120 is divisible by a lot of numbers, which is convenient for many calculations. There's a similar reasoning behind 24 hour days, 60 minute hours, and 360 degrees in a circle.
Now it is just "This piece is 340mm, I need to subtract 9mm and find the midpoint: 116mm": relatively easy peasy.
If you "normalize everything" you get the metric system (up to a scaling factor): all distances are expressed in metres, all energies in Joules, all forces in Newtons, all pressures in Pascals, etc. Note that the latter are just naming conventions (for kgm^2/s^2, kgm/s^2 and kg/ms^2, respectively).
This can lead to some unwieldy numbers, e.g. "turn left after four million 1/64 inches", so naming conventions are often used, like "mega" for "million".
Probably if I was a better woodworker I would have a solution for this without switching to metric.
Nobody who grew up with metric uses such measurements.
Outside of the US, metric measurements are usually to the millimeter (add decimal places for serious CNC etc work), not to some odd fractions.
The equivalent math is what they said: (340mm-9mm)/2. No weird fractions.
I hate converting between 3/8ths and 7/32nds all the time. It's such a stupid system, and I miss metric.
Walking is usually measured in pairs, many music systems in fours, many cooking measures in thirds, many art techniques in combinations of thirds and powers of two.
It’s also worth pointing out that as far as I know efforts to 10-base time have failed.
Sure, the French Republican Calendar "failed". But it "failed" less so because it was 10-base. Napoleon abolished it because of 2 main flaws:
(a) The decree that formalized the calendar contradicted itself when it came to determining leap years. (b) The beginning of the year/era was based on commemorating a historical event rather then observing the beginning of Winter or Spring. Which would make adoption of the calendar hard.
https://en.wikipedia.org/wiki/French_Republican_calendar
Then again, the traditional Chinese timekeeping was/is partly 10-based. This system developed in it's own right separate of systems that emerged throughout Europe.
https://en.wikipedia.org/wiki/Traditional_Chinese_timekeepin...
Time keeping is a "hard problem" anyway. As a historian, dating a historic document can be a daunting task when you're confronted with different calendars.
I don't understand this at all, but I want to. Is it that we use pairs of steps sometimes (single paces seem just as useful)? Walk out and back? Walk in groups of two?
[edit] I have no skin in this game - I grew up in England and America and literally don't care - just pointing out how weird the "2 by 4" terminology is
The advantage I'm talking about is what comes from having 12 inches in a foot. If you're only using inches and not feet then there's obviously no advantage from that.
It probably helped that I controlled the constraints so I could use nice whole numbers.
You certainly might have a point. I might just be noticing the "romantic" feeling for how clean it all seemed to be.
The main benefits of metric (actually SI) are:
- One unit for each dimension, e.g. all distances are in metres.
- The conversion factor between dimensions is 1, e.g. 1Nm = 1J, 1Pa = 1N/m^2, etc.
We often use prefixes like "centi" or "kilo", but they're just multipliers rather than separate units (SI calls them "derived units").
The main problems with metric are:
- Still some redundancy, e.g. litres, tonnes, hours, etc. These are avoided by SI.
- The base unit of mass is confusingly called the "kilogram". Hence any conversion factor involving grams will get a 1/1000, since the gram is 1/1000 of the base unit.
I wrote about this at http://chriswarbo.net/blog/2020-05-22-metric_red_herring.htm...
The choice of base 10 units is also completely arbitrary. So we have ten fingers? So what? That's not useful. Metric takes the view that everyone will work with arbitrary real number measurements, but we don't. We naturally use fractions. The fact you can't evenly divide a metric unit in three is terrible. If you look at standard sizes for, say, kitchen units in Europe, they actually are multiples of 6. A unit is 600mm and therefore divisible by 2, 3, 4, 5, 6, 8, 10 and 12. Wouldn't it be so much neater if we could just write 100mm instead of 600mm? We know humans can remember more than ten symbols because our alphabet is larger. Sigh... I suppose having one standard is better than a few competing standards or no standard at all.
Useful mnemonic, but completely arbitrary. If you cook/bake regularly, you know the standard amounts used. I know the amounts needed for a bread that fits into my rising basket, starting with 450g white flour and 50g rye flour, 350g water and so on. If you decide to go more advanced, you use baker's percentages anyway, which of course map neatly to a base-10 system.
> "The fact you can't evenly divide a metric unit in three is terrible."
The elegance of metric is that everything divides neatly into 10ths and powers of 10, which makes it simple to convert measurements from one scale to another, for whichever level of precision you require. Meters work for farming, centimeters work for houses, millimeters for woodworking, micrometers for machining.
Just as the common misconception of a 2x4" (really 1.5x3.5") becoming a bizarre 3.81x8.89cm is unrealistic and based on misconceptions, so is the idea of people somehow being unable to divide a metric measurement into thirds. Your pencil line is going to be thicker than any inaccuracy anyway, but the precision (repeatability) is going to be the same no matter which measuring system you use, as long as your measuring device is accurate. If you want a more accurate measurement and cut, you use a more accurate measuring device and scale.
I grew up learning and using metric for everything. Imperial may as well be an alien measurement from another planet, to me an inch is just an old-fashioned way of saying 2.54cm, and eyeballing a cm has literally never been an issue.
Regarding the kitchen cabinets, if you were to redefine 100mm as "the width of a kitchen cabinet", you would be optimizing for one specific use case over others. The entire point of a measurements system is that it is universal, repeatable and logical, not based on arbitrary units. 600mm is a perfectly good measurement, no harder to remember than 100mm or 20 kilometers or 250 grams.
Who needs easy fifth, other than musicians?
I had no previous experience with imperial measurements, my country is metric for over a hundred years, but the majority of information on woodworking on the internet or in print comes from English speaking countries that use imperial units in woodworking almost exclusively. So instead of trying to translate everything to metric I bought an imperial tape measure and a set of rulers. Since then I switched most of my woodworking measurements to imperial, because it just very convenient and makes much more sense when building items that will be used by humans. Chairs, tables, cabinets, chests, even guitars.
It's actually illuminating to trace the linguistic history:
- The 'hour' used to be the base unit for time
- Smaller intervals were called 'small parts', where a 'small part' is 1/60 of an hour (the sexagesimal equivalent to a 'decihour')
- Even smaller intervals were called 'second small parts', defined as 1/60 of a 'small part'
- Even smaller intervals were called 'third small parts', defined as 1/60 of a 'second small part'
- And so on
This was done by Latin speakers, whose phrase for 'small part' is "pars minuta". Hence 1/60 of an hour is a "pars minuta" ('minute' in English), and 1/60 of a pars minuta is a "pars minuta secunda" ('second' in English).
Metric/SI units take the "second" to be their base unit, and give us shorthand multipliers like "kilo". Tracing this back, we find that a kilosecond is 1000/3600 of an hour! Likewise we don't tend to use thirds or fourths anymore, instead using multipliers like "milli" and "nano".
I'm not aware of any shorthand multipliers for sexagesimal. In my blog post linked above I suggest “prota” for x60 and “defter” for x3600, so we could use "protasecond" instead of minute and "defersecond" instead of hour (I also suggest abbreviating second to "sec", since it's no longer used as an ordinal number ("second small"))