On Fri, 10 Feb 2012 11:12:29 -0500, "Jim Wilkins"
wrote:


"Ned Simmons" wrote in message
.. .
On Thu, 09 Feb 2012 19:28:51 -0600, Robert Nichols
wrote:

On 02/09/2012 12:13 PM, Jim Wilkins wrote:
"Stanley wrote

Both are tapered, at least the ones I have on hand are. Make sure
what you have, there's a straight series as well. ...
Stan

Outside of hydraulics I've seen straight pipe-sized threads only on
screw-in
water heater elements and shower head adapters.

Electrical conduit & fittings and lamp parts are NPS.

Conduit uses a tapered male thread; female threads on conduit fittings
are generally NPS.
Ned Simmons

I'm fairly sure I've seen both straight and tapered, depending on if it was
indoor or liquid-tight, cast metal or plastic box. The plastic imitation
Sealtite that Lowe's sells uses straight male threads and an O ring. I don't
have other samples handy to check.

I should have qualified my statement with "plumbing" though he's not likely
to use an electrical conduit fitting on the radiator.

jsw


I don't doubt that some fittings, especially those for products other
than rigid conduit, have straight male threads. But tapered threads
are specified for the ends of conduit.

From Wheatland’s website:

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).

And the NEC specifies tapered threads for field threading:

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 in16 taper (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).

--
Ned Simmons