I like it when someone tells me they're better working in inches than metric so I give em a size like 2'6" and 17/32nds. After a minute or so of them faffing about trying to find it on the tape measure I point out they're just hopeless at measuring and we can get back to metric.
Or I give em sizes in cubits, just out of badness.
If you asked me to find 2' 6" 17/32 on a tape measure or rule, I could point it out to you, straight off, even if the tape measure / rul was only marked in eighths of an inch.
What few people seem to grasp these days is that, pre-metric, nobody needed to know
all of the old measurements; once you started work, you learnt the ones you used in your job and ignored the rest. So fencers, hedgers and ditchers, landscape gardeners, and dry stone wallers worked with rods and chains - because they were the handiest sized units for them to use in their job. Boatbuilders ignored rods and chains, because feet, inches and eighths of an inch were the handiest units of measure for them to work with. Woodworkers went down to quarter inch, eighths or sixteenths, depending on whether they were carpenters, joiners or cabinet makers, and so on.
Those different measurements weren't dreamed up by some academics - nor were they based on an incorrect measurement of the circumference of the Earth (as though anyone could calculate that accurately in the 18th century!). They were worked out on the job by working people, and the units chosen were PRACTICAL for their particular job. Also, the sub-divisions of units gave you a useful graduation of measurements, instead of the 'everything divided by ten, whether it fits or not' approach.
The range of drill sizes in the old system is a classic example; smaller drills were in the numbers range, larger ones in the letters range. If you look at the dimensions, they might
appear to be chosen at random; in fact, they were chosen so that each step in size was the same percentage up or down, rather than a fixed jump in size of '1mm or 0.5mm'. In the smaller sizes of metric drills, those steps are too big - in the larger sizes, they're too small.
And as for metric threads . . .
I used to work in an engineering drawing office, and my boss Henry (the production engineer) was Swiss. He'd done his degree in production engineering in Switzerland, and told me about a lecture they'd had on thread forms. The professor put a HUGE silhouette up on the projection screen, showing the profile of a Whitworth thread (about 6 feet from top to bottom), with all the dimensions and radii marked up, and went through it point by point.
He summed up by saying that Sir Joseph Whitworth (who he described as an engineering genius) had done such a perfect analysis of the loads on screw threads that
nobody had ever designed a stronger bi-directional thread form than that. Then he put up the silhouette of the Metric threadform, on the same scale, beside the Whitworth - and Henry said he cringed at the sight of it!
The professor went through the details of the Metric threadform like a devouring flame, absolutely savaging it on every aspect. Finally, one of the students asked him the obvious question; what were the positive points about the Metric thread? He got the blistering answer:
"It only has ONE point in its favour!", the professor barked, "It's
CHEAP! And I am utterly ashamed that so many fine and precision engineering companies in Switzerland use such a crude design of thread, which belongs in the field of cheap toys for babies!"
It's worth noting that, in many specialist fields, particularly where you need a thread which engages easily and reliably, the Whitworth thread is still in use. For example, if you have a tripod for a camera, the screw thread used on it is a Whitworth thread, and Whitworth threads are also used on the supports for the massive and heavy overhead lights used in theatres.
