> I typically prefer imperial measures in simple projects because they tend do feel more practical.
I posit that you almost definitely prefer imperial measurements because that's what you grew up with, and consequently have the most familiarity, experience, and comfort with.
And that's okay.
But it doesn't speak to objective practicality.
Papercraft - somewhat aside, have you looked at how ISO A series paper sizes [0] are determined? Now that's an exercise in gorgeous and thoughtful standards design.
I'll point out that I do a fair bit of woodwork too, and my equipment - rules, squares, drop and band saws, router table markings, screws, bolts, drill bits, etc - are all metric. I have a tiny number of imperial items (eg a dovetail jig from a company in North America) but they tend to not have to interact with any metric gear, and finding metric versions of these tools is difficult/expensive.
All of us metric-only people (let's say ~95% of the world) are just fine using what they grew up with to make & build stuff -- so it's going to be hard to demonstrate that imperial is 'more practical'.
I feel I should share this -- it's an explanation provided in the Leigh dovetail jig manual for why two things share the same scale. Leigh's based in Canada, which appears to be nominally metric, but I gather most of their market is the other part of North America (which obviously isn't).
I bought the metric version of this jig - and I'm ecstatic they make this. The metric measurements are just different scales & translations - they didn't redesign the device at all.
Decimals don't slow me down, but comparing fractions with different denominators does.
Most of the manual they mention metric values in parenthesis, but in some sections it seems the authors just, understandably, gave up.
I'm perversely envious of people who can effortlessly make sense of this:
"""
Section 8-23 : Why are the 1⁄2" and 11⁄16" [12,7 & 17,5mm] pin widths on the same scale line?
1⁄2" through dovetails are routed using a 7⁄16" guidebush.
11⁄16" through dovetails are routed with a 5⁄8" guidebush.
That's a 3⁄16" difference in size between the two bits ... and between the two guidebushes.
The 5⁄8" diameter guidebush for 11⁄16" joints requires that the guide fingers be opened up by 3⁄16".
This automatically makes the pins 3⁄16" wider but on the same scale setting.
This is clip of the reality show American Chopper, where a bunch of native imperial unit users, professional mechanics are trying to calculate fractions: https://www.youtube.com/watch?v=EUpwa0je6_Y
This conversation would never happen in a metric shop if the people there are above 2nd grade in their arithmetic skills.
That was hilarious, though the problem was the older guy kept changing his measurements, not the actual calculation. (I don't even use Imperial and was able to calculate the difference in my head as he said them (the young guy was correct each time)).
I agree that (at least part of) my preference comes from familiarity but I am not convinced that it is caused 100% by familiarity.
I happened to see this brief interaction in a video [0] the other day that pretty accurately illustrates my point of view. In summary: 2 makers (one german, one american) working on a device are looking at parts in hand to design as they build and one says "...if you put this 15 millimeters in from the edge. about half an inch". They first physically see/feel the distance they believe to be correct is 1.5 or 15 metric units (cm or mm) or 1 imperial unit (half inch). This is the case I find comes up frequently for me. Measures where moving a cut to line up to whole cm is too far and I end up working with half and quarter centimeters or awkward counts of millimeters.
Though, it is definitely possible that 15mm only felt right in that case due to familiarity with imperial measures and that 1cm or 2cm would have been fine.
I guess the "trick" is that even though 1/16, 1/8, 1/4, and 1/2 inch are all technically divisions of an inch, they all function in practice as distinct whole units that are (typically) easily converted. So when you are doing work in that scale range you have many options to match what you are working with.
Paper sizes are also another good example of what I am talking about. An imperial "letter" size page is 8 and 1/2 by 11 inches. To cut one in half in either direction, the calculation is easy: horizontal 8 divided by 2 is 4 plus 1/2 divided by 2 is 1/4 or vertical 11 divided by 2 is 5 and 1/2.
The similar ISO size (A4) is 210mm x 297mm would be cut at 10.5cm or 14.85cm. Sure you could just pull two A6 out of the drawer instead of cutting one A4 but then you are using ISO216 as your units of measure instead of cm/mm. In terms of practicality, cutting material stock in half is a pretty basic operation.
Can I ask why you consider consider 0.5 inches to be 'one unit' - but think 1.5 cm is not?
For me, a unit is akin to atomicity.
But units don't dictate what size something is or should be - that's what multiples are for.
> Measures where moving a cut to line up to whole cm is too far and I end up working with half and quarter centimeters or awkward counts of millimeters.
It's a poor tape measure that does not show mm.
Similarly it would be a poor tape measure that does not show 1/32 of an inch.
The fact that your measuring device shows these gradations doesn't mean your design needs to be aligned to any arbitrary subset of multiples / divisors though, surely?
> I guess the "trick" is that even though 1/16, 1/8, 1/4, and 1/2 inch are all technically divisions of an inch, they all function in practice as distinct whole units that are (typically) easily converted. So when you are doing work in that scale range you have many options to match what you are working with.
1/16th of an inch isn't just technically a division of an inch. : )
When you're working down to something tiny, both measurement systems will be able to represent absolute distances just fine - do we agree on that?
It's a matter of whether manipulating those numbers is easy or difficult (for me, working with wood almost always means working with integers - mm - so all calculations are delightfully easy). Refer my other post about the Leigh dovetail jig description of router bit and bush sizes - there's 4 different dividends in use in just that one short paragraph, so you have to convert them all to common denominators before doing any mental arithmetic with them.
> When you're working down to something tiny, both measurement systems will be able to represent absolute distances just fine - do we agree on that?
Yes. I guess it was implied by omission but I don't think either system is bad. My original statement was: "I wouldn't call imperial measures 'broken'"
> Can I ask why you consider consider 0.5 inches to be 'one unit' - but think 1.5 cm is not?
>1/16th of an inch isn't just technically a division of an inch. : )
Because I don't think of 1.5 inches as 1 inch + 0.5 inches, I tend to think of 1.5 inches instead as three 1/2-inches. What I mean by stating that while 1/16 is (and 1/2, 1/4, 1/8 are) "technically" divisions of the inch, they are _practically_ (or effectively) separate whole units that you step up or down to the same way you convert up or down between mm and cm.
I find sub-dividing material (or design) by a power of two to be very common. Working with metric units, this tends to always lead to handling multiples of 5 which I tend to find more difficult than handling multiples of 2.
Working with imperial inches and subdivisions of an inch in this way (for "normal" sized projects of the type mentioned in previous comments) means there are more options to match "whole" units to the specific measurement and you generally make new measurements in your work by changing units and adding/subtracting integer values of that unit. It is literally practical because it was derived from existing practices and matches them inherently.
I posit that you almost definitely prefer imperial measurements because that's what you grew up with, and consequently have the most familiarity, experience, and comfort with.
And that's okay.
But it doesn't speak to objective practicality.
Papercraft - somewhat aside, have you looked at how ISO A series paper sizes [0] are determined? Now that's an exercise in gorgeous and thoughtful standards design.
I'll point out that I do a fair bit of woodwork too, and my equipment - rules, squares, drop and band saws, router table markings, screws, bolts, drill bits, etc - are all metric. I have a tiny number of imperial items (eg a dovetail jig from a company in North America) but they tend to not have to interact with any metric gear, and finding metric versions of these tools is difficult/expensive.
All of us metric-only people (let's say ~95% of the world) are just fine using what they grew up with to make & build stuff -- so it's going to be hard to demonstrate that imperial is 'more practical'.
[0] https://en.wikipedia.org/wiki/Paper_size#A_series