Haven't need Whitworth for the US Triumphs since the 50s, they changed it all to SAE back then. There is always a chance for error weather using metric or not. Just add one more steo and extra chance for error by using SAE gauges. Hey, I like living dangerously. I have a set of metric but the graduations are too far apart for my liking, my SAE are in smaller increments.

I learned all I need to know about life by killing smart people and eating their brains.
Eat right ,Exercise ,Stay fit, Die Anyway!