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Progressing with my first acoustic build but I can't find a definitive answer to a question. I'm using a two way truss rod, so is it necessary to glue a fillet into the channel, or just fit the rod flush to the top of the neck and glue the fretboard?

I think you need to keep in mind that if the truss rod is loose in the channel, then it could rattle. This is why I prefer to clamp and glue a thin strip of wood on top of the truss rod channel. I then sand this flush with the rest of the neck before gluing the fingerboard on.

Trev

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http://www.PeakeGuitars.com

People do it both ways. Personally, I like to make the channel just a little deeper and glue in a piece of binding stock on top, then plane it flush to the neck. That way, I can be skimpy with the glue for the binding piece (so the glue doesn't muck up the truss rod), then liberal with the glue when gluing on the fretboard.

I just follow the manufacturer's instructions.

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Steve Smith
"Music is what feelings sound like"

Thanks guys. All valid points, but if you glue a fillet, isn't that the same as having the rod dead flush and then gluing the fretboard on? Obviously there is the point doncaparker made regarding gluing. I may clamp the fretboard on and see what rattles... or sleep on it or something.

The one I glued last night has no fillet (Allied two_way) but the channel was cut so there is no clearance at the top of the rod. It will not rattle. That let's me have maximun clearance under the bottom of the truss rod too.

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Steve Smith
"Music is what feelings sound like"

Another difference for me is that I don't have to chase the perfect channel depth, which is defined as being deep enough to fit the rod but not so deep that it allows rattling. I just route it a little deeper than needed for the rod, glue the binding strip on top of the truss rod,make sure both the rod and the binding strip are snug in the channel, then plane the binding strip flush. Perfect fit.

Don - about how much vertical clearance do you leave to fill in with the binding strip?

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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

About half the thickness of the binding strip. A typical binding strip is about the thickness of a side: 0.085". So, I make the truss rod channel about 0.04" to 0.05" deeper than the rod needs. Definitely less than 1/16", which is 0.0625". My point with the numbers is that this doesn't really need to put you in danger of not having enough wood behind the truss rod. 1/16" is not much, and this is less than 1/16".

Another nice thing about doing it this way: What if one end block on the truss rod is just slightly taller than the other? They should be the same, but what if they aren't? This way of doing it stops any rattling, because you are pushing down both the binding strip and the rod along the length during gluing, then later planing off the excess thickness of the binding strip.

All of this assumes you are using a binding strip the same width as the truss rod channel, of course. I use 1/4" for both. And you might need to round off one end of the binding strip, if your channel doesn't go all the way down the neck.

Thanks for the detailed answer, Don. That covers what I was wondering about. I like the idea of using a fillet but I haven't done it over concern about not having enough wood left to back up the channel near the nut, at least on thinner necks. The thinnest necks I've made are 0.800 at the first fret. Deduct 0.250 for the fretboard and 0.375 for the truss rod block and that leaves only about 0.175. If I used a 0.05 fillet, it would be down right close to 1/8" left.

I don't know what range of force a truss rod can exert under typical use and how that compares to the strength of 1/8" thick mahogany or maple. So I don't know if I should be concerned or not about going that thin.

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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

Well, you could make the fillet as thin as you want. Or just go without. I've done it both ways.