Pat's last example:
How many 7 1/2 centimetre strips can I cut from 3/4 metre of fabric? with How many 75 millimetre strips can I cut from 750 millimetres of fabric? could easily be recast as How many 7.5 cm strips can I cut from 75 cm of fabric? Now the answer is as evident as when using millimeters, namely, 10. But perhaps the issue has to do with converting the mindset of people who use vulgar fractions all the time (because they use or did use Imperial) and will want to keep using them even when decimal fractions are the only kind you should use in metric. I can see then that the value of "breaking" the vulgar fraction mindset (and even worse the compound units mindset that leads to monstrosities like 1 m 35 cm in place of 1.35 m or 135 cm by analogy with, for example, 3 feet 7 inches) by always using whole numbers (which is what millimeters permit). Thus, this breaking of the old mindset could be what outweighs the possible cumbersomeness or false precision implied by using millimeters in place of centimeters for lengths that are either whole centimeters or a decimal fraction thereof to only a single place (digit). In other words, if you were dealing with a populace that already knew only metric and was comfortable with decimal fractions, you could use centimeters in the garment industry with no problems whatsoever. However, given the Imperial mindset of the current workers, it may be the right thing to do to sweep away all fractions in order to pave the way for smooth metrication even if millimeters seems to be a bit of "overkill". For your consideration ... Ezra ----- Original Message ----- From: "Pat Naughtin" <[email protected]> To: "U.S. Metric Association" <[email protected]> Sent: Saturday, May 29, 2010 4:58:52 AM GMT -08:00 US/Canada Pacific Subject: [USMA:47447] Re: Bespoke tailoring Dear Tom, Sorry for the delay in responding to your email.I have been a little bit busy – and I still am. So to remind you that I am still thinking about the issues you raise, I have extracted this short quote from http://www.metricationmatters.com/docs/centimetresORmillimetres.pdf that seem to me to be relevant inside a textile production company. ## Think about bricklayer's assistants and note that we are not talking about intellectual giants here. These folk had little trouble adjusting to house plans that contained numbers like 22 800 millimetres for the length of a wall. One of the reasons for this, I think, is that the big numbers have given their users four distinct advantages on a building site: 1 You don't have to remember the unit of measurement – it's always a millimetre. 2 There are never any fractions. 3 There are never any decimal points. 4 Calculations are mostly simple, but if they're not, they can — without any conversions — be fed directly into a calculator. Compare this with the issues confronted by a textile worker (say a weaver) who still has to: 5 Remember which unit, or units, of measurement they are currently using. 6 Negotiate halves and maybe quarters and eighths of metres and centimetres. 7 Negotiate thirds of yard for feet; and 36ths of yards for inches. 8 Almost always have decimal points with varying numbers of digits to the right of them. 9 Perform calculations that might involve vulgar or common fractions, mixed numbers, decimal fractions or a combination of all of these. 10 Perform calculations by pen and paper methods, as electronic calculators are not good with fractions. For example, compare: How many 7 1/2 centimetre strips can I cut from 3/4 metre of fabric? with How many 75 millimetre strips can I cut from 750 millimetres of fabric? I know which I'd prefer to do. ## Cheers, Pat Naughtin On 2010/05/28, at 23:13 , Tom Wade wrote: However, as an engineer, I am pretty sure that if the finished clothes are to be sized to the centimeter, the pattern pieces will need to be cut to better than whole centimeter accuracy. Further, the practice is that ALL engineering drawings (at least for things under 100 m) be in millimeters, and I would interpret the pattern as an engineering drawing. To the degree that sub-centimeter accuracy is required in the pattern or cutting, I think that manufacturing in millimeters is preferable to 0.1 cm. The finished product can still be labeled and advertised in whole centimeter sizes. What you say makes perfect sense. From the producer's prospective, it would seem more logical to use mm in the design and cutting, but from the consumer's perspective, cm would be a more logical choice to use in labelling. I believe the choice of prefix comes down to: - A prefix that results in whole numbers is preferable to one that requires the use of decimals. - A prefix that results in smaller whole numbers is preferable to one that results in unnecessarily large numbers, or an unnecessarily exact precision. The first would mean you'd choose 46 mm rather than 4.6 cm, and would mean where a greater precision than 1 cm is required, mm would be the preferred choice (and this would therefore be the case in the majority of applications). The second would mean you'd choose a clothing dimension of 102 cm rather than 1020 mm, or a height of 174 cm rather than 1740 mm *provided* you never need a precision greater than 1 cm. Note the the first guideline would mitigate against choosing 1.02 m or 1.75 m (whole numbers preferable to decimals). Tom Wade 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. S ee http://www.metricationmatters.com for more metrication information, contact Pat at [email protected] or to get the free ' Metrication matters ' newsletter go to: http://www.metricationmatters.com/newsletter to subscribe.
