RE: [PipingDesign] Why piping GA are in 1:33 scale?

From: <Richard>
Date: Sun Jan 20 2008 - 15:40:00 EST

Hi L.
In the "old days", in Canada anyway, we used to draw (manual drawings of course) in imperial measurements at a scale of 3/8" to 1'-0", which corresponds to 1:32. I can't speak for the rest of the world, but when Canada went metric in the late 1970's we started drawing at the closest rounded equivalent of 1:30. 1:30 (and 3/8" to 1'-0" before it) has proved to be the most convenient scale to maintain clarity of the detail on a drawing of "A1" metric size or "D" imperial size sheet of paper. 1:50 would mean less drawing sheets, but the smaller detail may be lost. 1:25 means greater detail, but larger items are larger than needed, and results in more drawing sheets.

1:33 is very close to 1:30, so the above applies here also. I have a old scale rule kicking around that has 1:33 1/3 on it. Off the top of my head I can't remember the reason for this, although obviously there is one. Maybe one of the other old timers can remember. I'm going to go dig this scale up. Maybe then I'll remember the rational.

Richard B.
Calgary, Canada

-----Original Message-----
From: [] On Behalf Of Lakshaboopathy Subramanian
Sent: January 20, 2008 12:23 PM
To: PipingDesign
Subject: [PipingDesign] Why piping GA are in 1:33 scale?

Anyone can explain why the piping GA are making in 1:33 scale? we can make it in 1:25 or 1:50. How the odd number 33 came to the picture?

Thanks and regards,

Never miss a thing. Make Yahoo your home page. <> com/r/hs

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Received on Sun Jan 20 15:40:00 2008

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