Insufficient clearance in BB shell

I'm in the process of rebuilding my 30yr old Viscount Aerospace as a SS. I decided to upgrade the knackered stock cup & cone bearing bottom bracket to a modern sealed cartridge unit, BUT when I came to install the new unit I discovered the down tube, seat tube and chainstay ends protrude into the inside of the BB shell at the joints. Although there was plenty of clearance for the old BB axle, a cartridge won't fit.

I'm thinking that it's Dremel time - considering grinding off about 3mm of the protruding tube ends to clear the way.

Any thoughts? Anyone hit a similar snag? Am I about to terminally wound a piece of nice old British steel?

should be fine IMHO, just don't take anything out of the actual shell, keep it to the protruding tubes.

I can't see a problem with that. As long as you're really careful to get all the swarf out. Nothing fvcks up bearings and threads like that.

If it does not fit it may be you only option. seems like the frame builder may have been a bit sloppy with his mitering and / or sliped the down tube too far into the lug. IF you are not sure take it to a biek shop to have a look.

I thought viscount aersopaces used nasty proprietry BBs that were a PITA to get hold of?

i had that problem with an holdsworth. the inside of the BB shell made it look like a child had put it together!

bit of filing sorted it out no problems. like the other says, just be careful and take off as little as poss.

last time I had that problem, I chased the shell with my BB taps.

it won't be the last time.

you can get them for £30 odd (not a proper tool, just the right size and thread taps)

Cheers for the advice & encouragement... I'll give it a (careful) go.

fc9k: Have heard similar before - some had press fit cups in obscure sizes. Luckily I got a sensible one with a standard British BB.

edit

(duh)

damn! wish i found this sooner. ended up knackering my bb thread trying to file bits out for the same reason, thought id properly messed up. luckily the guys at harry perry recut my threads and fitted the new sealed casing for not much, plus we had a good laugh and a cup of tea.