Metric vs Imperial units

[mr moda]

Crafts usually work to manual accuracies. When you start using machines that is where precision really starts, particularly when you work with numerically controlled machine tools as mass manufacturing does nowadays. Try to make a rectangular cut of 50 cm length with a hand held saw, even a powered one. You are not very likely to meet a mm accuracy. Same goes for stuff that gets made in a village forge or smithy.

There are always exceptions like watch makers, silver smiths, jewelers or makers of dental protheses but they are not the typical exponents.

Yes yes yes. There are always exceptions arent there

[WhiteBlue]

The point I'm making is that cm is an equally common metric prefix unit and SI prefix unit as a mm.



The cm may be under used in some countries for the reasons we have discussed. In traditional metric countries like France or Germany, Italy or Switzerland you find it in everyday use. Below you find an online postage calculator for the German postal service. It uses cm and mm as fit for the application.



A unit that is rather unpopular although also a legal SI unit is the decimeter. I do not know about a greater group of people using decimeters every day.

One odd ball is the kg. Usually all base units are without prefix. Not the kg. One suspects that it was the nearest metric mass unit to a pound. So the SI standard may have used it to keep the order of magnitude equal for the users that were familiar with pounds.

[xpensive]

I remember when we had a carpenter doing some work in a design-office where I was active in the 80s.

Carpenter finds a 100 mm gauge-block on my desk, why he goes;
- What's this shiny thing?
- It's a 100 mm gauge-block.
- So?
- I's a measuring device, we know it's xactly 100 mm long.

Carpenter takes his folding ruler, measures the block and says with a surprised voice;
- I'll be darned!

[tok-tokkie]

MM is an SI standard, Gugs. It's not just "those countries".

That is doubly incorrect.

The symbol for millimetre is mm. Symbols for units based on a persons name begin with capital letters (A W Pa N ...) The prefixes for factors greater than the basic unit use Upper case (M=mega, G=giga T=tera) but there is a glaring exception in the case of kilo which uses k (K=Kelvin temperature).

The SI unit of length is the metre not the mm which is 1/1000 of the standard unit.

I posted earlier that there is another glaring exception to the SI units. The basic unit for mass is the kilogram. In all other cases a kilo prefix means that it is 1000 of the basic unit. I questioned why a new name had not been applied to this unit. I suggested Archimedes but that would have used A as the symbol which conflicts with Amperes.

[Richard]

Mr. Juarizmi introduced people to zero and arabic numbers.

If only he'd had 12 arabic numerals, life would have been so much easier.

[mep]

Symbols for units based on a persons name begin with capital letters (A W Pa N ...)

Ahhhh somebody asked my this a year ago.
Something new learned today.

[Just_a_fan]

The point I'm making is that cm is an equally common metric prefix unit and SI prefix unit as a mm.

The cm may be under used in some countries for the reasons we have discussed. In traditional metric countries like France or Germany, Italy or Switzerland you find it in everyday use. Below you find an online postage calculator for the German postal service. It uses cm and mm as fit for the application.

The key word here is traditional. Modern metric countries use mm and m. Cm is old fashioned in the same way that the inch is old fashioned.

In effect, the cm is the European equivalent of the inch.

[WhiteBlue]

Modern metric countries use mm and m.

What you call modern is simply a phenomenon of late adopting SI units.

Cm is old fashioned in the same way that the inch is old fashioned.

If you say so. I'm not a great expert of fashions and I wasn't aware that using preferred metric prefixes is a subject to fashions.

[xpensive]

When I look in my EU-passport, my height is neither 0.178 m nor 1780 mm, but 178 cm. My mattress from IKEA is 90 times 210 cm and when I buy lunch at Subway the sandwich is 30 cm long.

But my stupid lap-top has for some reason an 11.6" screen.

[CMSMJ1]

Yeah, but why is the subway 30cm long?

It is really a foot long...

[Jersey Tom]

And here I thought this would be over in a page or two...

So basically, we've come to the conclusion that Imperial units are awesome, yes?

[xpensive]

Awsome as long as you stick to sandwiches rather than engineering perhaps...but seriously, Subway in Sweden uses cm.

[Pup]

MM is an SI standard, Gugs. It's not just "those countries".

That is doubly incorrect.

The symbol for millimetre is mm. Symbols for units based on a persons name begin with capital letters (A W Pa N ...) The prefixes for factors greater than the basic unit use Upper case (M=mega, G=giga T=tera) but there is a glaring exception in the case of kilo which uses k (K=Kelvin temperature).

The SI unit of length is the metre not the mm which is 1/1000 of the standard unit.

I posted earlier that there is another glaring exception to the SI units. The basic unit for mass is the kilogram. In all other cases a kilo prefix means that it is 1000 of the basic unit. I questioned why a new name had not been applied to this unit. I suggested Archimedes but that would have used A as the symbol which conflicts with Amperes.

The millimeter is the standard for engineering and architectural drawings, which is the subject at hand, or one of them at least.

[RacingManiac]

Awsome as long as you stick to sandwiches rather than engineering perhaps...but seriously, Subway in Sweden uses cm.

You guys have 30.48cm sub?

[mep]

And here I thought this would be over in a page or two...

So basically, we've come to the conclusion that Imperial units are awesome, yes?

This topic really became a runner.
Its strange some topics go on and on and when I have a idea for a good topic it becomes a epic fail.

The key word here is traditional. Modern metric countries use mm and m. Cm is old fashioned in the same way that the inch is old fashioned.

I disagree.
Most people use cm in normal life. It handles just better somehow.