| Author |
 Replies: 10 / Views: 1,349 |
|
|
Pillar of the Community
United States
7066 Posts |
One of my projects this summer is to create a thorough list of antiquities I have been picking up. Measurement of each item will be listed in both US customary units (inches) and in the metric system (millimeters or centimeters). The sizes of the objects I will be documenting range from several inches to almost 20".
I am bit confused as to when to use mm's versus cm's. At what particular length does one switch from millimeters to centimeters? Is there a standard to follow regarding this? (I cannot detect such a standard based on dealers' listings - but I want some general rule to follow when cataloging)
For example, let's assume I have an object that measures around 6 ½". Is the metric equivalent better listed as 165mm or 16.5cm? If the latter, then how small would an object have to be to be properly listed in mm? In other words, at what size should the switch from mm to cm take place? Is there a norm to adhere to?
Any thoughts/help appreciated.
Edited by Kamnaskires
06/30/2019 11:25 am
|
|
|
|
CCF Advertiser
 United States
1306 Posts |
Edited by louisvillekyshop
06/30/2019 11:30 am
|
|
Pillar of the Community
 United States
7066 Posts |
Thanks, Joe. I'm just returning to CCF from a site where I happened to be looking at an ancient bronze piece that is listed as "200mm". So, again, there doesn't seem to be a definitive standard. But I do like your suggestion of >100mm perhaps being a sensible point of transition.
Edited by Kamnaskires
06/30/2019 11:47 am
|
|
Pillar of the Community
United States
1315 Posts |
I agree with changing at 100 mm.
Either way it's hard for me to picture the size of anything in my mind over coin sizes, 30mm or so without looking at one of my rulers.
Regards Bob
|
|
Pillar of the Community
United States
7066 Posts |
|
|
Pillar of the Community
 Canada
9865 Posts |
Don't use centimeters unless you're measuring snowfall or something similar where a degree of accuracy is not implied.
"Dipping" is not considered cleaning...
-from PCGS website
|
|
Moderator
United States
23731 Posts |
Bob,
To avoid confusion I would keep it as simple as possible and just use mm anything beyond 100mm use US measurements.
|
|
Pillar of the Community
Spain
2752 Posts |
That's a good question Bob!....Never really thought about this, being over here in decimal land, so I thought I'd ask a few of the Maths teachers here in the school... General concensus is up to 100mm then change to cm... BUT if you want whatever your describing to 'sound' more accurate 7.65cm rather than 76.5mm seems to be the standard at least here..... I personally would stay well clear of using the American feet and inches as it also slightly differs from the English equivalent and they've got enough to worry about at the moment!.....  Edit.. I think basically what they are saying is whole numbers up to 100mm use mm but if its fractional change to cm whenever possible Edited by Palouche
06/30/2019 3:38 pm
|
|
Pillar of the Community
Belgium
1194 Posts |
It is easy : 1 meter = 100 centimeter = 1000 milimeter so :1 m = 100 cm= 1000 mm , so : 1 cm = 10 mm. If small object ( a coin) : usr mm : milimeter : for example ,a roman denarius :: 20 mm ( milimeter) = 2 cm ( centimeter) l : 21mm = 2,1 cm. So I use for coins always mm,for objects of more than 50 mm always cm :5 cm and not 50. Mm I If there are more problems o will be at home at the end of the week.albert
|
|
CCF Advertiser
United States
1306 Posts |
The only standard is probably stay in metric as it is cruel to people who don't use the old English system. And if you really want to emphasize something is longer then the norm mm might be nice as you can make more of a point of the difference with mm than decimal differences in cm especially if you are over 100 mm. As an American I must say I am much more happy talking about only one thing in the old English system, and that is weather. We have 180 points between freezing and boiling of water where the rest of the world has only 100. So I think we can describe weather better in my personal opinion. But aside from that metric is better. I don't know if you folks dealt with significant figures in your careers but my students are told that something with hash marks you guess the last number between the marks and it is a significant figure and they always start the exercise thinking they like inches better than cm until I tell them to measure something in both and report the thing to the correct significant figures then divide the cm length by the inch length and you should get the 2.54 number. But the inch side of the ruler is marked off in 16th of an inch and they have to estimate to the 32nd of an inch then convert to decimal anyway to do the division of the cm length by the inch length and they get quite annoyed at my grading for the exercise. But they swore they liked inches better at first etc....
|
|
Pillar of the Community
United States
7066 Posts |
Thanks, all, for piling on with helpful and interesting comments. Much food for thought. FYI, the great majority of my acquisitions - certainly more than 90% - measure over 100mm.
|
| |
Replies: 10 / Views: 1,349 |
|
Posted 06/30/2019 11:46 am
