www.KitGuitarsForum.com

I have built up the mahogany necks for my two OM guitars with 12 fret short scale necks, and bought double action truss rods. They are Canadian made but essentially identical to the type sold by LMI. I have done lots of research but am still confused as to where the truss rod should sit at the body end. I will be using (for a number of reasons) the mortise-and-tenon-barrel-bolt method used by many, and well described on Cumpiano's web site. His drawing shows the threaded nut sitting on the headblock. I've also found the O'Brien youtube video very helpful, but if I understand him correctly, he says the nut should NOT sit on the headblock but on the tenon. What's the "best practise"? Second question - if these truss rods, which are the shallow, flat-bar-on-top type, are installed as intended, it looks as if I will have to cut clearance through the flat brace aft of the headblock (or slot the top of the guitar.) Or can I set the truss rods deeper and glue in a spline on top?

I take it you're setting it up to adjust through the sound hole. I didn't worry about the exact location of the nut --- maybe I shoudl have. I set it up so the nut was just flush or slightly recessed in the head block. I modified an Allen wrench for adjustment so I wouldn't have to cut a hole through the brace. Just clamp the wrench in a vise and heat with a propane torch until it's red hot, at which point it bends easily.

I like the end of the truss rod to be just out of the block for easier access

tippie53 wrote:I like the end of the truss rod to be just out of the block for easier access

Me, too ... and by "just outside" I like it to be no more than an eight of an inch (3 mm) or so.

Thanks for these replies - I'm getting closer. By the "end " of the truss rod, do you mean the metal block through which the rod is threaded, or the actual end of the whole mechanism, which has the hex socket in it for adjustment?

I just want about 1/4 of the end of the mechanism exposed so I don't have to fight my way into the neck block.

Thanks for the clarification, John. I now realize that the truss rods I bought listed "for 12 fret guitars" are in fact too long at 14", so I have ordered 12 fret Hot Rod truss rods from Stew Mac. Ah me . . . While I wait I will set up for cutting the neck joint mortises (tenons are done.)