MIMF

On the Allied rod, both screws are the same "handed-ness" (both RH), but are of different pitch. That is the whole trick.
Stanley used the same trick on block plane depth-of-cut adjustment screws. Works fantastic.

That looks like one of mine, too. But the threads on mine are quite obviously different on each end.

Chuck Tweedy wrote:On the Allied rod, both screws are the same "handed-ness" (both RH), but are of different pitch. That is the whole trick.
Stanley used the same trick on block plane depth-of-cut adjustment screws. Works fantastic.

Okay, so I guess mine isn't an Allied, maybe an LMI. They look very similar, but my threads are not like the Allied. Unless someone has a gram scale and a 14-1/4" Allied rod handy and you feel like weighing one, I'll check with Allied on a weight spec.

Thanks,

CB

Just for completeness, I have this calculation handy so I thought I'd share it:

Q:
If you have a 10-32tpi and 10-24tpi screw running the same direction, what is the equivalent screw pitch of the the "closing" motion of the two nuts (closing = the two nuts move closer together because the 24tpi nut moves faster than the 32tpi)

A:
The relative motion is:
1/24 [in/rev] - 1/32[in/rev] = 4/96[in/rev] - 3/96[in/rev] = 1/96[in/rev]

Therefore, the equivalent tread pitch is 96tpi
Not a practical thread to cut - even a micrometer works on only a 40tpi screw.

I have a 14.25" Allied rod. It weighs 118 grams or 4.2 oz. These are my favorite truss rods as well.

I just can't think of another decent double-acting rod that will be lighter than that.

The rod in question may be an earlier design. I know they went through a few changes to arrive at the present design.

Craig, that's an LMI rod. The Allied ones are similar, but rather than having right-hand threads at one end, and left-hand at the other, both ends are right-hand, but have a different pitch. This is called "differential screw adjustment", and provides finer adjustment and better mechanical advantage.
The Allied rods are hands down the best on the market.

Thanks guys! My LMI rod weighs the same as the Allied rod, but the votes are clearly in for the Allied rod. I'll give one a try.

CB

Mark Blanchard developed the differential thread truss rod, and used it for some years in his own guitars in a slightly different configuration before getting together with Allied. Allied gets them made in China.

Alan Carruth / Luthier

Okay, I ignored the wisdom of the forum and did not, again, use a truss rod. And again, I have a buzz when I play any chord that involves the 7th fret the D string and the 7th fret on the low E string. The buzz is coming from the string between the zero fret and the 7th. I can dampen this with my thumb and the buzz goes away. It is a sitar like buzz, so my guess is it is just kissing a fret. Neck is thick (1.060" average) and reinforced with graphite bars, so my guess is I am not getting enough relief.

So what would you do about it? Any way to identify which frets are causing the problem? BTW, fingerboard and frets are dead level unstrung and strings induce a little relief.

I'm considering dressing frets 1 through six under the low E string, putting a little more relief in, there only.

Craig

I fixed it, it was the 6th fret on the low E. I took to quick swipes with a fret crowning file, done.