Official Luthiers Forum!

John: Don't have much faith in straight compression rods. However a single rod bent into a bow high at head stock and high at the body and low in the center of the neck with a wood insert on top of rod is an excellent design and puts more desirable stresses on the neck. Think Gibson may have used this at one time. Just my opinion of course.
Tom

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A person who has never made a mistake has never made anything!!!

Double Action compression rods. Stainless Steel and lightweight, no blow outs

Tim L, I don't want to highjack the thread but I have been thinking of drilling my surface plate for a vacuum line for a long time. Did you drill those yourself?

Tim: Nice looking rods. The one problem with compression rods in my mind is the very fact they compress....!! There have been necks that developed an "S" shape due to the length wise compression. Single bent rods want to straight out when tightened and don't cause the "S" shape to form. Not that it happens all the time with the straight compression rods but it can happen.
Tom

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A person who has never made a mistake has never made anything!!!

I like single action rods. I never have had a need for dual action on the guitars or necks I have made. On necks with an adjustable rod, I make every effort to have a dead straight neck with the frets installed and no string tension. That way, I always end up with a bit of tension on the rod to counteract the string pull.

Nearly all the simple compression rods I have used have been that design (concave up). The aluminum channel rods (Martin, Gotoh) work on the same principle. A variation on the aluminum channel is where the channel is made of carbon fiber or a hard wood like black locust. Using a channel helps eliminate the problem of the simple rod's anchor burying in the soft mahogany.
I don't do many adjustable rods on the guitars I am building these days. I use a steel tee bar, or simple carbon fiber reinforcement.

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John

David, the surface plate is on a CMM. I did not drill or put the inserts into the granite. That is the way it came from the factory.

Tom the rods are put in deep into the neck. The size of the anchors determines that depth. Neck with fretted fingerboard are dead flat and the rod is slack before stringing, there is no pre load. Slot for the rod is to size and then back filled with a mahogany strip. i think that if there was any problem with an S shape the people who use these rods would have certainly said something by now. Traugott and Claxton have been using these rods for years as well as SCGC. SC switched to bending type rods but after repeated blow outs switched back to these.
They don't have a lot of range, but if your neck is seasoned and flat you don't need much. Once again there is no need for pre loading.