I swapped in a new stock on my Norinco SKS. I found the old cross bolt had an almost stripped out threaded end and the nut was damaged as well. (The old stock had a couple long horizontal cracks at the cross bolt area. Much damage was done by prior owner.)
I cleaned mine and installed it with JB Weld so the nut can't separate from the bolt. But the rifle is now so nice that I'd prefer to find a good cross bolt and nut to bring it back to 100% condition mechanically. If you have one for sale, please PM me with price. Thanks!