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Re: [TowerTalk] 2" O.D. Pipe???

To: "Tower and HF antenna construction topics." <>
Subject: Re: [TowerTalk] 2" O.D. Pipe???
From: "Rick Karlquist" <>
Reply-to:, "Tower and HF antenna construction topics." <>
Date: Wed, 17 Mar 2010 16:21:30 -0700
List-post: <">>
Richard M. Gillingham wrote:
> Pipe is measured ID..  TUBING is measured OD.  Try tubing..
> Good luck.
> 73
> Gil, W1RG

No, pipe is measured by OD, but specified by "trade size".

Trade size "1 1/2 inch" pipe has an OD of 1.900 inches.
The ID varies with wall thickness.  Schedule 40 has an
ID that is slightly larger than 1.5 inches and schedule
80 has an ID that is slightly smaller than 1.5 inches.
The ID can also vary depending on what material the pipe
is made from.  Thin wall sprinkler pipe has an ID that is
considerably bigger than 1.5 inches.

Trade size "2 inch" pipe has an OD of 2.375 inches.
Again the ID varies above and below 2 inches.

This is actually good because you know that anything with
1.9 or 2.375 OD is almost certainly water pipe, which
you probably don't want to use for antenna support.

The reason why the OD of pipe is invariant vs wall thickness
is so that they only need one threading system for all
schedules/wall thicknesses, and so that fittings are
interchangeable between schedule 40 and schedule 80 (also
other schedules in PVC).  Also, the OD is held to a very
close tolerance so the fittings fit, whereas the ID has
very loose tolerances and I have found when buying actual
pipe that it indeed varies all over the place and is sometimes
out of tolerance, even though the tolerance is loose.  I have
probably annoyed a number of pipe salesmen by taking a pair of
calipers to their pipes to check ID before buying.

Rick N6RK


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