DECIMALISATION

[Stanley]

DECIMALISATION

28 February 2006

This hoary old topic has raised its head again in the UK. The government has decided to have a meddle in how we measure things again. For some reason which escapes most of us, the use in common parlance of pints and miles is going to do irreparable damage to our ability to compete in the world.
I couldn’t care less actually because I can manage in either system but what really gets up my nose is proponents of metrication saying that their system is rational. There was a programme on R4 today about it and a tailor rang in to point out that for some technical reason that I didn’t quite understand, it is necessary to use a system based on the number eight when altering the size of garments. His argument was that using Imperial all you did was scale by using halves, quarters, eighths and sixteenths of an inch which made it dead simple. The only answer the lady from the Metrication authority could come up with was “Well, how do French tailors manage?” She had completely missed the point that there are certain practical applications where the Imperial system is brilliant. There was a well-understood relationship between 240 pennies to the pound Sterling and the system of weights and measures we used. 12 is a very useful number, far more so in fact than 10 and this was why it was used.
For instance, try calculating a third of a metre. The yard is easy, it’s a foot and because the foot is divided into 12 inches, it is just as easy to calculate a quarter, it’s nine inches. A third of an old Pound sterling is 80 pennies, 6 shillings and eight pence, what used to be called a Mark. You can’t divide the new pound like this.
My biggest beef against the decimal point is its inaccuracy. I can hear the sharp intake of breath but hold on a minute. What is a third in metric? It can’t be expressed accurately, it, and all divisions by odd numbers, results in an infinite number, it can never achieve accuracy. The vulgar fraction, an integral part of the Imperial System is one third, dead accurate. The argument of the Metrication lobby is that this is nit-picking, it’s near enough for all practical purposes. This is rather like the tailors bone of contention about the eight seams in a garment, it all depends what you are doing and the reason why the advocates of metrication see no problem is that they are not omniscient. They have never been asked to make a gear wheel with 127 teeth in it.
A 127 tooth gear wheel is a very common requirement in machining, especially when producing non-standard threads. Try dividing a circle into 127 equal parts using the decimal system, it can’t be done accurately, using vulgar fractions it’s easy. The same applies to any other number of teeth. It just so happens that the requirement for a 127 tooth wheel on an imperial lathe is to convert to metric threads so the metricationists will say that if the lead screw was a metric thread it wouldn’t be needed. Tell that to someone manufacturing for export to the USA where Imperial is still used. Tell it to someone making gearboxes where a certain ratio is needed which requires a gear with an odd number of teeth. Tell it to a millwright who wants to put a hunting tooth in one gear in a pair of bevels to equalise wear during service. You can’t make a gear wheel with a decimal point in the number of teeth. These are all practical problems where the ability to accurately calculate odd numbers is essential. A gear doesn’t recognise ‘near enough’ but the metrication board know nothing about this so it isn’t important to them.
There was another interesting contribution to the debate on R4 this morning, the carpenter who raised the fact that because of its divisibility by odd or even numbers, the inch and the foot were ideal measurements. He had worked in Norway and said that over there the timber was measured in thumbs and fathoms. Globalisation?
One illustrative story for you. In the days when my beard was black I had the job of demolishing a Scheduled Ancient Monument because it had been vandalised beyond repair. One of the requirements of the Permission was that we needed a measured drawing of the monument. This was Dee Mill engine house and I got my architect Peter Dawson to do the survey. He asked me whether we wanted the survey in Imperial or Metric, I said Imperial because that was how it was built. He did the survey and I helped him measure it. As we got into the process he pointed out to me that the unit of measurement the old architect had employed was three inches. With almost no exceptions, every measurement in the house was a multiple of three inches, even the positioning of the holding down bolts for the engine. After he had combined all the measurements and produced the drawings he told me that one thing he had learned from experience was that the acid test of a survey, and incidentally of the original architect’s skill, came when all the measurements were combined in the finished drawing. If the original build and the survey were both accurate, the combined measurements equalled the overall measured values, Dee was perfect. Would it have been more accurate in Metric values?
One last advantage of the Imperial System which has never been recognised is that despite the archaic measures used, it was very easy to grasp the relationships between money, weight and length and do mental calculations. We were all taught this and the short cuts that could be used. Simple ones were that £s per ton was shillings a hundredweight and threepences per quarter. Shillings per yard was pence per three inches. A shilling could be divided easily by four and so there was a relationship between pounds weight and the money. Of course this could be true of metric measure as well but my point is that because we had clearly named and distinguishable units, somehow the mental calculation was natural. How many children are taught mental arithmetic now?
Enough of this ranting, I shall carry on using my Imperial lathes, my vulgar fractions and my foot-rule divided in sixteenths and twelfths. My gear teeth will be perfectly equidistant! Time to get back to some editing and writing. (All done in Imperial measurements of course.)

28 February 2006

[Gloria]

Very interesting Stanley

[Stanley]