It is a single action truss rod, that only pulls. The tension will tend to straighten the rod and to pull the neck backward. It is the reason why the truss rod is installed in a curved bottom slot.
My technique is to use two shaped rails to support the router sole, which thickness will follow the shape of the bottom of the slot. I cut the side on a single board, according to the plan.
And I split the board to get a couple of rails, that will be used to guide the router copy ring.
The rails are temporarily nailed on the neck wood.
Here we see the relief.
Making of the truss rod. A 4mm diameter stainless steel rod. Dieing on both ends.
A round piece of rod, 10 mm diameter. Tapped. Some thread locking glue to be safe.
Here, it is obviously not necessary, but I did the nut on the lathe.
The truss rod is hand shaped in order to follow the curve as on the plan.
The nut pocket. Using a little sanding cylinder on the Dremel.
A brass washer, cut to shape. Less friction between brass and steel.
The wooden cawl is traced using the rod curve.
A bit of metal varnish on that part which is not stainless.
The cawl is glued and planed flush.
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