terms used for centimeters 3

[toolmantwo]

Question on terms used for centimeters
I have a tool we make that has a scale with graduations in English (inch) system and also metric system.

For the input of those of you who use the metric system frequently in the daily language, would a person relay a dimension to another worker verbally as 10 and one half Centimeters or instead say 15 Millimeters?

On the tool the scale used is actually ½ scale because the tool works off the radius to produce a diameter in direct reading. IE the graduation says 10 CM to make a 10 CM diameter hole (but the true distance of the scale is 5 CM). Because it is ½ scale and we want to keep the numbers large enough to read, the graduations and numbers are limited. Currently we only show the whole number as 10, 11, 12 CM with lines between them for .5 and .25 CM increments.

Your thoughts?

 

[CanEngJohn]

Interestingly enough in my work I don't ever use centimeters. I use either m or mm.

In your case however I would not even use the units when I read off the scale. If it read 10.5 then I would call it 10.5 and worry about the units later.

I always find that on the spot conversions are usually accurate to +/- an order of magnitude. Your written conversion illustrates this perfectly - 10.5 cm is 105 mm not 15 mm.

 

[TheTick]

I never mix fractions with metric. I would phrase it as "Ten point five centimeters".

Due to illness, the part of The Tick will be played by... The Tick.

http://www.EsoxRepublic.com

 

[MintJulep]

Aren't mm the prefered (by ISO, or whowever is in charge of the metric system) term?

 

[CoryPad]

CanEngJohn and TheTick are correct -- use 10.5 cm or ten point five centimeters or 105 mm, certainly not 15 mm.

MintJulep,

Millimeters are preferred over centimeters, but centimeters are allowed. The International Bureau of Weights and Measures (BIPM, for Bureau International des Poids et Mesures) is in charge of the SI.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[notnats]

Centimetres might be allowed, but in this country engineers only use them when buying clothes (I have a 97 cm waist.) All engineering measurements are mm for machinery (an 8ft x 4ft sheet of steel is 2440 x 1220mm)or m for bridges and dams.

Jeff

 

[gearguru]

toolmantwo,
10 and one half Centimeters would be 105 mm, not 15mm. See, one more reason not to mix units: error in conversion, even so simple as multiplying by 10.
But as said by other folks here, in engineering (especially mechanical) the mm is the king. In "civil" life, in my old metric country, we talked in cm; Also the architects used cm as a unit. The athletes were jumping over 200 cm high etc, While the discus could fly 50 meters and 26 cm...

 

[tygerdawg]

hee hee and now for a little bit of levity

I read an editorial once upon a time in some trade rag. The guy was metric-ignorant and was trying to pretend he wasn't to some German engineers. He described his work as thus&so-many centimeters. The German yelled at him that "Engineers use millimeters...carpenters use centimeters!"

My experience bears that out...in machine design, automotive, who knows, maybe even airplanes....it's all millimeters.


TygerDawg

 

[djw2k3]

Tygeydawg - LOL

From another metric native I have never seen centimeters(or centimetres) on an engineering drawing.

And if in a fab/machine shop that measurement is probably referred to as 15 mil ;-)

 

[GregLocock]

Which of course will cause a problem in a USAn machine shop.

http://www.thefreedictionary.com/mil

where a mil is .001" , or roughly 0.025 mill

imetres



Cheers

Greg Locock

 

[toolmantwo]

OK people, If I understand the answers I would say most people would say 105 MM rather than 10.5 CM correct?

If that is more "correct" should my scale read with MM and not CM?

If so, I would then need even more room to place the numbers in more digits and they would nearly touch each other.

Example: my current scale has numbers 3 MM wide for the two numbers like the 12 of the 12CM mark. We skipped the odd numbers like 1, 3, 5, 7 ......and only show the even numbers 2,4,6,8 .... of the CM scale. We did this because the scale is 1/2 scale the current numbers are 10MM on center, and at 3MM wide for the digits 12 can be read well and we paint the whole part. The lines and digits of the scale are raised above the surface of a die casted part.

If I use MM instead of CM at the 100MM mark, the number 100 alone would be 4.5MM wide, using up the space of the progression of 5MM total, not good for visual conformation.

I think MM is not well suited for this scale, yet MM is the more common expression a worker may use to communicate to another worker rather than CM.

Thanks

 

[sreid]

Clearly in science and engineering the prefered units of measure are in powers of 3. Having said that, I don't see any reason to not use any common unit of measure and centimeters is one of them (decimeter would not be one). Certainly it defines one common fundamental measurement system (CGS Centimeter-Gram-Second). And my TI-36 calculator converts centimeters and inches.

 

[notnats]

Toolmantwo,
On my lathe the cross slide is direct reading (ie 1mm =1mm cut). 1 turn of the dial = 2.5mm (the screw is 2.5mm pitch.) The dial is graduated in 0.01mm marks with a larger mark at 0.1 mm. The larger marks are numbered every 5th mark 5, 10, 15, 20, 25. It is obvious that the larger marks are tenths of a millimetre, but the manufacturer has engraved:
->0.01mm<-
alongside one of the smaller graduations just to be sure.

My vernier calipers are marked every 10mm : 1,2,3,4,5,6,7,8,9,10, etc., ie in cm but the measurement is always read in mm

Hope this helps

Jeff

 

[IRstuff]

Why not go to you local hardware store and look at a metal ruler?

Mine is marked in millimeters, with notations every 10 millimeters, and every 5 millimeter rule is longer. With the proper rule lengths, there is no need to notate the lines that closely.

TTFN

 

[CanEngJohn]

toolmantwo

If you are calling out a scaled specification between two people to use on the same equipment I would NOT use any unit designation. I would call out what the reading is as read on the scale.

If it read 10.5 would call out 10.5 if it read 6.25 I would call out 6.25. I would never call out the units in this scenario. In a verbal world the less the amount of thought required the more accurate the transfer of information. In your scenario I think this would apply and work best.

 

[flamby]

IRstuff,
However you like millimeters, I bet you are using a centimeter scale.
After 10mm, the mark will increment by 1, not 10.

toolmantwo,
If your question is which one is popular then it is mm. But if you say which is correct, well, both of them. We use mm, as IRStuff does, but our scales are in cm.

I hope I am not adding to the confusion.

 

[IRstuff]

10,20,30,40,50, etc. with LARGE "MM" etched at the start of the scale

TTFN

 

[enginebob]

Just use millimeters. On metric drawings in the US it is always given as millimeters.
Anything else is confusing like has been pointed out with your 10.5 centimeters deal. Remember there's 10 millimeters in each centimeter.
That .5 represented one half of a decimeter.

 

[RiBeneke]

In most places, the correct metric abbreviation for millimetre is mm (in lower case). This is important. For example Mm is the abbreviation for megametre (10E6 metres).

In your first post, Toolmantwo, you mentioned dividing your centimetre scale into half centimetres (5mm) and then into quarter centimetres (2.5 mm). This was the English way using 1/2 inch 1/4 inch etc, but it is not generally correct for metric scales. The ratios used should be in steps of 5 : 2 : 1 thus the markings would be firstly 10 mm, if this is too large then 5 mm, then 2 mm then 1 mm etc.

Most money coinage systems these days also work with these ratios.