[time-nuts] Ultra low phase noise floor measurement system forRF devices.
Chuck Harris
cfharris at erols.com
Sun Apr 1 10:35:59 EDT 2007
Didier Juges wrote:
> In France, and I suspect in the rest of the world, machinists talk in
> 1/100th of a mm (centieme in French). The 'centieme' is a very good
> fractional unit when dealing with hardware. It is not harder to talk in
> 1/100th of a mm than in 1/1000th of an inch.
Talking isn't the problem, actually machining to 1/100th of a mm is the problem.
Machinists, and the machines they use, run out of steam around a thousandth of
an inch. 1/100th of a mm is a practical impossibility for a lathe, or milling
machine to achieve. But 1/10th of a mm is too course for operations involving
fit (bearings, press fits, ...). So you end up counting in 4/100ths of a mm,
rather than 1/1000ths of an inch.
Cutting threads is a real nightmare with non CNC metric lathes, but super
easy with non CNC English lathes.
>
> After 33 years in France, and 22 here in the US, I must say I have not
> completely converted, by a long shot. The Imperial system is just too
> ridiculous. It is an offense to common sense. BTU/hr? please spare me :-)
I'm puzzled about why that particular arbitrary constant bothers you.
A BTU is the amount of energy necessary to raise 1 cubic foot of water 1F in
temperature. A BTU/hour takes one hour to raise the temperature of the water.
It is no more, or less, arbitrary than the calorie, but it is a whole lot less
wierd than a calorie/hour, or a kilometer/hour for that matter.
Life will always be a blended system, unless you decide you want a metric day,
metric week, metric year... I don't think that nature will accommodate you very
well.
-Chuck Harris
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