What about the angle measurement? 360 degrees – why not 100 or 1000? Wiki says it’s probably because of the number of days in a year. Time to metricise?

That would be the radian. Very convenient for trigonometry and calculus, but possibly less useful in real life. I think there’s a pretty strong argument that 90º is easier to grasp than 0.5π radians.

The first time I came to build something with 2×4’s I drew up a blueprint based on having lumber that was actually 2” by 4”. Foolish innocent me.

S. Africa went metric in 1967, so I learnt British Imperial measures in primary school. My wife, 5 years younger than me, never did: so I still have to translate occasionally, usually recipes.

The only group of people in the US who use the metric system consistently (in multiple types of measurement and on both large and small scales) is the military (ok, scientists, too, but there really aren’t that many of them). And people who like the miltary aren’t big fans of rationalization/metric, and people who like metric ain’t that big fans of the military.

Historical reasons, obviously, but an interesting divide.

I’m not in a position to give authoritative advice on woodworking, as I’m famous for being all thumbs (and left thumbs at that), but in the rare cases that I need rough-and-ready precision somewhere between the millimeter and the half-centimeter I simply round up to the nearest even millimeter. In the distant past, when I used to do some metal milling work, we had measures with half-millimeter marks as well. Seems to me to cover more or less the same range with the same precision as your list.

The point is that with an english tape measure, you can easily choose a the degree of precision appropriate for any given measurement. Yes, 1/8 inch is about 3mm, but there are no repeated 3mm markings on any metric rule I’ve seen. The ones I’ve seen are marked only with cm, 1/2 cm, and mm. Of course it’s possible to build a wall, book-case, or deck that way, but it’s more of an inconvenience. Or at least, I found it less convenient to use metric for those purposes when I tried it.

Interestingly enough, Imperial has often persisted here as a way of measuring things of a personal scale. It’d be weird to tell someone your height in meters, your weight in kilos or your body temperature in degrees Celsius—but it’d be just as odd to tell somehow how many “feet” tall the CN Tower is, or how many miles it is to the next rest stop, or what the expected high temperature for the day would be Fahrenheit (indeed, they probably wouldn’t know what you’re talking about).

People are so accustomed to switching between systems for everyday use that it often doesn’t even occur to them that they’re doing so: one isn’t mentally switching gears to Fahrenheit in order to figure out body temperature, it’s just that that’s the way that particular thing is measured.

The meter was originally so defined because (a) one 40 millionth of the Earth’s circumference results in a unit of usable size comparable to the yard, the ell etc. and (2) more importantly it makes the definition and calibration of the unit distance independent of any particular physical “yardstick” stored in some monarch’s safe. The meter is now defined in terms of time and the speed of light. (All basic SI units, except for mass, are now defined in terms of universal physical constants. Only the kilogram is defined in terms of an actual, physical reference mass). In addition, Imperial units are also defined in terms of SI units. The foot is a derivative of the meter.

For woodworking and home repair, I find imperial measures to be superior. For most purposes, cm and half cm is too coarse and mm too fine—being able to halve or double precision of measures by switching between 1/4, 1/8th, 1/16th, and 1/32 inch is very useful as is the divisibility of 12 inches by half, quarter, third, sixth, etc.

I find this not wholly logical. The cm and half cm may be too coarse, but the inch is even coarser. Subdivisions of the inch mitigate this, but if the mm is too fine, then so are 1/16 and 1/32 inch. 1/4 inch is about a half centimeter, and 1/8 inch about 3mm. Wood and metal work functions just fine outside Imperial areas too.

The ‘advantage of fractions’ is just silly. Yes, you can divide 3/8 in two to get 3/16. So what? You can divide .564 in two to get .282, which is just as easy to do. You can get as precise as you like in metric but imperial measurements soon get unwieldy – who wants to talk about twenty-one one hundred and twenty-eigths when they could say .1640625? Who wants to multiply fractions with different divisors? And then go back to base 12 to step up or down a size?

British people (and Irish people) use feet, pounds and stone for everyday distances because its a common system used by people too old to learn metric, and it has a legacy effect. And if you’re talking about people’s heights, or weights – simple, imprecise measures that aren’t usually operated on – imperial measures are fine. But better? Hardly.

The Italian “etto” is a good metric ettogrammo, 100g, a bit light for a quarter pound.

> Because base 10 is simple. It’s not that a metre
> is a more ‘natural’ length than a foot, its that
> its easy to go from metres to kilometres to
> millimetres.

Any base is easy when you have a fair amount of practice. There was a time when I was using both base 8 and base 16 heavily, and I could do arithmetic in any of the 3 with no difficulty.

The problem is with the inconsistency of English/ANSI units, as you note. Over time I have come to believe that a base 12 system is preferable for measuring, but there is no doubt that it would have to be a consistent base 12 system.

Cranky