths of an inch at a time, trying to get closer to that optimum value - which may, as a helpful bonus, lead to a drop in the action that sparked off the idea in the first place.

[murrmac123]

Originally Posted by Bruce Sexauer

One barrs at the first fret and measures at the the 13th fret to eliminate the possibility (probability) of an inaccurately adjusted nut.

Unless of course one has already used the correct tools to put the plane of the base of the nut slot in the same plane as the plane of the first two frets (with the guitar adjusted to zero relief) in which case one can dispense with the capo on the first fret and go straight to dealing with the 12th fret.

[mirwa]

Originally Posted by Bruce Sexauer

My specialty is low to medium action. On a low action set up (1.8/32 x 2.6/32 at the 13th barred at the first)

I would concur, that is a low action for an Acoustic.

Steve

[Bruce Sexauer]

Originally Posted by murrmac123

Unless of course one has already used the correct tools to put the plane of the base of the nut slot in the same plane as the plane of the first two frets (with the guitar adjusted to zero relief) in which case one can dispense with the capo on the first fret and go straight to dealing with the 12th fret.

That’s it Exactly.