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Repairing a broken
Removable Truss Rod
© Frank Ford, 7/21/02; Photos by FF

It's a classic. A 1960s Harmony Sovereign - just about the best deal for the money in a dreadnought size guitar at the time. Soon, of course, Harmony was blasted out of existence by the likes of Yamaha and others who made copies of Martin guitars. But, that's another story.
The story here is a broken truss rod, and it's also a classic. The rod had rusted enough that the threads were binding in the nut, so when it was tightened, the rod itself twisted and broke. Chances are that this rod would not have broken if the nut had been removed rather than tightened. Then, of course, the treads could have been lubricated to avoid such binding friction.
Clearly, my first course of action was to excavate and remove the washer you can see in the previous photo. I cut around it with my X-Acto knife. It took a lot of picking, but I was able to excavate enough to get the washer loose. Even though I'm not a big fan of these replaceable blade knives, I do use them frequently when it seems likely that I'd damage the blade of a good knife.
After removing the washer, I was able to grip the end of the truss rod with my needle nose locking pliers. I'd rather have used a threaded rod and simply screwed it onto the end of the truss rod, but the threads were pretty messed up when the rod twisted and broke.
Once the rod was out, I could "chase" the threads with a regular 8-32 die, and could even add a few extra threads down the rod. Standard, nonremovable truss rods can break in this same way. Here's a possible fix for that kind.
Let's look more closely at the rod itself. Here's the broken end, and you can see that the washer is really much more than just a flat washer. It's a collar that couples both the free ends of the rod. This is how the assembled rod looked right after extraction.
The end near the body is "fixed" by a inch long weld that couples the two rod sections. Some of these double rods are actually a single rod that's simply folded in half.
Using my little 1" x 42"belt sander, I shortened the unbroken free end of the rod by the same amount that had been broken off before. I estimated it because the adjusting nut was long gone, and I would have to supply my own new one.
The shortened end fit right up into the adjusting collar.
I made a new 8-32 nut from a 1/4" long piece of 1/4" brass stock. An ordinary nut would have worked, but the brass nut would be unlikely to strip the steel threads, and the extra length gave me lots of threads to grip. That's the reasoning behind most truss rod nuts.
In this photo you can see how the collar captures the upper end of the rod, pressing on it as the nut is tightened. Tightening the nut stretches and lengthens the lower rod while compressing the upper. Then, as the rod bends, the neck bends slightly, too. Straightening it against the string tension.
And, before installing any truss rod, I add some precious lubrication. In this case, it's white lithium grease. With any luck the lubrication will prevent future breaks.
With the rod back in place, all's well again.
My regular truss rod wrench works on the nut, and the rod acts normally, straightening the neck without me having to apply undue force.

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