Truss Rod Questions #4,372, #4,373 and #4,374

[antipodean]

My '00 thick neck 4001 V63 had a bit of relief, so I took off the TRC for the first time to do some tweaking and found the following:

- The treble side had about 3mm of thread protruding from above the nut;
- The bass side had none;
- The metal plate that the nuts sit against was at a slight skew (about 1.5-2 mm from true i.e the treble side was 1.5-2mm lower than the bass side).

After a pause for thought, and keeping the bass tuned to pitch, I loosened the treble side nut to the point where there was no tension - there was still 1.5-2mm of thread protruding, then tightened it back to where it was just offering resisitance and tightened the bass side by about 1/4 turn (normal resistance to the turn) and waited a day.

The neck didn't appear to adjust, so I adjusted the bass side a little again (bending the neck flat as I did so). After about half a day I noticed that there was a little less relief (on both sides of the neck!) and it appeared that the plate skew had reduced. I repeated the process a couple of times (with appropriate waiting periods), and the relief has diminished again very slightly, and the plate skew has been reduced a little further. There is now about 1 mm of thread protruding above the bass side nut.

My questions are:

- Is the glacial pace of the change in relief normal? Could it be that the thick neck requires more truss rod adjustment to achieve a given change in relief than a thinner neck?

- Is the difference in the amount of adjustment on the two rods an issue?

- Is the skew on the metal plate symptomatic of a darker problem, or am I just being paranoid?

I know a pic would help - but the camera has gone walkabout again... I'll see if I can conjour one up...

Thanks in advance for any advice you can offer!

[jingle_jangle]

First off, Evan, it's likely that your bass was treated to the efforts of an impatient and only semi-competent setup by a repair person or previous owner.

Necks vary in adjustability, and also in speed of response, depending on a number of factors, of which hardness of the wood, what kind of strings have been fitted, and cross-sectional area of the neck are a few. Time is definitely a factor, and we're used to seeing immediate results everytime we turn a wrench or screwdriver on our car or home project, so why not a bass?

But, in reality, this is a system of organic and mechanical components which needs only tiny tweaks to maintain balance, and which reacts very slowly and stabilizes even more slowly.

I'm glad that you took the prudent approach, and can find nothing to fault in your analysis and handling of the situation. (Jeez...I'm beginning to sound like Miss Manners here... )

On to your questions: You have done a lot of good and staved off what could have been a serious situation sometime in the future, by simply letting things rest under less tension and then slowly bringing the tension of the rods back. Theoretically, the plate should remain square to the slot; if it's cocked badly, there's a potential issue involving too much tension and possibly softer wood on that side of the neck. There's been mention by JH of a fix which uses water-thin super glue applied in drops to softer end-grain and allowed to cure, in order to reinforce the wood's cellular structure in that area, preventing the plate from "digging in". The old, labor-intensive, handmade aluminum blocks were superior to the plates in this respect: they distributed the load on both truss rods over the entire pressure area and did not "dig in" due to their thickness and the rounded corners. But the simple expedient of super glue in the end grain goes a long way toward correcting this.

The thickness of the neck should not be a factor in tensioning the rods, because the rods counteract the tension of the strings, and the neck is a compression member in the equation. However, the thickness does affect settling-in time.

The difference in adjustment amount should not be too great between the two rods.

Sounds like you've got the skew problem handled; if not, use the super glue trick and reassemble and readjust.

You're doing everything right so far.

[antipodean]

Thanks Paul!!

[jingle_jangle]

Woof!!!

[johnallg]

- The treble side had about 3mm of thread protruding from above the nut;

After a pause for thought, and keeping the bass tuned to pitch, I loosened the treble side nut to the point where there was no tension - there was still 1.5-2mm of thread protruding,

As to #4,373 question, it sounds like the nut at the headstock end is not moving, but the rod is moving at the acorn-nut end. I also suggest looking for soft wood on the treble side.