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
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.
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.
