From: Rick Merrill
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Subject: Re: what is 100R mean in a schematics?
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NNTP-Posting-Date: Tue, 24 Dec 2002 02:13:37 GMT
Organization: AT&T Broadband
Date: Tue, 24 Dec 2002 02:13:37 GMT
William Meyer wrote:
> Lewin A.R.W. Edwards wrote:
>>I read a diatribe pro-avoirdupois, slamming metric measurements, in
>>one of the EE journals just last month.. I think it was EDN? It's in
>>the trash now, I'm not hunting. I can't understand the attitude. Of
>>course, this gentleman probably expects to go to the supermarket and
>>buy a few drachms of allspice, a gross-nip of milk, a 1/8th-rood roll
>>of cling film, etc.
> By now, I suspect most Americans are reasonably at ease with metric measures, where they find them.
Ah ha! I have a horror story: I'm working on this co-linear robotic arm for
machine tools and they tell me it's a 5 pitch screw and the original code
(that didn't work) had "linear_pitch=5" so I let it be. But the system was
never accurate over large distances. finally I measured diameters,
counted gear teeth and then put
a vernier caliper to the lead screw: it had a pitch of 5.0746 (my measure)
per inch! It turns out to be a metric screw with a pitch of "5" , 5 mm
per thread that is! So linear_pitch = 5.08 and now i'm right on the mark!
There seems to be little incentive to make a wholesale conversion of systems.
> One thing that galls me is the increasing appearance of mechanical products that contain threaded fasters of both Imperial and metric forms. I suspect that the metric fasteners have been used as an alternative to American fine pitch. It just makes it a PITA, having two sets of wrenches in play on a single product.