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I agree with this logic and don't use a filler strip. It's also how I was taught to do it by a very experienced builder. I glue the fretboard on in a way similar to what Freeman shows in his photo and it works fine.

Toonces - Could you please explain more how using a filler strip eliminates rattle with an LMI type truss rod? I don't see what the difference would be between the truss rod being up against the underside of a filler strip and being up against the underside of the fretboard.

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Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

I use the Martin double acting rod with no filler strip-it is bulletproof....

As I mentioned, it removes the slack in the middle of the truss-rod. After I install the filler strip, I plane the surface so that there is maybe 1/64" filler height at both ends of the truss-rod but there is probably about 1/16" left of the filler strip in the middle. Basically, the filler compresses the truss-rod down into it's slot. I also glue the filler with epoxy which means you get decent adhesion of the filler to the metal. Then the filler is glued to the bottom of the fretboard - no worrying about getting glue into the truss-rod slot while attaching the fretboard. You end up with a solid assembly that will not cause buzzing issues or perhaps cause unwanted tonal issues.

In my last post I wrote:
"I always glue the filler incompletely, but I make sure to wrap the rod with teflon tape (plumber's thread tape) so it doesn't get glued in."
That should be -
I always glue the filler in completely as in fully no sections without glue.

I had a neck I had glued up quite awhile ago that I wasn't happy with. The shaft was glued up from two pieces and it had a block added for the heel and peghead added. The two halves reflected differently and that bothered me. I decided to add a center stripe similar to what I suggested in this discussion.

The first thing I did was stack some saw blades together to match the width of the truss rod slot. You can use paper and thin cardboard spacers (washer style) to fine tune the thickness.
Then I found a piece of 1/4 inch scrap and after setting the fence cut it to that setting (don't move the fence after)
The next thing I did was align the edge of the scrap with the edge of the truss rod slot and hot melt it together making sure that the heel would go through the saw first.

After the hot melt hardens I raise the saw blade to the appropriate height, place a piece of scrap on the out board side to support the neck, hold the "jig" against the fence and begin the cut.
After I have finished the cut I turn off the saw and allow it to stop before removing the neck from the blade.
I use alcohol to loosen the neck from the hot melt glue.

Is the Martin stainless steel? Academic to me but just wondering. Seen enough rusty T/R's in my days.
Never glued the strip to the rod itself always to the sides of the channel, but clamped it in several places to push the rod down. Mr. the Cat is right, you can whack away on the neck and it's dead silent...

A fillet of wood can be added to the slot and sized to leave a truss rod slot or glued in full depth and a new slot cut. I had a scrap about the right thickness to demonstrate filling the slot, but I will probably use a veneer sandwich to add a little more interest to the stripe.

Clay, I was doing a mental game of how I would jig that up to cut the slot, pretty much what you did there. Establish a reference parallel to the slot that would ride on the fence, cut (or route) the channel starting at the heel and stopping at the nut, then gluing in the skunk stripe. Of course it is done for an entirely different reason on fender necks and is probably much easier with the sled over the neck blank.

Returning to the question of a filler strip or not, I think they were necessary on Martin style single acting rods (at least I used them on a couple of guitars that I built with that kind of rod). However with the LMII rods I have not for two reasons

First, the manufacturer says you don't. From their website " As the square stock bears against the bottom of the fingerboard, no filler strip is necessary"

Second, if I route a 3/8 deep by 1/4 wide slot the end blocks just fit tightly. In fact they have little bumps on the sides that lock them in place, almost like barbs on frets. I have to tap the rod into place with a hammer and block of wood. I always adjust the bar to its neutral position, once the neck is complete and strung up I tighten it as necessary to bring the relief to my goal. I have never had to introduce relief with a truss rod, I know it will do that, but its always a matter of taking some out. That brings the bar snug against the f/b - there is no way its going to rattle.

I don't think the filler hurts, I just don't see a reason for it.

Your description of compressing the truss rod down into the slot with the filler strip makes sense, so I get that now. I would point out though that on the LMI rods I've had (not Hot Rods) the flat surface of the rod that goes against the underside of the fretboard (in my necks) is slightly convex up in the neutral position. So with the rod installed in the slot with the ends of the rod flush with the upper neck surface, installing the fretboard pushes the middle of the truss rod down. Maybe not as much as your approach does though.

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Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

Of the ones we have taken apart to make up Size 5 rods, the steel is oxide coated, then an anti-corrosion compound is applied to the rod prior to a full length heat-shrink sleeve. We have not seen or heard of a Martin 2-way rod that showed any issues (e.g., rattle, excessive wear or force required to adjust, corrosion, or failure) but there are only a million or so in service, and just since 2005, so early days yet.

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For the times they are a changin'

- Bob Dylan

I've had a Hot Rod blowout just like that. The Hot Rod is just too tall and limits the amount of wood you have under the channel. Fix the blow out using the gouge method recommended above then put a fillet of some strong wood like maple in the bottom of the channel so you can use a shallower rod. An Allied or Blanchard rod will work. Get the end of it into the deeper wood just past the nut slot if you can then just follow the install instructions with the rod. The repair I did has held well for 10 years.

I had the piece that came out so I glued it back in


Big difference in height between the Hot Rod and Allied/Blanchard style rod. I put graphite rods in two guitar necks, this one has an adjustable neck joint so the graphite rods where mostly there to support the fretboard extension (won't do that again, didn't support it very well). Haven't used the graphite rods since.


Besides adding a maple fillet to the bottom of the truss rod slot I was able to seat the Allied rod further in the neck so there was more wood under it.


After all that I finished the truss rod install normally.


Then put the fretboard back on, refretted it and refinished that part of the neck.

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Steve Smith
"Music is what feelings sound like"

Excellent repair work Steve,
It's nice when it all goes back together so perfectly. When you have the matching piece of wood it helps a lot. There are a lot of products out there to help blend in less than perfect repairs but most people aren't familiar with them and it does take some practice to become proficient using them.
But that one not even the hairdresser would know.

Thanks Clay. If you know its there, you can see it but doubt anyone would notice it otherwise.

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Steve Smith
"Music is what feelings sound like"

Let me ask this question.
What is the optimal thickness between the truss rod and the outside of the neck.


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In other words how much wood do I need between the rod and the outside world ?


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About 3/16".

Looking at my templates for the neck shape that I like, at the nut the total depth of the neck and fretboard is 7/8. If the f/b is 1/4 that means the neck is 5/8. If the truss rod slot is 3/8 deep per the manufacturer, then I have 1/4 inch off wood between the slot and my thumb. I'm happy with that.

Gibson style necks with the adjuster at the head might end up slightly thinner, but not much.

I use a single action rod but have it adjust at the heel end. I cut the slot with a 6" dado blade and the channel ends at the first fret following the curve of the blade. This puts a bend in the rod and the anchor right under the fingerboard so I probably have 1/2 an inch of wood under the peghead end (where the force is pulling the rod "down") and 1/2 inch of wood -above - the rod along the length of the neck (where the force is pushing the rod "up"). No blow outs so far.

In the book we recommend at least 4mm, with the bottom of the channel rounded (cut with a round ended end mill). No problems on many, many guitars.

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au