Whitworth threading is perhaps the best threadform from a mechanical engineering standpoint. I haven't seen it on bicycles before but it is commonly found on British cars and motorcycles from the '50s and '60s.
The threadform has nicely raduised roots and crowns and thus avoids stress risers. In fact at least one F1 auto racing engine STILL uses Whitworth threadforms for the connecting rod and main bearing caps as they've been found to be more reliable! Hope this hasn't gotten too too OT. I DID say '50s and '60s!
Kurt "ain't stripped yet" Sperry Bellingham WA
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