bb advice please

[wobblyknees]

Hi, I am currently restoring a 1957 Holdsworth "Monsoon" and have encountered an unexpected problem. My Campagnolo bb cups (1.370" x 24 TPI ) don't appear to thread on by hand as easily as I anticipated and I am unwilling to use any pressure for risk of damaging the 68mm shell thread which looks ok at the moment. I have been unable to establish the shell thread spec. to date. Any advice would be most welcome.
Cheers!

 

[biggs682]

Silly question time . Are trying to screw the correct cup in to correct side ?

 

[rogerzilla]

It'll be BSC thread. Chances are that it just needs a BB tapping set run through it. The true outside diameter of BB cups varies a lot and can be nearer 1.360". You just have a tight set.