Sanderxpander said:
I don't mean for anyone to take this the wrong way but as a born and raised metric person (The Netherlands) to hear the centimeter described as "confusing" (vs feet/inches/fractions) is a bit bizarre.
CMS has basically been replaced by MGS globally. From personal experience and from other discussions here, it's understood areas around the Netherlands do use cm a fair bit, but globally it's not the norm. Centimeters don't work well with the rest of the system as they are a kilo, mega, etc 3 place shift. Just like how decimeters are not used. In the US centimeters are often brought up when go over metric with kids, and tend to be spoken by people who don't use metric. For those who do use metric a lot, they are almost never used. Often they can't be used because the field or contract simply won't allow them. Also tools (software) is default mm. Engineering drawings if in metric are mm-kg-s. As others mentioned, usage of cm is in general a casual usage thing, not something people would generally use operationally. Not really any different than how Yards are perfectly valid in the inch system, but you don't use them on drawings, design, etc. But in casual usage for how far away something is, sure.
Centimeters defeat one of the primary benefits of metric over inch. With mm, almost everything you do is whole units, not decimals. Needing less than 1mm is un-common, yet 1mm works out nice as a base thickness. Even in engineering work it's nice as most all dimensions are whole mm numbers. Not many things get over 1m, and when they do mm still work fine up thru 10m. 1mm is ~.040" which is a classic big tolerance, and 0.1mm is a good tighter tolerance limit .004" (aka about 1 sheet of paper). So designing stuff you are always in mm, and only introduce a decimal on things where you have to like hole tolerancing, surfaces, profiles, etc. It just works out really well. We don't say 1cm bolt, or 1.8cm bolt or 0.6cm bolt, we say 6, 10, 18mm bolts, it's just so much cleaner/easier. 0.5mm pencil comes across much better than .05cm pencil. Centimeters mean you loose that and now have a decimal place all the time, now your back to the same headaches as inches.
Using cm and mm together gets real confusing. This is where the tape measures cause problem. You got a number in your head say 1106mm, you go to your cm tape and go past 100 (the 1 meter mark) to 106, make mark. Now you just messed up, you are off by 46mm. You ended up making your mark at 1060mm, not the 1106 mark you intended. You have just killed the beauty of metric.
Since stuff when listed with it's proper metric designations are listed in mm, introducing cm to the mix is a headache and its the very thing that causes people not to want to work in metric. Almost universally those I find who hate metric or find it dumb speak of cm when pointing out the issues/flaws and to some degree they have a point. Where those who do work in mm, almost never use/speak of cm. Tape measures are this strange thing where ones that are metric tend to be cm, which is just annoying since nothing else metric is listed in cm. Thankfully Festool doesn't recognize cm and sticks to mm (except when they ditch metric all together).
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