Re: [CAD_CAM_EDM_DRO] Conversion

On Fri Jun 21 10:23:21 2002, Jon Elson, <elson@...> wrote:

>James Owens wrote:
>
>> Hi,
>>
>> I'm working on a DRO and am having some confusion over the conversion of
>> metric units to inches and back again. The device should be able to read
>> glass scales down to 0.001mm or 1 micron so it is important to get this
>> right.
>>
>> I have always used 1" = 25.4 mm but on trying to work it out with a little
>> more accuracy I find that an English mile = 1.609 kilometres or 1" =
>> 25.39457071 mm. but this figure changes depending on who it is coming from.
>>
>> Does the list have any opinions on this.
>
>EMC uses the conversion factor 0.03937007874016, which is the dimension
>of a mm in inches. (Or, multiply by 1000 and you get the size of a meter,
>which is 39.37.... inches.) Since this software was written by NIST, it is
>essentially a "tracable standard", as they ought to be THE authority!
>
>FORGET those miles, trying to convert inches to mm through miles is going
>to get you in big trouble, I'm sure. Us common folk almost certainly have no
>idea exactly how many inches or feet are in a statute mile. Land surveyors
>probably are taught that in school, depending on how messy it really is, I
>don;t know whether they remember it or not. (In practical terms, they can't
>really use it, anyway, as everything is goofed up by the earth's curvature.)
>
>Jon


It depends upon when you _weren't_, "educated", by the Public Fool System.

One Mile = 1,000 Paces for a Roman Legionair = 5,280 Feet = 63,360 Inches.

Bill


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