Originally Posted by onespeedbiker

First a couple of clarifications; you show the non-drive cup partially threaded, so I assume your threading issue is with this cup. Do you any trouble threading in the drive side cartridge? I'm betting the non-drive side threaded cup has some cross threading (as it is the only part of the BB/shell that is aluminum). In order to track down the problem, you should try threading the fixed side cartridge into the non-drive side (assuming it threads in the drive side without a problem); my guess is it will thread in no problem, which points to the non drive threaded cup as the problem (you may be able to thread the cartridge all the way through from one side to the other as Italian BB shells are often cut this way; regardless, there is certainly no reason to chase the shell threads if the BB threads in easily on both sides). If this is the case, check the threads on the non drive threaded cup; again I'm guessing there is crossing threading at the beginning (it may be hard to see). The problem with using the driveside lock ring to clean up the threads on the cup, is the ring will most likely follow the cross threading, but it will work on the cartridge threads. Below is a method to fix the problem if it's the non drive threaded cup, however it uses the BB shell to fix the cross threading. It would be better to either try and purchase a new non drive threaded cup or use a lesser bike to clean up the cup's threading.

The way I have solved this is to carefully thread non drive threaded cup in the shell, if the cup is cross threaded, it will not thread in evenly and instead cant to one side as it picks up the cross threading; there will be a high side and a low side. Loosen the ring slightly, and give it a tap to the high side with a hammer so the ring is square with the shell. Continue threading in the cup and if the ring starts to cant again, realign the ring with another tap; repeat until the ring threads in square (it is unlikely the cross threading is beyond the first couple of threads). You will probably have to use a tool for threading, but the amount of force will not be much; if the force ramps up at all, stop and evaluate.