I was recently looking a 69 when I noticed the lower ball joint castle nut had not been tightened to the point where a cotter pin could be inserted. When I asked the owner what the problem was he did not seem to know. We put a wrench on it to tighten it up and all it did was spin but never gained any additional thread. The joint looks brand new and the threads do not appear stripped. Any one experience this or have any ideas short of replacing the ball joint.
Thanks,

If the ball joint has weight on it, the tapered stem should lock into the spindle. If it's not locked in there's a possibility that the ball joint may not be the correct one for the car. That is, the tapered angle may not be the same as the spindle

It's either the wrong ball joint or the spindle is so worn, it won't lock onto the taper anymore.

Got it.
Thank you all.

If it's got disc brakes from a mid 70's car (tall spindles) the lower ball joint will fit like that (too short and taper wrong). If you crank on the bolt, it will spin the joint, but can't tighten.

So, does it have 1 piece spindle-caliper bracket? Or does it have a 3 piece spindle-steering arm-caliper bracket?

Ask me how I know this. :(

Bill, are you going to the show in League City tomorrow?