Too hard to intersperse with my e-mail reader. To your last point, I know of no examples of fast (nationwide) centimeter transition. Successful transitions require manufactured goods. All engineering societies specify millimeters (and not centimeters) on drawings and those are used on the shop floor. The question is whether the use of centimeters in non engineering and manufacturing circumstances delays metrication, and whether it should be banned.
Millimeters must be used in many circumstances. At best centimeters may be a suitable alternative in some circumstances. Anyway, until the BIPM withdraws the prefix, some nations will use it, and therefore it must be taught, even if it is not emphasized. I think one difference in our mindsets is whether or not millimeters, centimeters, and meters are different units. They are not, the prefix is merely code or shorthand (both easier to write and to say) for scientific notation scaling the number. This may be an engineering view, not obvious to the general public, but without it, the SI isn't so coherent in computations. I don't feel decimals are a big obstacle in the workplace. Perhaps because we have "always" had decimal currency, perhaps some other reason. In automotive, we don't have enough requirements to work at micrometer levels to change all units on a drawing to whole micrometers; however, that may very well be appropriate for a chip manufacturer. We have used unionized, hourly workers on the shop floor to collect SPC data. They require some training to do the collecting and data-crunching. and I would say "most" workers can be trained, a few can not. I would also admit an SPC specialist should review the charts. The workers can identify some, but not all, out-of-control issues. This is a little off the subject, but it gives me some confidence that decimals are no big deal, at least after a little training. The idea of "some jobs" having drawings in micrometers would NOT work. If nothing else, "standard notes" must be "standard" because no one reads them but one time. You would surely get a part 1000X too large. However, another industry, like ICs, could have a "standard note" that says micrometers. It must be "standard" for a given firm or plant, however. The "rule of 1000" is a hardpoint in net contents declarations (FDA/FTC rules). Although NIST mentions it on the page you cited in your "whole numbers" document, they were explaining net contents labels. In SP330 and/or SP811, they mention it, but they specifically recommend violating it when numbers must be "comparable" in a table or text, or in the case of engineering drawings. It is not absolute, except in the case of net contents. Relative to net contents labels, the US also does not allow cL, dL, daL, or hL or cg, dg, dag, or hg. It does allow cm. Finally, what delays US metrication is not whether the centimeter is in or out. US metrication is delayed because nothing either requires it or forbids Customary. Until something does, metrication will be a mixed bag, with a few areas wanting to metricate and doing so. Conversely, those that don't wish too, won't. I would blame this entirely on politicians and not at all on centimeters. ________________________________ From: Pat Naughtin <[email protected]> To: U.S. Metric Association <[email protected]> Sent: Mon, February 1, 2010 5:11:48 AM Subject: [USMA:46547] Re: Centimeters vs inches Dear John, I have interspersed some notes in red. On 2010/02/01, at 09:36 , John M. Steele wrote: I knew it would have that effect. I prefer to think of myself as consistent rather than predictable – somehow it sounds better! I'm certainly not advocating centimeters ONLY. As an engineer, I fully agree that all professional societies advocate the use of millimeters only on engineering drawings (to at least 99.999 m), and that only they are used in industrial manufacturing. Agreed, this is also my observation. (I disagree that the approach avoids the need for decimal fractions; in automotive, many dimensions are to 0.1 mm and some to 0.01 mm). There is probably a place for a recommendation for some workshops to work on some jobs in micrometres only. This is probably appropriate for tool makers. In these cases, and occasions, you would simply apply the 'Whole number Rule: if the majority of measurements required can be done in whole numbers using micrometres then switch to micrometres for that job. I once worked in a textile mill where it was routine to refer to the diameters of all the different kinds of fibres in micrometres in whole numbers of micrometres. Also, what little I know about Federal construction guidelines (the only metric construction in the US) says they use millimeters in plans. I know nothing of these. However, I think both need to be taught. Why? What purpose does this serve? To my mind all that dual teaching does is to provide occasions for teachers and students to develop two mindsets – one based on millimetres and another - conflicting - one based on centimetres. Last week I tried to read a book called 'Science and the garden : the scientific basis of horticultural practice' edited by David S. Ingram et al, but I found it to be almost unreadable as each measurement reference required me to change my mindset to that of the current contributor as they continuously alternated between metres and fractional metres, centimetres and fractional centimetres, and millimetres (without fractions). Needless to say I would have preferred them to have edited all measurements in their garden plots in millimetres; I would then not have to pause to do a (granted simple to do) calculation each and every time I encountered a number in their text. For measuring people, clothing, plants and animals, snow, etc., millimeter resolution is often excessive, and the practice has been to work to the centimeter. To be accurate in measuring human heights millimetres is probably the best choice. As you know your height varies through each day from the time you first rise from bed until late in the evening; this varies from about 12 mm to as much as 38 mm for adults. To be accurate and precise millimetres should be the preferred unit for measuring height in medical settings. On the subject of clothing the Australian building industry gains a great deal in accuracy by 'aiming' at millimetre precision; I have often thought that this same advantage would also be useful in the textile industry particularly for garment construction. I would probably agree that the centimeter should NEVER be used with a fraction, vulgar or decimal. If an integer centimeter isn't good enough, then centimeters aren't good enough, use millimeters. I agree. However, not all folk have your numerical abilities and understandings; centimetres are routinely used with fractions. I don't know if it is still true but the Apple Macintosh word processor used to arrive with the page layout defaults for centimetres set in halves and quarters of centimetres. Alternatively, I could probably live with no centimeters if the rule of 1000 allowed numbers down to 0.01 m, where the number was limited to two decimal precision. (it's not really a rule anyway, only a guideline) I never did fully understand the so-called 'Rule of 1000', which is why I devised the 'Whole number rule' to replace it. See http://www.metricationmatters.com/docs/WholeNumberRule.pdf I don't think the choice makes or breaks metrication (lack of political will is COMPLETELY effective, however) or that the US particularly tried to adopt the centimeter. I agree that it is not a make or break situation. It is a slowing situation. The choice of millimetres can lead to fast, smooth, and generally complete metric transitions. The choice of centimetres does not. Believe me, I have earnestly searched for an example of a fast metrication transition using centimetres, but I am yet to find one. Perhaps you can direct me to an example that I might study. All metricated industries use the millimeter internally, they may use the centimeter in promotional material, and a few other fields use the centimeter. Thus encouraging the development of dualistic mindsets and reference values both for the company and for all of their intended customers. Cheers, Pat Naughtin Author of the ebook, Metrication Leaders Guide, that you can obtain from http://metricationmatters.com/MetricationLeadersGuideInfo.html PO Box 305 Belmont 3216, Geelong, Australia Phone: 61 3 5241 2008 Metric system consultant, writer, and speaker, Pat Naughtin, has helped thousands of people and hundreds of companies upgrade to the modern metric system smoothly, quickly, and so economically that they now save thousands each year when buying, processing, or selling for their businesses. Pat provides services and resources for many different trades, crafts, and professions for commercial, industrial and government metrication leaders in Asia, Europe, and in the USA. Pat's clients include the Australian Government, Google, NASA, NIST, and the metric associations of Canada, the UK, and the USA. See http://www.metricationmatters.com/ to subscribe. From: [email protected] >To: [email protected] >Subject: [USMA:46533] Re: Centimeters vs inches >Date: Mon, 1 Feb 2010 08:02:07 +1100 > > >On 2010/01/31, at 23:14 , John M. Steele wrote: > >Pat will love this story: >>http://www.newschief.com/article/20100131/NEWS/1315040/1009/LIVING?p=1&tc=pg >> >>Wife measures in inches at home, and in centimeters in store. Great line, "I >>just thought they were small inches." >> >>It ends questioning why we use the ruler of the ruler we overthrew in 1776 >>and advocates the US going metric. > > >Dear John, > > >Great story and well told. > > >However I would like to point out something about my attitude to centimetres. > > >Some years ago I observed that metrication transitions using centimetres went >much more slowly than metrication transitions using millimetres. Transitions >using millimetres were smooth, rapid, and complete while transitions using >centimetres were (and are still) slow, partial, and so riddled with bitter >fighting that they seem to be endless. > > >This puzzled me because I simply didn't understand why this should be so, and >in particular why the difference should be so dramatic. As examples, the >Australian building and construction industries chose to use millimetres for >their metrication transition and they were all done with the process in about >two years; the textile industries chose to use centimetres and they are still >struggling with their metrication transition after 40 years with no clear end >in sight. These were personal observations as I worked in both of these >industries. > > >Sadly, very sadly, our primary (elementary) and high school teachers in >Australia also chose to use the centimetre based approach. We now have the >situation where children leave school to (say) begin a construction job and >they have to begin to learn about how to plan, cut, fix, and estimate using >millimetres. I overheard a discussion between an old carpenter and his new >trainee when the youngster reported a measurement in centimetres; the old man >scornfully commented, 'What's that cm thing, we call cm a "curtain measure" >around here, and we don't ever use them.' > > >I have long been an admirer of the policy of the Australian building industry >for its simplicity and for its clarity. The Australian Building and >Construction Advisory Committee policy was: >The metric units for linear measurement in building and construction will be >the metre (m) and themillimetre (mm), with the kilometre (km) being used where >required. This will apply to all sectors of the industry, and the centimetre >(cm) shall not be used. … the centimetre should not be used in any calculation >and it should never be written down. >*Standards Association of Australia 'Metric Handbook, Metric Conversion in >Building and Construction 1972 >With these words the Australian Building and Construction Advisory Committee >effectively banished centimetres from the building trades in Australia, with >the result that metric conversion in these trades was smooth, rapid, and >completed in about two years. Most other trades followed their example, and >subsequently followed their successful metrication program. Broadly speaking, >about 85 % of Australians work in millimetre based activities; about 10 % use >centimetres; and the remaining 5 % rarely measure at all. >About that time, I decided to investigate this issue and sought the support of >the knowledgeable people who subscribe to the USMA maillist – the long paper >in the form of a discussion >at http://www.metricationmatters.com/docs/centimetresORmillimetres.pdf is the >result of this consultation process. > > >During the years that I have been watching the differences between >centimetre metrication transitions and millimetre metrication transitions I >have formed various views as to why there are such notable differences. As an >example, my first idea, which I have now rejected, was that centimetres were >chosen by occupations traditionally taken by women and that millimetres were >chosen in traditional men's activities. > > >Currently I think that the choice of millimetres has profound advantages over >centimetres because it favors the almost exclusive use of whole numbers within >a work environment – there are no vulgar or common fractions and there are no >decimal fractions on any building sites in Australia because all dimensions >are in millimetres. This is also true for building sites in India, New >Zealand, and South Africa. > > >My goal at the present time is to try to inform people who have not yet made >their choice as to whether to use centimetres or millimetres to choose the >better approach of using millimetres. I believe that the failure of the >metrication process in the USA in the 1970s can largely be traced to the >choice of centimetres because the process worked so slowly that the >participants considered that, after a few years of trying, the entire process >had failed. The truth is that the centimetre based metrication transition >started in the 1970s will now continue until metrication is completed – this >is inevitable once the process has begun – but it will be slow, it will be >costly, and it will be painful. So far, like centimetre based metrication in >Australia, it has taken 40 years and there is no clear end in sight. > > >It's hard to predict how long a centimetre based transition might take, but it >is probably reasonable, as a best guess, to suggest 200 years as a working >figure. The alternative is to choose millimetres and have done with the whole >metrication transition process by about 2012. As a 'Rule of Thumb' you could >think of 2 years for a metrication transition using millimetres and 200 >years for a metrication transition using centimetres. > > >Cheers, > >Pat Naughtin >Author of the ebook, Metrication Leaders Guide, that you can obtain >from http://metricationmatters.com/MetricationLeadersGuideInfo.html >PO Box 305 Belmont 3216, >Geelong, Australia >Phone: 61 3 5241 2008 > > >Metric system consultant, writer, and speaker, Pat Naughtin, has helped >thousands of people and hundreds of companies upgrade to the modern metric >system smoothly, quickly, and so economically that they now save thousands >each year when buying, processing, or selling for their businesses. Pat >provides services and resources for many different trades, crafts, and >professions for commercial, industrial and government metrication leaders in >Asia, Europe, and in the USA. Pat's clients include the Australian Government, >Google, NASA, NIST, and the metric associations of Canada, the UK, and the >USA. See http://www.metricationmatters.com/ to subscribe.
