#1
Is there an easy way to tell if the truss rod nut is maxed out and more tension may strip or break the rod? It’s hard for me to tell because I have truss nuts that are very easy to turn but have an immediate effect on neck relief. I have some that turn very hard but small increments have immediate effect. And I have one (the one that concerns me now) that turns very hard, seems to be working, but requires more wrenching (tightening) than it seems like it should. It’s the Heritage which has a typical crowned hex nut in the headstock. The nut is brass, which may be intended to protect the rod because a softer nut material may strip before the steel threads on the rod strip. There is no broken or noticeably crushed wood under the nut- and the little steel plate insert that the nut tightens against looks good.

No portion of the rod end (threads) extends beyond the top side of the nut. Is this an indication that the threads are not maxed out? Since the rod threads are hidden, is there another way to tell? Could I put a thin steel washer under the nut as assurance (as a spacer) that I’m not tightening against bottomed-out rod threads? Is there any danger to removing the nut completely to install a washer as a spacer?

I just adjusted relief on this neck and it’s almost perfect now. I may even loosen to add a bit more relief after letting it sit for awhile, but just wanted to get some opinions before more wrenching.

Thanks
EBMM JP6, EBMM Bongo Bass 5-string, Heritage H140CM, ESP Tele Copy, ESP P-Bass Copy, ESP Maverick, Fender HM Strat, Ibanez ST-55, Epiphone Broadway, Taylor 310, Seagull S-12, Musicman Sixty-Five Reverb, Fender HRD, Ampeg B-25B
#3
Typically, when you adjust the truss, it's best to leave it alone for at least 24 hours. This allows the adjustment to settle in.

Even if you install a washer, you still run the risk of overtightening it and breaking the rod. If you snap the rod on a cheap guitar, it's game over. The cost of repair wouldn't be justified.

Also, you shouldn't be turning it any more than a 1/4 turn at a time. Let it sit for 24 hours, then repeat, if necessary. Out of the several guitars I own, I have some I've never had to adjust. On those I have adjusted, it hasn't taken more than a rotation to get the neck where it needed to be.

As Sstony mentioned, if you get it where you want it, leave it. You should know when you run out of threads, or it snaps.
#5
Most guitar makers recommend waiting 24 hours for the adjustment to take full effect. Otherwise, you end up chasing your tail. Will you likely see an immediate effect from giving it a turn? Yes. However, it's still best to wait.
#6
I would consider removing the nut, cleaning it and the rods threads and applying some lubrication. Paint or other foreign stuff may have gotten into the threads making it harder to turn. Or it may be maxed out.
Moving on.....
#7
OK thanks for the advice. I think I may be OK. However, in this case I think the difficulty in turning the nut is directly related to the high tension on the rod which must be very high. I use the same strings on my other guitars I'm comparing it to so I guess the tension (enough to do the job) varies a lot from one guitar to another. The lube idea is a good one.
EBMM JP6, EBMM Bongo Bass 5-string, Heritage H140CM, ESP Tele Copy, ESP P-Bass Copy, ESP Maverick, Fender HM Strat, Ibanez ST-55, Epiphone Broadway, Taylor 310, Seagull S-12, Musicman Sixty-Five Reverb, Fender HRD, Ampeg B-25B