OldTools Archive

Recent Bios FAQ

271602 John Ruth <johnrruth@h...> 2020‑08‑13 Re: Rabone rule with "Tapping" and "Spanner" scales
“Spanner” will be the opening of the wrench which fits a bolt or nut with that
diameter of thread.

In the British Standard Whitworth system, the wrenches are marked with the
thread diameter which they fit, not the actual opening.

Some early USS ( United States Standard) wrenches are likewise marked for the
bolt or cap screw diameter which they fit.

John Ruth

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Recent Bios FAQ