On Mon, 14 Jan 2008 05:56:18 +1300, Tom
wrote:

Stealth Pilot wrote:

On Fri, 11 Jan 2008 21:28:50 -0600, "Don Young"
wrote:


Going through some old taps I found a tap marked 1/4"-18. I know that is the
designation for a standard NPT tap but this tap is actually 1/4" in
diameter. Looks like a 1/4"-20 with coarser threads. Does anyone know of an
application for such a thread? I suspect it might have been made mistakenly

from a list of sizes which included the pipe thread. No manufacturer

identification and appears to be a cheap import quality.

Don Young



a 1/4 x 18 straight thread is NPSF (straight) DRYSEAL ...whatever that
means in english. it is a pipe thread.

in a taper that thread would be NPTF (taper) DRYSEAL.


Stealth Pilot

I hope you read you pilot notes with greater concentration than you did the
original post? :-)

Tom
Got me a left hand thread nut off a dead 1/2 inch arbor and decided to
make me an arbor to fit the other end of the 1/4 HP, double shaft
motor. Started to cut the threads when something told me to verify
that I had everything set correctly, oh-oh, I'm cutting 20 tpi and the
nut is 24 tpi. Fortunately I had only done one pass; my arbor has a
funny thread every fifth one.
Gerry :-)}
London, Canada