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. See 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.
