RE: Canadian Prices (Frank Sprongl)

[Warren Rheaume <RheaW@foster.com>]

Better to use the carpenters' rule: "Measure with a micrometer, mark
with a crayon, cut with an axe."  Or was it the other way around...?

Warren Rheaume

>----------
>From: 	Glenn Lawton[SMTP:lawtonglenn@gsmai.com]
>Sent: 	Wednesday, November 13, 1996 10:43 AM
>To: 	Robert Myers
>Cc: 	Quattro list
>Subject: 	Re: Canadian Prices (Frank Sprongl)
>
>Robert Myers wrote:
>> ...Back when I usta grade stoont lab reports (otherwise known as
>> science fiction) these calculation results would be marked -2 each as sig.
>> fig. errors.  :-)
>> 
>> >
>> >Please pardon the unneccessary precision, but back from my days
>> >as an optics engineer, when such precision mattered:
>> >
>> > 1 m   =       39.37007800 in
>
>
>Thanks for the :-), as I know you are only poking me in a playful way,
>and I already pre apologized for the unneccessary precision, but these
>insignificant figure are sometimes significant, for example:
>
>If my drawing said that the lens or mirror I was making had one feature
>that was 0.1 meter from another, and I told my diamond turning machine to 
>move 3.937000 (it has 1 micro inch resolution), then it would be
>in the wrong place by 7.8 microinches.
>
>Since we regularly used HeNe (632.8nm) laser interferometers to measure
>how accurately we made a part, and often had to meet figure tolerances
>of 1/4 wave, and since 632.8nm/4 = 6.2 microinches, 7.8 is too much! :-)
>
>Glenn
>