Comment by bsder | Hacker News Reader

Comment by bsder | Hacker News Reader

I suspect the issue is simply that there really isn't a driving force behind making "everything" metric anymore.

The original impetus in the 1970s was that it was costing a lot of money to maintain multiple systems in manufacturing.

CAD systems and automation make a lot of the issues moot. Everybody mostly converged to metric and let the CAD system put things in English for where you touch the legacy systems. CNC machines don't care whether you feed them metric or imperial units.

So, we're left with "imperial" in the US in things like highway signage, consumer recipes (businesses needing recipes already run by weight for consistency so the switchover isn't that relevant--scales easily do both), and housing construction. Note that there is expense in updating these to metric with no particular advantage accruing from doing so.

I note that one of the areas I never thought would become metric, consumer groceries, seems to be starting to change. Once this occurs, I suspect cookbooks will also start to change.

> CAD systems and automation make a lot of the issues moot.

Only sort of. Threads are probably the easiest counter-example, because single point cutting is much the same on CNC or manual lathe and while the CNC one can easily swap from 60 threads per inch to 5 per mm or whatever, cutting a 60° thread using a cutting tool that doesn't have a 60° point on it means another pass on every thread. Meanwhile the "imperial standard" is a loose collection of every thread ever and good luck to you.

The big win is communication. With metric it's rare to be working in metre-newtons per farad-volt-second but with imperial often the conversion from energy to power involves going from pound-feet to horsepower (etc). Much easier to say or write "1234 joules over 18 seconds is 89.2 watts". It's one less conversion as well as less to say, and that matters when you're stacking many of them then trying to use units to verify that it makes sense.

You also have the joy of "the hole for a 17/64ths Whitworth tap is 47.2 thou" or whatever other imperial nonsense machinists have to deal with. Meanwhile metric bunnies say "6mm tap therefore 5.1mm hole". Sure, you need a special drill bit in both cases, but honestly I'm just guessing at the imperial size and if I'm out by an order of magnitude I wouldn't know. But just guess... is 5.1 less than 6, yes or no?

> You also have the joy of "the hole for a 17/64ths Whitworth tap is 47.2 thou" or whatever other imperial nonsense machinists have to deal with.

It’s worse. The drill size for a 7/16” coarse tap is ‘U’.

In some cases, traditional units remain in use because they are more convenient than metric. This is a world-wide phenomenon, not just US/UK. In Japan, people still size farm fields in -tsubo and rooms in -jō.

Secondly, the world-wide conversion to metric is less thorough than claimed. In less developed countries, daily practice less often conforms to official documentation.

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