Best Quality DA Truss Rod?

[Rôckhewer]

You don't need any additional clearance at the sides, only the area under the adjustment nut

Right... but the round sides are indicative that there was a drill bit or burr ran in there... which would have cleared underneath as well.
(It was an early build... memories are fickle)
But... it is something I do now...because I've been using BBG rods.. and they have a bigger nut.

Alas... no point in forensic speculation.
I will have it back in my hands in a week or so.
If there's any scuffing on the wood under the nut...from the nut.. that might tell the tail.

 

[Bruce Johnson]

Or did I... ??
Look at the round under-cut on the sides of the channel.
I'm pretty sure I ran a drill bit in there to open up around the nut.View attachment 4144924

If it had been seriously binding up in the wood channel, then the over-torque would have rounded out the hex socket. But look at the end of the rod attached to the nut. That's a straight twisting shear-off. The nut obviously turned in the wood as it was being twisted off.

The only possible fault of the truss rod that I can imagine is if the threads are seized up. Not likely, but it could have happened. But still, the owner shouldn't have twisted it off.

When you get the truss rod out, check and see if the rod still turns.

 

[Freekmagnet]

Hmmmmmm....
Well... this just in.
THIS.... is an LMI rod ... if memory, and visual recollection serves.
It's installed on my third build (Alembic K Tribute)
View attachment 4144520
That was about what... 6 years ago?
Today?... well.... $#(!!!!... here's yer sign.
View attachment 4144521
So yippee frickin skippy.... I get to pull a board... and replace a rod.

Where do you get them fancy titanium jobbies?

I wish there was an “Not Like” option on the forum for this.

 

[Beej]

@rudy4444
How would you make it removable, just keep running the truss rod slot until it "daylights" out the headstock as it pitches downward? I actually thought of doing that on my current build, but it would require a really long TRC. I suppose it wouldnt be too difficult to extend the trussrod slot after the fact if it broke, to provide a path to pull it out. I have cut a 3/8" slot at the head for my 1/4" rod, but only to allow easier access for the hex key. The wider slot gives the hex key more turning space. Are you saying the 3/8" slot should extend the full length of the adjuster head, even if that passes under the nut?

I would say yes to this. I always clearance the nut area of the TR out to 3/8 wide all the way back to where the nut connects to the threads so it has full clearance. I also rout it 1mm deeper under the nut in that area for clearance and to prevent binding from when the TR angles when tightened up. This extra clearance is one of the main reasons I like to use a volute on the back for extra protection as well.

 

[Rôckhewer]

The only possible fault of the truss rod that I can imagine is if the threads are seized up. Not likely, but it could happen. But still, the owner shouldn't have twisted it off.

They weren't seized... Owner says he turned it slightly looser ... before trying to tighten.
He initially said he did a 1/4 turn.
I was like...damn... that's a lot!... he amended that statement to 1/8 turn. .... well... ok.
I have a suspicion that the strings were at tension when he did it....
But... there's no need to throw shade or argue... Because he has offered to pay for the repair.
(What does that tell ya...?)

 

[Gilmourisgod]

He damn well should pay for it, you have NO IDEA what shenanigans the previous owner got up to, a lot of people seem to think a truss rod should be able to flatten a neck under full string tension, and it might, but I Always detune a little and “help” the rod with light pressure on the headstock.

 

[Bruce Johnson]

One of the reasons Fender uses a small hex socket size in their truss rod nuts is so it acts as a mechanical "fuse". To keep users from breaking the truss rod. You have to use a small length wrench on it, and if you find a way to torque it too hard, the socket in the nut strips out before you can apply enough torque to break the truss rod off. Most of the time anyway. Then the repair is simpler: Back out the damaged nut, replace it with a new one, and the truss rod is working again!

But it's not any stronger than it was before. And the neck is still warped. With good technique, you can apply more torque to the new nut.....and now the maple behind the nut and at the anchor crushes back. That's the 2nd level fuse. And the neck is still warped, dang it! If you are experienced at this, you recognize the feel when the nut runs out of threads and locks up. Back off the torque before you break it!

So, you put a couple of washers behind the nut to gain back some more threads. Which doesn't make the truss rod any stronger than it was. And the neck is still warped. Put a longer bar on the Allen wrench, clamp the neck in a vise, take a deep breath, and give it everything you've got. And there's that satisfying feel when the rod finally twists off!

Now, go on TalkBass and complain about why Fender doesn't use higher quality truss rods!

 

[rmichael]

They weren't seized... Owner says he turned it slightly looser ... before trying to tighten.
He initially said he did a 1/4 turn.
I was like...damn... that's a lot!... he amended that statement to 1/8 turn. .... well... ok.
I have a suspicion that the strings were at tension when he did it....
But... there's no need to throw shade or argue... Because he has offered to pay for the repair.
(What does that tell ya...?)

Actually, what I amended the statement to, was that I backed the rod off approx 1/8” and then I went approx 1/4” (which technically was actually in two increments over approx 10 - 15 minutes) so it only turned an additional 1/8” over where it was when it seemed seized. What’s more, when I backed the truss rod off the sound of the friction between the wood and the rod was highly “audible” so I think it was seized. The measured string action at the 7th fret prior to making the adjustment was 2mm which was way to high for my hands with my medical issues.

Second, I make it a practice to always detune approx 1 whole step before adjusting the truss Rod and then retune after the adjustment.

Third, I offered to pay for the repair because this is a “used” bass that I purchased from another individual “and” you had told me in the past when I was placing my first order with you “that you do not offer any formal warranty on your basses”.

On top of being a mechanical engineer, I’ve been doing guitar and bass setup work for countless years and I do know how to adjust a truss rod. I was simply offering to pay for the repair based on the fact of it being a “used” bass, where “if” your build policy happened to change to include a warranty that it would only apply to the original owner, period. Let’s call it what it is and get all of the facts out there.....

 

[Rôckhewer]

Actually, what I amended the statement to, was that I backed the rod off approx 1/8” and then I went approx 1/4” (which technically was actually in two increments over approx 10 - 15 minutes) so it only turned an additional 1/8” over where it was when it seemed seized. What’s more, when I backed the truss rod off the sound of the friction between the wood and the rod was highly “audible” so I think it was seized. The measured string action at the 7th fret prior to making the adjustment was 2mm which was way to high for my hands with my medical issues.

Second, I make it a practice to always detune approx 1 whole step before adjusting the truss Rod and then retune after the adjustment.

Third, I offered to pay for the repair because this is a “used” bass that I purchased from another individual “and” you had told me in the past when I was placing my first order with you “that you do not offer any formal warranty on your basses”.

On top of being a mechanical engineer, I’ve been doing guitar and bass setup work for countless years and I do know how to adjust a truss rod. I was simply offering to pay for the repair based on the fact of it being a “used” bass, where “if” your build policy happened to change to include a warranty that it would only apply to the original owner, period. Let’s call it what it is and get all of the facts out there.....

I didn't have a formal warranty because I don't have the legalese knowledge to write such a thing.
But I implied I would "stand behind" any issues that might arise that were my fault.
This is why I posted about the issue here.
An attempt to analyze and get to the bottom of what happened.
To see if I was at fault...or the rod was faulty, or what....and make sure it never happens again.
...not to throw shade on you...Please forgive my skeptical tone. And "devils advocate" assumptions.

As far as I'm concerned... It's not a "used" bass that I won't stand behind. I built it.. and...
It's still "in the family".
And... at this point, (even without seeing it yet).
I would like to grant benefit of doubt... and would prefer to fix it free of charge.

 

[Slidlow]

I would like to grant benefit of doubt... and would prefer to fix it free of charge.

Way to go @Rôckhewer ! Sometimes the attempt to find out what really happened can be misconstrued though really most of us want to know what happened so we can work to avoid any occurrences in the future.

 

[Bruce Johnson]

A couple of things to think about:

It doesn't appear that this truss rod failed because it was defective or had a quality control problem. We've sometimes seen cheap truss rods fail where bad welds have broken. Nothing like that here. This rod broke with a straight torsional shear-off of the rod at its weakest point, right in the threads. That's its weakest link by inherent design.

The truss rod broke because the torque applied to the nut exceeded the torsional strength of the round steel rod.

All of the other brand truss rods of similar design that are being discussed here have the same weakest link spot: a 3/16" round steel rod with threads. And, they all have the same basic working geometry of the center spacing between rods, depth of slot, etc. By their design, they are going to apply the same amount of bending force to the neck for the same amount of torque applied to the nut.

So, why would any of those other rods be any stronger than this one was? Their 3/16" rods will all shear off at about the same amount of torque and load. A higher quality rod assembly with longer steel blocks, better welds, brazed joints, etc., doesn't increase the net strength. The 3/16" rod will still be the weakest link, the point that will break when that torque/load level is reached.

And, if you replace the truss rod in this neck with one of similar design, why wouldn't it break at the same torque/load level? Even if it's higher quality in design and construction?

To all of you who are arguing that this is why we should build our necks so that the truss rods can be easily replaced: If the original truss rod broke because it couldn't handle the load of flattening out the neck, what's going to happen when you pop in a replacement? It will break, like the original, at the same level of load, without flattening the neck.

That brings us back to the overall question of why did this truss rod get broken? We've heard from the owner, and it sounds like he didn't do anything malicious or crazy. He was trying to flatten out the neck by adjusting the truss rod, using the technique that he thought was correct. He didn't really do anything wrong. He just didn't have enough experience to recognize that the torque he was applying was approaching the breaking point of the rod.

The core of the problem here isn't that the truss rod broke, but that the neck failed by going out of range. The truss rod, by its inherent design, can only apply a limited amount of force. The neck curved far enough, and was stiff enough, that the force needed to pull it into spec was greater than the truss rod could apply. When he tried, it broke. But it's not the truss rod's fault. The neck caused the problem.

If a truss rod gets broken in a neck, that means that the whole neck has to be repaired, not just by replacing the truss rod. The neck needs to be brought into condition where it is close to the ideal shape, without help from the truss rod. Then the new truss rod can do its job; a small amount of adjustment to dial it in to the prefect setup. Fixing the neck may mean heat treatment to bend it straight, or resurfacing the fingerboard, replacing the fingerboard, whatever it takes.

When Kevin replaces the truss rod in this neck, he's also going to have to do something to correct the overall problem. Or, the new truss rod will just break too.

Okay, so how do you build new necks so that they don't ever end up with broken truss rods? You have to:

• Use good construction technique so that the neck doesn't warp over time, or move very much with the weather. Drying the wood properly, aligning the grain and rings, sealing it up, all that stuff.
• Don't build the neck too stiff. The stiffer you make the neck, the narrower the range in which the truss rod is able to help adjust it. If you must build the neck really stiff, then pre-shape the frets/fingerboard to the ideal shape and relief curve, to minimize the amount of work the truss rod has to do.
• Make the truss rod stronger in design. Improve the geometry to increase the leverage ratio, so that it can apply more bending force to the neck without exceeding the torque limit of the rod. Or, increase the diameter of the threaded rod. Give the truss rod enough power that it can correct a reasonable amount of neck movement.

I do all of those things in my necks. In 25 years of building, I haven't yet had any of my necks come back with a broken truss rod. But I've sure seen and repaired a lot of broken truss rods in necks built by others.

 

[rudy4444]

A couple of things to think about:

It doesn't appear that this truss rod failed because it was defective or had a quality control problem. We've sometimes seen cheap truss rods fail where bad welds have broken. Nothing like that here. This rod broke with a straight torsional shear-off of the rod at its weakest point, right in the threads. That's its weakest link by inherent design.

The truss rod broke because the torque applied to the nut exceeded the torsional strength of the round steel rod.

All of the other brand truss rods of similar design that are being discussed here have the same weakest link spot: a 3/16" round steel rod with threads. And, they all have the same basic working geometry of the center spacing between rods, depth of slot, etc. By their design, they are going to apply the same amount of bending force to the neck for the same amount of torque applied to the nut.

So, why would any of those other rods be any stronger than this one was? Their 3/16" rods will all shear off at about the same amount of torque and load. A higher quality rod assembly with longer steel blocks, better welds, brazed joints, etc., doesn't increase the net strength. The 3/16" rod will still be the weakest link, the point that will break when that torque/load level is reached.

And, if you replace the truss rod in this neck with one of similar design, why wouldn't it break at the same torque/load level? Even if it's higher quality in design and construction?

To all of you who are arguing that this is why we should build our necks so that the truss rods can be easily replaced: If the original truss rod broke because it couldn't handle the load of flattening out the neck, what's going to happen when you pop in a replacement? It will break, like the original, at the same level of load, without flattening the neck.

That brings us back to the overall question of why did this truss rod get broken? We've heard from the owner, and it sounds like he didn't do anything malicious or crazy. He was trying to flatten out the neck by adjusting the truss rod, using the technique that he thought was correct. He didn't really do anything wrong. He just didn't have enough experience to recognize that the torque he was applying was approaching the breaking point of the rod.

The core of the problem here isn't that the truss rod broke, but that the neck failed by going out of range. The truss rod, by its inherent design, can only apply a limited amount of force. The neck curved far enough, and was stiff enough, that the force needed to pull it into spec was greater than the truss rod could apply. When he tried, it broke. But it's not the truss rod's fault. The neck caused the problem.

If a truss rod gets broken in a neck, that means that the whole neck has to be repaired, not just by replacing the truss rod. The neck needs to be brought into condition where it is close to the ideal shape, without help from the truss rod. Then the new truss rod can do its job; a small amount of adjustment to dial it in to the prefect setup. Fixing the neck may mean heat treatment to bend it straight, or resurfacing the fingerboard, replacing the fingerboard, whatever it takes.

When Kevin replaces the truss rod in this neck, he's also going to have to do something to correct the overall problem. Or, the new truss rod will just break too.

Okay, so how do you build new necks so that they don't ever end up with broken truss rods? You have to:

• Use good construction technique so that the neck doesn't warp over time, or move very much with the weather. Drying the wood properly, aligning the grain and rings, sealing it up, all that stuff.
• Don't build the neck too stiff. The stiffer you make the neck, the narrower the range in which the truss rod is able to help adjust it. If you must build the neck really stiff, then pre-shape the frets/fingerboard to the ideal shape and relief curve, to minimize the amount of work the truss rod has to do.
• Make the truss rod stronger in design. Improve the geometry to increase the leverage ratio, so that it can apply more bending force to the neck without exceeding the torque limit of the rod. Or, increase the diameter of the threaded rod. Give the truss rod enough power that it can correct a reasonable amount of neck movement.

I do all of those things in my necks. In 25 years of building, I haven't yet had any of my necks come back with a broken truss rod. But I've sure seen and repaired a lot of broken truss rods in necks built by others.

Since I'm probably about 90% of "all of you" I'll simply answer that truss rods can, and DO break for a variety of reasons.

Sometimes it's a flaw in the rod itself and sometimes it's simple user error. I'm sure most here are aware of the large number of players who think that the truss rod is there to adjust string height. As Swift would say, "Misunderstanders gonna misunderstand".

Building to make a rod easily replaceable isn't about keeping a handful of rods close by to stick another in to try and correct a problem in the wrong way. It's simply to make life a lot easier for everyone when it does happen. When a rod breaks everyone feels bad and it's natural to assess "blame". That doesn't make it easy to fix; making the rod easily serviceable goes a LONG way towards that.

 

[Rôckhewer]

The neck caused the problem.

Ok hang on.... There's been a lot of "speculation" on this. I totally respect your opinions... and yes...
This could be a possibility, but I feel it's a fairly dramatic assumption based on the actual physical evidence.
... or lack thereof. (Just a pic of a sheared off nut)
I'd rather not speculate further here.
I have accepted responsibility.
And I will honestly share the actual condition of neck... (if it's bowed "out of range ").. or what. ...when I get my hands on it.
...In the spirit of education... (what not to do)
However, ... I am dumbfounded at the idea the neck got that far out of whack... just changing climate.
When the instrument left NY for Illinois... it was reportedly... "playing great, not sure why he had to crank on it at all" (quote).... according to a guy who likes his action slightly high.
I trust both these people.... they are my two best customers, and supporters.
I'll make this right...and let you all know what I see.

 

[Gilmourisgod]

I've never broken a rod, and I've always "helped" the rod by applying light pressure on the end of a 30" lever (the neck). I cant help but feel there may be some correlation between those two facts. The only neck I own (including the two I built) that doesnt easily bend with light pressure on the headstock (or in this case the string retainer) is my Steinberger, because the correct relief was cast into it, so no adjustment is possible or needed. Simply lessening the tension on the rod while adjusting it by loosening the strings and helping the neck seems like a no-brainer way to avoid reaching the shear torque of the rod. Since its possible to get DA rods that can be removed now, that also seems like a no brainer to plan for replacement. Stuff breaks, people screw up, necks unpredictably bend or twist, etc.

 

[Beej]

I have no doubt you'll get to the bottom and sort the instrument into wonderful playing condition again. Does your design mean the fingerboard has to be routed away? Just the thought makes me wanna hurl

 

[Slidlow]

Ok hang on.... There's been a lot of "speculation" on this. I'd rather not speculate further here. I am dumbfounded at the idea the neck got that far out of whack...

I'm with you on this one. I doubt your neck would have been the cause without some form of actual evidence. Any suggestion of such without seeing it seems a little premature and presumptuous.

 

[MPU]

My guess is that for some reason the truss rod thread on either end has seized. Maybe a bad thread or something in the threads. We'll see when the surgery has been done.

 

[mapleglo]

Subbed, because I have a million (ok, maybe 10) LMI truss rods in a few of my builds, and am curious about what Kevin finds.

Just looking at the sheared off nut and threads, it sure looks like there's a bunch of gunk on the threads. Maybe some kind of corrosion that seized up the threads. I have a hard time believing that the neck went wonky. I've seen a few of Kevin's builds with my own eyes, and they are top notch.

 

[deff]

Not going to speculate on the neck design in relation to the fracture, but there could be a million different reasons why the bolt snapped. There could be a hard inclusion nodule in the bolt, there does appear to be some corrosion there. That could have caused some depletion between interstitial grain boundaries. It could be straightforward ductile failure from overstress. If only someone here worked at a materials laboratory with experience in metallography.... ?

 

[Slidlow]

As a side note and further to the clearance around the truss rod nut I was working on this old Vantage bass. I always check and back off the truss rods before investing too much time and found this one tight. It came out but it was obvious there was a clearance issue. When I got it out I could see where the end of the nut has rubbed against the wood. The channel actually is not flat there and curves up to the headstock face. I will carefully remove some material before installing the nut again to prevent any future issue.