Seating an LMI dbl-action truss rod effectively

[Basschair]

Hello all,

On a current project, I decided I wanted to try orienting the truss rod with the adjustment nut on the body-end of the neck (set neck, though I doubt it matters in this case). At any rate, I was planning on routing a channel with a square bottom to seat the two rod-holding ends, and a round bottom under the rod itself (snugger fit to prevent rattle), perhaps with a touch of caulking in a few spots.

In other projects, seating the rod so that the square portion is absolutely flush with the neck's front surface and using a drop of caulking under the blocks was sufficient enough to keep the rod in place once the fingerboard is glued down. Is this the case with a body-end adjustment orientation as well? Should there be a small fillet over the adjustment nut (between the nut and the fingerboard?

At any rate, mainly looking for comments, suggestions, etc. from your experiences. Thanks...

[wilser]

Just wondering ...why do you want to do this? This truss rod was designed to sit in a square 1/4" wide x 3/8" deep slot. I caulk all the length and the threaded ends and this has worked fine for me and many others. Please explain your reasoning behind this?

If it's because you want it to fit snug, a truss rod is supposed to be snug when in tension, it should move freely so adjustment is not restricted.

[Basschair]

Originally Posted by wilser

Just wondering ...why do you want to do this? This truss rod was designed to sit in a square 1/4" wide x 3/8" deep slot. I caulk all the length and the threaded ends and this has worked fine for me and many others. Please explain your reasoning behind this?

If it's because you want it to fit snug, a truss rod is supposed to be snug when in tension, it should move freely so adjustment is not restricted.

You caulk the whole length of the channel, huh? I remember reading (probably here) that it's a good idea to protect the threaded portions at all costs. I guess I should revise my approach

What I was thinking was that the round area under the rod will discourage any sliding of the rod (in theory, at least) along the axis of the neck. The square ends will seat in the square-bottomed sections of the channel, and would not be able to slide into the section with the round-bottom. Of course, if the truss rod is snug enough, it shouldn't slide anyway...it would really be another line of defense against unwanted movement.

Do you think the round-bottomed portion of the channel would interfere with the truss rod's operation?

[wilser]

I think the additional friction is an unwanted side effect. Really, this is not necessary. I don't want to sound like I'm trying to discourage you from experimentation, 'cause I'm not, but experimentation should try to resolve a problem, which in this case just isn't there. Maybe I'm just not understanding what you're trying to achieve?

Also, the small fillet you're asking about above the adjusting nut, you can do that for asthetics, but it won't have any functional effect on the truss rod's operation.

[Basschair]

Ultimately, what I'm trying to do is just to make sure that the entire truss rod itself stays where it's supposed to rather then to slide within the channel. I know it won't slide out of the channel altogether (that would be a sign it's time for me to take up another hobby ). I just want to make sure it's absolutely secure. It does sound like precedence should rule on this one, and a standard square-bottom channel should be used, along with more caulking than I was using.

Wilser, would/do you use a 1/4" x 3/8" channel ALL the way through the channel, including under the threaded portion of the adj. nut, and then widen/lengthen it a bit to make room to get the allen wrench in?

[wilser]

I use a 3/8" deep by 1/4" wide channel all through the length of the rod and out the way the adjustment nut will go (either body or headstock). Then I use a 1/2" round bottom bit in the same router setup (to assure it'll be on the same center line) and route a little deeper (only until the square bottom is not visible) ONLY up to where the adjustment nut ends when the rod is straight. But all my earlier basses used a straight 1/4" x 3/8" channel all the way and out where the adjustment will be and no problems have been encountered with this method. The round bottom thing now I do strictly for asthetics, no functional gain at all.

If you look at one of these installed rods, there is enough room from the 1/4" x 3/8" channel for the nut to adjust freely (it doesn't touch either wall or bottom).

[Basschair]

Originally Posted by wilser

I use a 3/8" deep by 1/4" wide channel all through the length of the rod and out the way the adjustment nut will go (either body or headstock). Then I use a 1/2" round bottom bit in the same router setup (to assure it'll be on the same center line) and route a little deeper (only until the square bottom is not visible) ONLY up to where the adjustment nut ends when the rod is straight. But all my earlier basses used a straight 1/4" x 3/8" channel all the way and out where the adjustment will be and no problems have been encountered with this method. The round bottom thing now I do strictly for asthetics, no functional gain at all.

If you look at one of these installed rods, there is enough room from the 1/4" x 3/8" channel for the nut to adjust freely (it doesn't touch either wall or bottom).

I gotcha: for aesthetic reasons, you round out the bottom of the channel under the adjustment nut (about 1" of the channel). For body-end, does your adj. nut come to just under the end of the fingerboard, or is it back a little further?

[wilser]

My necks usually go all the way up to the neck pickup, so I use the round part from the end of the fingerboard all the way down till the neck ends.

[Basschair]

Originally Posted by wilser

My necks usually go all the way up to the neck pickup, so I use the round part from the end of the fingerboard all the way down till the neck ends.

No kidding? I've looked over your set net pictorial quite a few times, and was going to do the same thing (extending the neck wood up to the neck pup). So you extend the round bottomed channel all the way to the pup pocked?

[DSB]

Just thought Id chime in...

All the instruments I make have a half round truss rod channel (3/8" deep x 1/4" wide) the entire length under the truss rod. The rods I use are similar to LMI except the square threaded portion on each end is shaped half round (convex) to conform perfectly to the truss rod channel.

This delivers a stronger stiffer neck (since I am removing less word) which is obviously desireable with a bass. I can assure you that there is NO extra friction and all my necks adjust smoothly.

[Basschair]

Hi DSB,

Any caulking or anything else to prevent rattle?

Originally Posted by DSB

Just thought Id chime in...

All the instruments I make have a half round truss rod channel (3/8" deep x 1/4" wide) the entire length under the truss rod. The rods I use are similar to LMI except the square threaded portion on each end is shaped half round (convex) to conform perfectly to the truss rod channel.

This delivers a stronger stiffer neck (since I am removing less word) which is obviously desireable with a bass. I can assure you that there is NO extra friction and all my necks adjust smoothly.

[DSB]

Originally Posted by Basschair

Hi DSB,

Any caulking or anything else to prevent rattle?

No need to, once there is any tension whatsoever on the rod there can be no rattles. I can see maybe getting a tiny rattle if the rod was perfectly nuetral, but just turn it a tiny bit, and I mean a tiny ammount - not enough to change relief, and there can be no rattles.

I've been doing this since day one and have never encountered a problem.

[Basschair]

Sweet: I'll have to give it some consideration.

Originally Posted by DSB

No need to, once there is any tension whatsoever on the rod there can be no rattles. I can see maybe getting a tiny rattle if the rod was perfectly nuetral, but just turn it a tiny bit, and I mean a tiny ammount - not enough to change relief, and there can be no rattles.

I've been doing this since day one and have never encountered a problem.

[Linas]

I just routed my truss rod channel and i have some questions. I am using a LMI double action so i thought i would contribute to this thread. First off, what kind of caulk should i use, and how thick? Second, the non adjustment end is a little wider than 1/4", should i just hammer it down with a block? Third, since its going to be tight in there, do i need to glue it in?

[Cliff Bordwell]

Originally Posted by Linas

I just routed my truss rod channel and i have some questions. I am using a LMI double action so i thought i would contribute to this thread. First off, what kind of caulk should i use, and how thick? Second, the non adjustment end is a little wider than 1/4", should i just hammer it down with a block? Third, since its going to be tight in there, do i need to glue it in?

You need to grind the weld bumps down so the rod slides in easily. Don't glue it in just use a good clear silicone caulk in the bottom(about every 1.5") of the 1/4 ballnose channel. Square up the bottom of the channel were the welded block will sit.

[Linas]

Im just using a square channel. I heard its ok with this rod and i dont really feel like spending the extra $ for the bit. None of my channel will be showing so aesthetics is not a problem here.

[jongor]

Drudging up an old thread....

Just so I'm clear, the LMI dbl-action truss rod goes in with the flat bar on the top like in DSB's pic?

[Musiclogic]

Many of us have different techniques. I think they all have validity. I have done both square bottom and round bottom channels, and have found very little difference between the two. I think you should go with whatever process makes you feel most comfortable.

If you have a 1/4" cove bit(Round) you can cut the channel to depth, and then square up the ends for the blocks. It's really a simple process.

[jongor]

My question is which way does the truss rod go in, not how the channel is routed.

Does it go in like in the pic, or with the flat bar on the bottom?

[Phil Mailloux]

Yes, it does go in like the pic.