I just got a bass that had a rounded out truss rod adjusting nut (bullet allen type). I got the allen nut off the rod and repaired it buy putting it in my lathe & turning off the hex part. I then ran a tap through it and cut down a allen screw just so there was a couple of threads left. I screwed it into the nut and tig welded it together, turned it smooth and polished it. When I screwed it back on the truss rod it felt like it was bottoming out on the rod. I then made some spacer shims on the lathe 3- .050 & 3-.100 thick. I put a .100 on the rod and brought the nut down. It felt good as I put some tension on it and let it sit for a hour. I checked the relief , it was .035 @ the 7th to 9th fret. I gave it another 1/3 turn and let it sit. When I checked the relief it was .030. I tried to give another turn on the nut and it felt like it was bottoming again so I took the nut off and put another .100 shim on the rod. I adjusted it up again and the same thing. .030 relief. It feels like the nut is bottoming out but it isn't. The nut is sticking out of the neck more then it was. There is .700 of threads in the nut and only .250-.300 of rod. When I try and tighten the nut and it feels like it is bottoming, I can feel the rod twisting if I put pressure on it. If I leave the nut off and tune the bass it has .035 relief so that tells me the truss rod is not doing anything. I back off on all the strings during the adjustments. I can't figure out what is happening.