Fixings - Metric vs Imperial

[Tony Press]

In 1919, when supplies of the White & Poppe engine fitted to the Morris Cowley dried up, Morris turned to Hotchkiss et Cie to supply. Based on the US Continental Red Seal engine, didn't the metric fastenings used have British hexagon heads?

Err! I wrote earlier :

"Didn't Morris use British standard heads on metric threads ?'
 
Mike Costigan wrote in reply-

"Yes they did; that was a legacy from acquiring the Hotchkiss Engine Company, which was of French origin. Prior to using the Hotchkiss design, the early Bullnose with the American Continental engine used a bewildering mixture of BSF, Whitworth, Metric and American Fine threads.
Similarly Georges Roesch used metric fittings with imperial heads on his Talbots."

[Erich]

Yes, Bob 46320, the BA was based on the metric Thiry thread, which was developed in Switzerland for the clock making industry. Once it became BA, it was a new thread. Since Whitworth and BSF don't go very small, there was a need for a small thread. Which in BA gets very small. I agree that adding metric coarse, fine or super fine or UNC, UNF, or UNEF fasteners adds to the already numerous thread pitches on the Austin Seven, which if my counting is correct, is six different thread forms.

Erich in Seattle