Hi all. I recently bought a new Guerciotti frameset (cast lugged etc.) with an Italian threaded bottom bracket (http://www.planet-x-bikes.co.uk/i/q/...ecord-frameset) and Italian-threaded Shimano Ultegra bottom bracket cups to go with it.

Annoyingly, the Shimano bb cups don’t seem to fit – they’re very tight and won’t screw in past half a turn. I’m guessing that the thread on the bottom bracket shell on the frame needs to be re-done. But it also crossed my mind that maybe the Shimano bb cups and Guerciotti frame aren’t compatible, despite the fact they are both Italian threaded???

Any ideas? Thanks!