Acoustic Guitar Construction

I've been looking around for a source for 2-way truss rods (seems to be commonly used) for my scratchbuilt project, for which I'm accumulating bits and pieces.

What's to avoid, and why? What's to be sought, and why?

I found what seems to be a valid source 'Bitterroot Guitars' peddling 2-way rods. From the looks of the picture the rod has a lengthy filleted weld between the rods, other' ads pictures show something lots closer to a tack weld at that position. Is this difference a determining factor? These rods say to use a 4mm hex key for adjustment, is that a routine size? Any other vendors' rods use larger hex bolts?

I'd like to install a truss rod only once. I'd very happily pay what needs to be paid for that peace of mind. Are there vendors who sell this peace of mind hardware?

And I'd also like to know what sort of preparation a truss rod needs when it's being installed, pre-lubrication of threads, for example.

Truss rods come in various lengths. Should I be purchasing truss rods whose length causes the threaded block to be clear of the neck, i.e., visible protruding out of the neck heel so as to be enclosed by the neck block when the neck is installed?

Thanks very much. If I'm asking redundant questions, I apologize. Tried to use the search tool and trying to get past the first page of search results gets me a not-authorized message from the software.

There's is no reason for a truss rods to extend into the body of the guitar.

The two-way welded rods do occasionally break (so does everything else, even on a well made guitar.

Here's the only two way rod I'd consider fail safe.

TRMR Truss rod, Martin ™ style, for steel string Yes $14.40 $12.80

LMII has them

Peter,
I used a 5 dollar brandless type (chinese or so), one from goldo (10 dollar) and several hotrods from stewmac (12 dollar).
The latter is the one I use now. It has brass endblocks, preventing corroding. There is no weld used.
I prefer the 4mm allen nut, because it needs the smallest rout.The hexnut is less worn-prone, but needs a big routing around it, for reaching it with a wrench. If you make the access from the soundhole-side it needs a (too) large hole in the upper brace.
The hotrod is quite powerful, a 90 degree turn does more then I ever needed.
2ct.
Herman

The first Hot Rod rod I used broke in the guitar the first time I tried to adjust it. The nut broke clean off.
That is the last one I'll buy. I like the LMI 2 way rod of their design, but it is pretty pricey at about $27 now.

I just put the LMII Martin style 2 way in the neck I'm completed and so far so good, I put some back bow in the neck to sand the fretboard flat so I'll have some relief after fretting, and it adjusted nicely. It is a bit long, but still works okay.

Kevin

I buy my rods from Bitterroot Guitars. No problems with them so far (about 11 rods, I have 4 more). I use 14 1/8" and buy the 5 pack.

Thanks, everybody. Much obliged. I'll stew a bit and buy something.

Just a side bar -- I cannot remember ever needing to add forward bow in a guitar to get the neck set correctly or setup adjusted -- no kidding!