The Italian thread is 1.378" in diameter (35mm) vs 1.370 nominal for the British threaded cog. Plus a 55 degree vs 60 degree thread angle so a little bit too much metal there too. Add to that the poor tolerance of the TDC cog and it sounds like it just won't fit. I think you are stuck here as to a homemade tap because an Italian BB cup is 36mm. I could try another cog as you could get lucky if it was tapped with a fresh tap when made. I think TDC had the same tooling and machines from 1900 when they went out of business.
Joe Bender-Zanoni Whitneyville, CT
---- sage ----- From: "Amir Avitzur" <walawalaoxenfree@gmail.com> To: classicrendezvous@bikelist.org Sent: Saturday, December 12, 2009 12:23:17 PM GMT -05:00 US/Canada Eastern Subject: [CR] Fixed cog on Std FW Hub - help needed
A friend recently gave me an old Atala frame painted in Repsol colors.
http://www.flickr.com/
Perfect for a "fixed" gear.
I threw the bike together using whatever was an hand, and a freewheel, hoping to replace it with a large single cog + lockring.
It turns out that I had an old 22 tooth TDC cog that should work ... but doesn't.
The first problem was that the threads weren't round ... so I took a British threaded adjustable cup, and ground some slots into it, converting it into a home-made tap. Then I re-tapped ot the threads.
I got to the point where mounting the cog on an old british steel hub went smoothly.
But the cog still won't screw on a Campy hub with ITALIANA 35 x 24P threads.
I do not want to mess with the hub threads. What can I do?
Amir Avitzur
R"G Israel