On Sat, 02 Mar 2013 15:11:34 -0500, wrote:

On Sat, 02 Mar 2013 07:29:27 -0800, Pilgrim
wrote:


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Thanks for your informative reply. What are the thread specs? Std NPT or
something else. The couplings I have seen for GRC seen to be non tapered.
Is GRC meant to be liquid tight to prevent moisture entering?
Thanks

CP
GRC uses a NPS thread, not NPT (National Pipe Straight) not (National
Pipe Tapered)

I think this misunderstanding has been repeated here several times.
The threads on the ends of rigid conduit are tapered pipe threads.
Female threads on conduit fittings are often straight threads.

Per Wheatland:
"Wheatland’s Galvanized steel Rigid Metal Conduit
(RMC) is manufactured in accordance with the latest
specifications and standards of ANSI® C80.1, UL-6,
and federal specification WW-C-581. The pitch of
RMC threads conforms to the American National
Standard for Pipe Threads, General Purpose (Inch),
ANSI/ASME B1.20.1. The taper of threads is 3/4 inch
per foot (1 in 16). "

From NFPA 70 - 2008:
"344.28 Reaming and Threading. All cut ends shall be
reamed or otherwise finished to remove rough edges.
Where conduit is threaded in the field, a standard cutting
die with a 1 in 16taper (3/4-in. taper per foot) shall be used.
FPN: See ANSI/ASME B.1.20.1-1983, Standard for Pipe
Threads, General Purpose (Inch)."

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Ned Simmons