Bicycle Mechanics - Really tight bottom bracket

I have changed over my bottom bracket from a cup/cone style to octalink on my '92 RB-1 (english thread, 68mm). The right side went in with no problem, but the left side adaptor was extremely tight. The first few turns were fine, then it became difficult. I stopped trying to get it in all the way. Provided that I have not cross-threaded it (doesn't seem to be and the first few turns were OK), is it probable that the cup/cone just used fewer threads and that the others further inside the frame were just dirty / paint overspray? I coated all the threads with grease. Thanks.

Sometimes this happens. You can try backing out the cartridge and torquing the NDS cup first, then tightening the cartridge. Also some grease on the NDS cup / cartridge interface might help (and might forestall future creaking). If none of this works, it's okay to have a little of the NDS cup protruding.

Oh wait, is Octalink like a cartridge, or is it external bearing? I'm assuming from your description that it's cartridge. I still have all square taper, so no experience.

be sure that the screw that holds the cable guide under the BB doesn't interfere with the cartridge threading inside the BB.

I found the problem. There was a metal shaving in the first thread of the bottom bracket shell. Because the adaptor tapers slightly in diameter (narrower at the beginning and getting wider towards the end), the first few turns didn't rub tightly against this shaving. But, as the adaptor was screwed in more, the diameter grew and rubbed more on the shaving making it tighter. Once the shaving was removed, it screwed right in.