Soren,
Some background from an equally uninformed Yankee
WHITWORTH adj. - A type of thread not to be confused with the BSF thread (British Standard Fine, or colloq. British Strip Fine), and not interchanged with SI or SAE threads as used by the developed nations of the world. The selection of suitable wrenches for use with Whitworth fasteners is sometimes confusing to the novice, but is greatly simplified if these few rules, which are completely true and correct, are committed to memory:
>Whitworth nut sizes are not even in fractions of an inch, except in certain cases where they are:
>A Whitworth wrench is not the size marked upon it and will not fit a nut of that size, though it will fit a nut which fits a bolt that is almost, but not quite, that size.
>A Whitworth wrench of a given size will fit the nut that fits a BSF bolt of 1/16 inch larger nominal diameter, hence of approximately 1/16 inch larger actual diameter, than the bolt that fits the Whitworth nut the wrench fits.
>Some Whitworth, SI, and SAE wrenches fit some Whitworth, SI and SAE nuts and others definitely do not.
There was some additional info I had posted long ago in the archives that had some of the history as well.
