At 10:43 PM 8/12/06 -0700, Mark Bulgier wrote:
>You tell us it is a BCA shell - any chance it is actually marked BCM?
>(Bocama?) Either way, it is probably formed out of sheet metal and
>welded. The vast majority of lugged BB shells were made this way in the
>period when your frame was made - cast shells were relatively rare. So
>what you're looking at is probably not a casting mark, but the weld.
>The weld is ground down to minimize its visibility, and of course tapped
>inside, but it is usually detectable both inside and out if you know
>what to look for. And sometimes it is downright obvious where it was
>welded, and it could definitely look like a crack.
A thought I had was that the mark across the threads was where the cutting edge of the tap had stopped. You see this all the time in female pipe threads because they're tapered and not run all the way through.
John Betmanis <johnb@oxford.net>
Woodstock, ON Canada