[sdiy] Metric OT rant

Steve Begin Steve.Begin at pwgsc.gc.ca
Tue Aug 13 14:43:39 CEST 2002

Then there is Canada, where people use the terms miles and kilometers interchangeably and choose which system to measure by depending on our moods.

> Steve Begin

-----Original Message-----
From: Simon Gatrall [mailto:gatrall at pacbell.net]
Sent: Saturday, August 10, 2002 3:34 PM
To: synth-diy at dropmix.xs4all.nl
Subject: Re: [sdiy] Metric OT rant

>Andre Majorel wrote:
>>  A bit of googling will surely give you the details of the DIN
>>  specs. That's what I used a few days ago to find out what those
>>  obscure US screw sizes mean. I'm pleased to know that a #10 screw
>>  is 4.83 mm in diameter. :-)
>HA ! now if I could only learn the difference between an M5 and an M8
>screw.   :^P
>Seriously... we get to think in a system.  For me, the 4-40, 6-32, 8-32, and
>are easy to regognize on sight and  I could tell you right off what size tap
>drill, etc.
>For metric, even after I multiply by .03937... I still don't know shit.

Obviously not.  0.03937 isn't the exact conversion.  You should 
always use 25.4mm=1" as your conversion factor.  It's easier to 
remember too.

The series of screws that you list is a common one, but it is a mix 
of course and fine thread!  Metric screws diameters are so much 
easier to remember (ie can you count?) and there is one standard 
pitch for each of the smaller sizes.

>I think the Metric system for science makes all the sense in the world...
>by 10 etc...

I understand that it is kind of a pain to have two sets of taps etc. 
in order to deal with both systems, but you know what?  The rest of 
the world (ie not the US) has to deal with the same schizophrenia 
because the "English" system is so pervasive.  If you look at any 
reasonably complex product out there it will have both metric and 
English parts in it.  The only bicycles that I know of that are all 
metric are French.  Cars are a nightmare.  Computers are a mish-mash 
too.  We talk about 2.5" hard drives (the nominal width) and then the 
height is in millimeters and sometimes the mounting screws are 6-32 
and sometimes they're M3!

I have been doing mechanical design for the last 12 years (in the US) 
and I have to say that once you get used to it, the metric system is 
much nicer to work in.    Any real engineer, machinist or tooler 
worldwide will be able to deal with either system, but ultimately it 
only makes sense for everyone to use the same system.  Look at the 
panoply of incompatible modular systems...
Simon Gatrall
gatrall at pacbell.net

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