Cutting down cartridge bottom bracket left cup I have a Tange 68x103 mm bottom bracket (pictured) that I plan to use in an old steel frame (building a single-speed/fixed). It turns out that my non-drive-side bottom bracket shell threads were a bit destroyed. My LBS was able to chase/tap quite a bit of it, perhaps enough to fit Hollowtech-style BB cups that they likely tested with afterwards.

However, the Tange BB has a very long left cup and it does not fully fit into my BB shell. I would like to somehow shorten it. Given that the BB cup has no lip on it, I plan to insert it in reverse on the non-drive-side, and then somehow cut it down to size, likely with a hacksaw. Is this a crazy idea? Does anyone have tips on ensuring the threads are preserved?

I'll likely cut off 6 threads or 1/4". From my point of view, the function of the cup would be preserved if I can successfully do this. Am I wrong?

Tange 68x103 BB http://www.benscycle.net/bmz_cache/a/a1a0837709b9deb5702d1c46199e4f77.image.700x524.jpg
Another alternative would be to find a LBS with access to "Sutherland's Handbook for Bicycle Mechanics" and find a BB with the appropriate measurements. Much easier, and quite possibly cheaper in the long run.