Truss Rod - stupid question?
- Thread starter Aarfy
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adorshki
Reverential Member
Hi Arfy. Actually the truss rod adjusts the flatness of the fretboard, it has nothing to do with neck angle.
The pivot point for neck angle is the joint itself. The tension of the strings pulls on the neck, bringing the headstock closer to the bridge, and the neck joint is the "weak spot" where compression and deformation occur.
The truss rod is contained entirely in the neck, so as the neck is pulled forward, the trussrod is pulled with it. It can't exert any counter-acting force on the joint itself.
The neck itself also flexes slightly under tension, but with no string tension it's actually slightly "back-bowed". That's so the neck (or more precisely the fretboard )will be brought flat under string tension at pitch.
This chart may help explain why adjusting the rod does have a slight effect on action, but it's secondary and very limited:
So if the neck's diving into the top, then adding some "back bow" (tightening the rod) will tend to bring the action height down, but again, only slightly. It's not actually changing the neck angle.
The truss rod also controls "relief", where a small amount of up-bow is desirable to allow the fretted strings to clear higher frets to prevent buzzing.
Hope I explained that well enough.
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wileypickett
Senior Member
I was afraid of adjusting truss rods for many years, but as I got familiar with what the job of the truss rod is, I was better able to tell when it needed adjusting, and I got comfortable doing it. (It's like being able to change a flat tire -- it's not hard to do and can be considered part of general maintenance.)
Print out Al's chart and keep it in your guitar case.
And go slow.
Print out Al's chart and keep it in your guitar case.
And go slow.
I'm STILL afraid!
walrus
walrus
Teleguy61
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Truss rod adjustments are a seasonal thing, as temps and humidity levels change, necks bow or straighten.
Once the bridge is correctly adjusted, correct and most comfortable action is maintained through truss rod adjustment, I find.
Once the bridge is correctly adjusted, correct and most comfortable action is maintained through truss rod adjustment, I find.
chazmo
Super Moderator
Do not fear it. Try 1/4 turn during different seasons and see if it helps. Again, small adjustments.I'm STILL afraid!
walrus
adorshki
Reverential Member
Actually, with flattops, and especially with mahogany* necks, the necks don't change shape as much as the top itself: when it gets dry it tends to shrink, which lowers the bridge/saddle and adding some back bow to the neck helps compensate for that. Vice versa in the humid season to the point that some folks even keep a different saddle for each "season".
But the necks themselves are relatively well-sealed from humidity by the finish and the glue in the neck joint. Fretboards, being typically "unsealed" can shrink, though, causing fret-end protrusion.
With bolt-on solid necks on solid bodies, the entry point for humidity is through through an unsealed attachment point, like seen on the end of this Taylor neck:
So those necks are more exposed and will show the effects of P-Diddy, er, humi-diddy.
* 'Hog is a very dimensionally stable wood across a wide range of humidity.
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Guildedagain
Enlightened Member
Truss rod adjustments should only happen if the "relief", typically .010", is out of order.
Hold down the low E at the 1st and 12th fret, look under the string, do you see a slight gap?
Conversely you can tap the string with your right hand thumb at the 8th fret, you can hear the clearance, like a wee hammer on/pull off.
Too much gap and the TR is too slack or the strings are too big.
Too little gap and the TR is too tight or the strings are too small.
Adjust as needed. The old time Guild owner's manual says to do this "at full string tension."
I ALWAYS begin a TR adjustment by backing it off, because the nut is often frozen in place, not a good way to start tightening something, but a good way to snap it off. Crack it loose in CCW direction, I unthread the nut most of the way, blow out the dust, and put a drop of fine machine thread oil on the thread. Bring the nut back down, seat it, and then tighten as needed.
Get a nice 24" heavy rule, the handy one for checking neck angle, lay it over the frets, you can see a lot this way.
On my JS2 bass, the neck has a very noticeable dip with no strings on at all, the neck is permanently bowed and even cranking the TR all the way - 1/2 turn from just seated - doesn't change a thing.
My 1972 Martin D28 didn't have a truss rod and I never gave it a 2nd thought.
Leo didn't feel that he needed one in the Broadcaster/Telecaster, but people like to tinker, so he put it in, under pressure from Forest White and others.
Hold down the low E at the 1st and 12th fret, look under the string, do you see a slight gap?
Conversely you can tap the string with your right hand thumb at the 8th fret, you can hear the clearance, like a wee hammer on/pull off.
Too much gap and the TR is too slack or the strings are too big.
Too little gap and the TR is too tight or the strings are too small.
Adjust as needed. The old time Guild owner's manual says to do this "at full string tension."
I ALWAYS begin a TR adjustment by backing it off, because the nut is often frozen in place, not a good way to start tightening something, but a good way to snap it off. Crack it loose in CCW direction, I unthread the nut most of the way, blow out the dust, and put a drop of fine machine thread oil on the thread. Bring the nut back down, seat it, and then tighten as needed.
Get a nice 24" heavy rule, the handy one for checking neck angle, lay it over the frets, you can see a lot this way.
On my JS2 bass, the neck has a very noticeable dip with no strings on at all, the neck is permanently bowed and even cranking the TR all the way - 1/2 turn from just seated - doesn't change a thing.
My 1972 Martin D28 didn't have a truss rod and I never gave it a 2nd thought.
Leo didn't feel that he needed one in the Broadcaster/Telecaster, but people like to tinker, so he put it in, under pressure from Forest White and others.
adorshki
Reverential Member
And "righty tighty, lefty loosey" when viewing the adjustment nut dead on. 1/8 to a 1/4 of a turn at a time, and give it overnight to "settle".
Just remember tightening adds back bow, but too much tightening can be disastrous. You should feel significant resistance to turning if it's too tight.
adorshki
Reverential Member
I thought those had a truss but aren't adjustable?
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When Tom Jacobs is about an hour away from me I'd be crazy as . . . .I'm STILL afraid!
walrus
to touch a truss rod. I'm great at correctly positioning truss rod covers, however, but there's not enough demand for that for Mr. Jacobs to take me on as a partner.adorshki
Reverential Member
Guildedagain
Enlightened Member
On the old D28 I think no truss rod at all but could be wrong.
The pesky fret-end protrusion you speak of is sometimes aptly described as "fret sprout". It is an indication of a dry guitar, but even properly moisturized, often it needs to be physically removed with a special file. Wood shrinks of the course of decades as it ages.
I've gotten very good at this as I've had to deal with it on so many guitars.
The one and only time I ever had it professionally deal with it went like this.
I scored a fairly priceless Korina V, custom made for Mike Zinke of the now long forgotten Mike Zinke band that rocked the Northwest back in the day. I'd never dealt with fret sprout before, and didn't want to f it up, so I took it down to the best luthier in town, a really nice guy who actually builds lutes.
After bugging him for about 2 months, he said it was ready to pickup, and big bonus he says he " leveled the frets, recrowned" the bill was a lot higher than I was hoping it was going to be... so I went downtown to pickup the guitar, pulled it out, and instantly noticed that the frets were sticking out every bit as bad as when I brought it in... ;[
It was embarrassing but I was like "Hey Rick, these frets are still sticking out", and he was like "Oh yeah, that's why you brought it in, huh" ding ding ding... Nice guy, but a bit of an absent minded professor.
So he whittled the fret ends right in front of me, and that's how I learned. He had a small Bastard file with the edges sanded flat smooth on a belt sander, which pretty easy to do if you have a belt sander, but me I have a special made Japanese file that does this, and you just shut out the world, get into the zone, feel and file and you end up with a neck that is as smooth on the edges as a baby's behind ;]
The pesky fret-end protrusion you speak of is sometimes aptly described as "fret sprout". It is an indication of a dry guitar, but even properly moisturized, often it needs to be physically removed with a special file. Wood shrinks of the course of decades as it ages.
I've gotten very good at this as I've had to deal with it on so many guitars.
The one and only time I ever had it professionally deal with it went like this.
I scored a fairly priceless Korina V, custom made for Mike Zinke of the now long forgotten Mike Zinke band that rocked the Northwest back in the day. I'd never dealt with fret sprout before, and didn't want to f it up, so I took it down to the best luthier in town, a really nice guy who actually builds lutes.
After bugging him for about 2 months, he said it was ready to pickup, and big bonus he says he " leveled the frets, recrowned" the bill was a lot higher than I was hoping it was going to be... so I went downtown to pickup the guitar, pulled it out, and instantly noticed that the frets were sticking out every bit as bad as when I brought it in... ;[
It was embarrassing but I was like "Hey Rick, these frets are still sticking out", and he was like "Oh yeah, that's why you brought it in, huh" ding ding ding... Nice guy, but a bit of an absent minded professor.
So he whittled the fret ends right in front of me, and that's how I learned. He had a small Bastard file with the edges sanded flat smooth on a belt sander, which pretty easy to do if you have a belt sander, but me I have a special made Japanese file that does this, and you just shut out the world, get into the zone, feel and file and you end up with a neck that is as smooth on the edges as a baby's behind ;]
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adorshki
Reverential Member
YOU've got a good repairman.
Nuuska
Enlightened Member
Oh my oh my
I've been such a bad boy for decades - whenever there was a substantial bow I simply turned as much it needed right at first try. Fine tuning later, if necessary. BUT - my trick was/is to stand the guitar on floor between my knees and pull the neck back with my left hand to relieve the tension of the rod - this is to save the thread from cutting - and then turn the nut w right hand as much as needed. On some guitars, that have been neglected it might be 2-3 full turns...
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adorshki
Reverential Member
I case it's good to know going forward, and assuming this guy on the UMGF knows what he's talking about, this is what I got when I did a formal search:
"Basically, all Martins have a truss rod.
The questions are what's it made of, and is it adjustable. Summarizing the history, without having the book to hand to get the dates....
Way back when, they had ebony non-adjustable truss rods
Then later, but still before WW II, T-bar truss rods, non-adjustable
Back to ebony, non-adjustable during WW II
Back to T-bar, non-adjustable after the war. (I seem to recall there were two different T-bar types in this era, but won't swear to that)
Square tube, non-adjustable in the 1970s and early 80's"
That was from post #10 in this thread: https://umgf.com/no-truss-rod-t116637.html
Only knew about the "non-adjustable" bit myself because I got it from a Martin snob at Guitar Showcase. He was a salesman in the acoustic room who didn't think anything was as good as a Martin.
Since they didn't have any Guilds on the wall, I guess he can be forgiven for that.
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adorshki
Reverential Member
On some guitars, that have been neglected it might be 2-3 full turns...