Campagnolo Cog Threads
Recently, I built up a NOS set of C-Record HF Hubs, and wanted to make sure everything was hunky dory, in terms of the cog thread interface. After an evening of comparing cog threads amongst different hubs and cogs I have on hand I'd like to give a few small notes on cog threads to prevent other users from screwing up their cog threads.
-The C Record hub threads are 1.37" X 24tpi. Newer record hubs are 1.37" X 24tpi. From what i can tell, the c-record era is the turning point in cog threading for campy hubs. Older low flange record and high flange record seem to be split between italian thread 35 x 24F and british 1.37" X 24tpi thread. Perhaps other campy heads will want to chime in about this.
-I have a set of beat up high flange record hubs. they *appear* to have been italian threading, and someone had thread on a steel british cog, basically chasing down the threads from italian to british. (insert world cup jab here). All of my british cogs thread on nicely, however the original campagnolo cog 35 x 24F which came with it, threads on quite loosely.
-The italian threaded cog 35 x 24F threads on the newer c-record hub 1.37" X 24tpi, however a tiny bit loosely. The campagnolo italian thread cogs are marked "italiano 35 x 24F", whereas the british thread cogs read simply "made in italy". however, i also have one british thread campagnolo 13T cog which has no text at all as there is no space to engrave.
-I have an identical looking set of high flange record hubs, they are in better condition and have never had another cog threaded on. the threads are definitely 1.37" X 24tpi, and the cog is a newer campy one. the cog interface is perfect.
-I had a 18T EAI cog (1.37" X 24tpi) which i intended to use, on the c-record hubs. The cog threaded only 95% on. It left a small 1mm gap between the hub body and cog. Of all the other cogs i have, campagnolo, suntour and dura ace, none of them had this problem. I threaded the cog onto a bottom bracket chasing tool, to clean up the threads. A bit of cutting oil, and a few minutes later and it spun on like butter.