AFAIK, everyone or almost everyone measure skate ROH (Radius of Hollow) and Rocker radius in fractional inches and feet. E.G., MK and JW specified their blades that way (though they no longer specify or pre-grind ROH for high level blades), even though they are located in Sheffield, UK. And, at least on the sharpening machines with dressing systems that I personally have seen, the scales were marked in fractional inches. But I think I once saw someone specify Rocker radius in metric units, so maybe I'm wrong.
That said, there are extremely good reasons for people to use metric - not just trivial one of making it easier to use base 10 arithmetic. A bigger problem with inches, feet, statutory miles, nautical miles, ounces, pounds, tons, and the square and cube equivalents, is that they have had many somewhat different definitions, at different times, as well as in different countries.
E.g., one Scandinavian country currently defines 10 inches per foot, but AFAIK all others use 12 inches per foot. The U.S.A. alone has used at least 3 different definitions of inch, foot, and statutory mile, and still uses two. (Those two only differ by 2 parts per million - the current U.S. legal inch, which the USGS called the international inch is 2.54 cm; but many map makers, including the USGS, and most but not all US state survey offices, and AFAIK all nominal runway lengths, still use an older standard, that the USGS called the "ground survey inch, 1/39.37 m. Congress created a special "temporary" exception for the USGS, so they didn't have to redraw all their maps, and the USGS tried hard to convince other U.S. mapmakers to follow them, and to make "temporary" permanent.) Various countries also still define the nautical mile - which was originally intended to be the approximate average size of a minute of latitude in the ocean near Germany - in different ways. These sorts of things matter significantly if you use large scale gridded maps, especially UTM maps.
Wooden boards are often measured approximately before kiln drying, and so are substantially smaller than the nominal sizes at the store. Plywood and particle board are always made smaller in the first place. I'm not sure if that is true in countries that use metric units. E.g., do metric countries still use "2x4s"?
Likewise for square and cubic units of area and volume, as well as acres. And we in the U.S. sometimes use other units for volume, like teaspoon, tablespoon, pinch, bushel, peck, etc.
The U.S.A. still uses at least two definitions of ounce and pound" - avoirdupois for most things, troy for precious metals. We mostly use carets for precious stones.
Even degrees, minutes and seconds of angle, when it comes to latitude and longitude can be very complicated, as there are many different ways of measuring them (in public school I was taught about geocentric latitude and longitude; I learned later that geodetic and astronomical coordinates are more common), as well as different estimated sets of reference points (e.g., points on the earth, and the earth's center, and different era nominal poles and equator) that have differently defined values, and between which other values are interpolated. It's enough for a poor navigator to run aground, be arrested, have their ship confiscated, or be tortured to death as a spy, if they fish or in some cases just enter the wrong national waters or territories. Remember the U.S. spy plane that China forced down a while ago, and the U.S. hikers that Iran arrested and imprisoned (maybe worse) as spies? I wouldn't be surprised if they inappropriate used a U.S. market GPS set to one or another version of WGS 84 latitude and longitude with maps that were drawn in some other coordinate system. You could easily run aground if you use NOAH nautical charts (which are all old, out of date, and in many cases no longer meet the U.S. must-carry provisions) with a GPS that uses WGS 84.
(Unfortunately, there are no metric systems for latitude and longitude, and even metric unit altitudes can have different meanings depending on origin baseline and projection direction. And reference points are revised by a committee after major geological activity, and/or big asteroid impacts. So they will remain messed up.)
Horsepower too - last I knew UK uses 550 ft-pounds/minute; USA uses 746 watts, both of which are far less than a horse, or even a fit person, can generate in the short term. Except - marine engines are measured very inconsistently, often differing from true used or effective power by orders of magnitude. Some marine motor makers even use propeller force while standing still to measure power. If the ratings were actually correct, many marine motors could be connected to a generator to create much more power than they used, which would be very useful.
Metric units are so much better. They have changed much less over time, and AFAIK are the same in all countries.
E.g., shoe and boot (including skate boot!) sizes differ country to country, manufacturer to manufacturer, sometimes even model to model, as well as by age and gender groups - but are much closer to be standardized for those who measure in metric mm. (Of course assumed foot shapes and bottom tilts are still different.)
Topic: A way to center a sharpening machine on the blade (Read 7312 times)