The Whitworth 55 24G blade looks like a very
good fit to the crank thread but having it
perpendicular and holding the crank and
thread gauge to a light bulb I do see some
light shining thru so perhaps that's it?

I just now did the same thing with an M8 bolt
and the metric 1.25 pitch blade from the same
thread gauge and there were light there as
well, just a little but still, so perhaps one
shouldn't use that method when in doubt...

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