Cartridge BB not threading in
 

I am swapping all the parts from my old bike to a different frame (a 2008). I have a Shimano XTR M952 cartridge BB. The drive side will only thread in about 1/4 way before it becomes very difficult even with the tool. I know the drive side is reverse threaded, and both frames have a 68mm shell. and english thread.
Does this mean I need to take the frame to the LBS to get the threads chased, or am I screwing up something obvious?

When you turn it in just a few turns is it really sloppy or is it already a precise fit?

If it goes easy and sloppy at first and tightens gradually that's a bad sign. Could be a lot of things.

If it goes in easily to a point and tightens over a turn or three that's just a sign that they threads need to be chased because there's a burr or similar in the threading or that the welding shrunk the BB shell a little or there's a small bit of welding distortion that will go away when chased.

did you clean the threads on BB and BB shell?

Have you tried cleaning the threads in the shell with a wire brush? Perhaps some debris is jamming the threads. Also, make sure you grease the threads.

It doesn't sound like you're doing anything wrong since you can engage 25% of the threads.

Thanks for the advice so far. I'll try and clean the threads out some more. It goes in easily about 1/4 way and then it just hits a point where it is really difficult. If I really crank on it, I can keep turning it, I just know that I shouldn't need to force it the rest of the way in like that.

It's possible to cross thread an aluminum cartridge bottom bracket in a steel shell. I learned that the hard way. The good news is that you probably haven't hurt the steel threads at all. Pull it out and maybe you can get it restarted. If the threads on the BB are too screwed up you may have to get another one.

I didn't think about the cartridge threads possibly being the problem. I should probably go ahead and try a new one anyway, I've seen these old M952 cartridges for as low as $20.

I definitely would not muscle it in there...proceed with caution.