I laminated three pieces of maple and two of wenge to make up the neck, and ordered up a nice piece of ebony from LMI. I really liked the one-piece bidirectional truss rod that I'd gotten from Stewart-MacDonald that I'd used in my first bass, but they'd discontinued it. So I decided to make my own from 3/16" stainless steel rod and cold-rolled flat stock for the nuts. I was also intrigued by the strength of LMI's U-shaped carbon fiber bars and wound up with the sheer overkill of two truss rods and two U-channel CF bars in a thick-ish, hand-filling neck, with a thick ebony fingerboard on top.

This was my setup for routing the truss rod channels. Since they were blind routs, I couldn't do them on the router table. So I set up a straightedge on the bench and used it as a routing guide. The truss rods/CF bars splay along with the increasing neck width, for maximum stiffness. I figured those angles into the setup. Dust collection on the DeWalt 621 router, by the way, is superb. Hooked to the shop vac, you never see a chip.

Here's the neck after I bandsawed the taper. The CF U-bars are sitting in the neck routs and the stainless steel truss rods are sitting above them so I could lay out where the nuts would go and where I would need to notch the CF bars for them. 3/16 rod is handy because you can thread it 10-24 or 10-32--it's pretty close to the proper diameter. The hard part about making these truss rods was that I had to thread several inches of the lower part of the rod. Even with a brand-new die, threading stainless is a pain. The lower end got the right-hand thread, and the upper end, which only needed half an inch or so of threading, got the left-hand thread. Then I had to braze socket heads onto the end of each rod so that it would be accessible from the end of the neck. My guess was that once everything was glued up and I set some tension on the rods, that the pretty much wouldn't budge when I strung it up.  So I didn't bother making the adjustments accessible without removing the neck from the body. And that's pretty much how it went.

I put soda straws over the center sections of the rods to kill vibrations.

I also inserted a 1/8 by 3/8 inch CF bar into the headstock. Here I'm routing the slot for it on the milling machine, with the headstock clamped to the table. By going in the requisite 3/8 inch and just letting it come out under the fingerboard, the bar extended to the second fret. I glued it in with epoxy, and the headstock just plain doesn't flex. I would definitely do this again on any bass that I build, and might consider it for a guitar, too. I covered the bar with a veneer of wenge, so it would match the two wenge stripes in the neck. The only critical planning was having the reinforcement bar fit between the two truss rods.

I did most of the shaping on the neck with a Record spokeshave with a Hock blade in it. I've put some stuff in the MIMForum Library about how to set up a spokeshave--out of the box, it's a tool construction kit, not a usable tool. I adjust mine so that one side takes a heavy cut, the other a very light cut, with everything in between available across the blade. This neck went very quickly; I must be getting more confident.

Here's the neck with the CF rods being glued down. The nuts are visible just below the clamps closest to the headstock, right at the end of the black CF bars. The truss rods are under the CF, hopefully never to be seen again by anyone.

The headstock stiffener CF bar is visible in the center. I hadn't veneered it yet.

The completed neck is ready to be mated with the body. The neck has four knockdown-furniture barrel nuts just under the fingerboard. They go into the CF U-rods, but stop short of the truss rods. You can see the circular filler patches on the side of the neck.

I put four setscrews into the neck and leveled them, so that I could make accurate marks on the body for spotting the bolt holes. I used those flat-topped knockdown furniture bolts, which can exert a tremendous amount of clamping pressure.

If you look carefully in the above picture, you can see the hex sockets that are brazed onto the ends of the truss rods.