Italian vs ISO freewheel thread
 

I assume the Caimi freewheel and Campag. rear hub on my newly-acquired 1960 Capo are Italian-threaded. (Except for the ISO BB, Capos are essentially Italian bikes, with almost all-Italian components, which were soldered and assembled in Vienna, using British tubing and Italian lugs.) I also BELIEVE the Regina America freewheel and Ofmega hub on my 1981 Bianchi are Italian-threaded. Does anyone know when Italian freewheel threading (same as ISO except for the 55-versus-60 degree thread angle issue) was discontinued? I don't see any "BSC" or other identifying marks on any of my hubs or freewheels, but I suspect my Italian hubs and freewheels are Italian-threaded and my Japanese and French hubs and freewheels are ISO-threaded. (Fortunately, I have no French-threaded hubs or freewheels anymore!)

IIRC the French threading is different, it's "French", and metric, whether that's considered ISO or not on a hub/freewheel, I don't know, but the Japanese standard is/was to copy the British (BSC) standard of 1.37 inches by 24TPI and that's virtually the same as the Italian except for the actual thread angle. In my experience I could always interchange the BSC and Italian threaded objects as long as I was careful and used plenty of grease. I only heard the term ISO applied to the taper of non-Japanese square-tapered BB spindles, tho I know ISO standards apply to many other manufactured goods outside of the Bicycle realm.

Of course, after reading this I have to add that it don't apply to BBs where the Italian shell is 2mm wider and the British/Japanese shell has LH threading on the fixed cup side...Doh!

I am excited to see the definitive answer. I have a British freewheel from the late 50's (Cross) and it has no indicator of threading at all. I suspect that the indicators were a 60-70s addition, mostly. I have never seen a real Italian threaded freewheel, but the thread difference would be almost instantly noticeable, wouldn't it?

Italian-thread freewheels use 24 TPI and a 35mm = 1.378" diameter, which is virtually the same as the ISO standard of 24 TPI and 1.375" diameter. However, because the threads are cut at a different angle (think of them as sharper "teeth" in profile), swapping back and forth between Italian and ISO will presumably erode the aluminum threads on the hub shell, leading to potential failure on an out-of-saddle climb or sprint (ouch!). In my experience, mismatched freewheel/hub sets put up a bit more resistance than normal during assembly and disassembly.

Yes, French-threaded freewheels are completely incompatible with Italian and ISO, and blessedly rare in the U.S. (I had one on a circa 1980 Carbolite 103 Peugeot, which also had Swiss BB threading.)

When Campagnolo stopped making freewheel compatible hubs? Seriously, it takes a lot to make the Italians give up on their bicycle technology, namely a big loss of market share. After all, we still have Italian bottom bracket threading. The industry generally follows the practices of the leaders, namely Shimano and Camapgnolo. In Shimano's case, they realized the similarities of the English & Italian threading and never did offer Italian threaded hubs or freewheels. Campagnolo, on the other hand, did. Campgnolo catalogs as late as 1984 (#18) reference Italian threaded hubs, so presumibly the Campagnolo freewheel and Regina models were still offered with this option. The 1991 catalog shows that Campagnolo had finally switched to freehubs. I'm not sure about the 7 year interval, but it wouldn't suprise me if Campagnolo and Regina offered Italian threaded hubs and freewheels right up to Campagnolo's freehub introduction. Regina may even have offered them for a few years more, for retro-fit.

While researching this, I came across another interesting piece of info, especially considering that Shimano is so often accused of incompatibility issues. As late as 1993, Shimano still offered French threaded headsets.

Regarding the Italian/English freewheels compatibility issue, our rule of thumb was that you could place an English threaded freewheel on an Italian theaded hub (or vica-versa), so long as you did not later revert to a freewheel with threading that matched the hub.