Official Luthiers Forum!

I imagine many of you received the recent email newsletter from Stew-Mac with a link to a video demonstrating a jig that allows a table saw to create a curved truss rod channel. While I applaud the ingenuity, I'm left wondering how I missed any past references to the need for such a procedure. Is this just for repairing old Gibsons? More to the point, are you putting a curve in your truss rod slots? If so, why?

Here's a link to the demonstration: https://youtu.be/9Okx5YLePPs

Curious,

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George :-)

I saw that too and wondered the same. I took it as this method was to restore an old Gibson because it was a single action truss rod with the back bow created by the curved slot being the other action? Hopefully someone else chimes in as I was curious as to why one would do this as well.

A single action truss rod is like a giant string. When you put tension on it, it tries to pull into a straight line, and likes to vibrate and rattle against the walls of the channel. If the channel is curved, then when the rod tries to pull into a straight line, it pulls against the convex wall of the channel and isn't able to vibrate.

Must be for single action rods. On a double action maybe a sloped channel if you adjust thru the soundhole And you want the nut further from the soundboard, but Can't using a curved channel for double action

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Joe Beaver
Maker of Sawdust

I use single action rods in a curved channel. Nice and light. The curve sort of concentrates the relief adjustment to the nut end of the rod where it is most beneficial.

Interesting. I've always used two-way truss rods. Good to know that I'll need to look into a different approach for cutting the channel, should I ever decide to use a single action rod.

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George :-)

Gibson and Bennedetto do (did?) it this way.

It is simple, effective and the lightest of the adjustable rods....

I use this type on my archtops

not all truss rods work on the same principal. You have 2 different methods of controlling neck relief
A flixible truss rods
Martin , uses this style and all 2 way rods do this. The neck is flexed by a mechanical means not tension

Note:
As you adjust the rod the rod flexes and pushes on the neck one way or the other. So in a way this is a mechanical rod

B compressible rods
Gibson used this as did other manufactures. A simple long threaded rod with a fixed end on one end. A fixed point at the adjuster end. As you tightened the rod the neck flexes under tension. To make this a 2 way rod you simply adjust tension on the neck flatten it then glue on the fretboard. This allows you forward and backward adjustment.
Wayne Henderson uses this method but his barrel nut is inside the guitar.
Gibson has the ugly head stock cover on the head plate

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it