Originally Posted by Trakhak
You're confusing Italian threading with ISO threading (as did Hillrider in his post above). For track cog or freewheel threading, the ISO standard is not just compatible with British threading: ISO adopted British threading dimensions for their rear hub threading standard. "Compatible" in this case means identical. There is no difference between ISO freewheel/track cog threading and and British freewheel/track cog threading.
That's basically correct. There is theoretically a 5/1,000" difference in diameter, too small to matter in practice.
This bit of misinformation came from Surly...The early versions of Surly's track sprockets had insufficient thread depth, and they wrecked some hubs. Surly initially came up with this theory about a threading difference to explain the problem.
Ultimately, Surly revised the design of their sprockets to provide adequate threading, and the problem disappeared.
Sheldon "No Problem" Brown
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