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Ron, <br>
<br>
The fitting I pulled out has an NPT 1/4-18 on the block side and
what appears to be a BSPP 1/4" on the line side. I bought a 1/4-18
tap and die from NAPA today and did some checking. The die fit on
the fitting very easily and was still easy all the way to the base.
The tap actually went into the block quite easily and then tightened
towards the end of the tap. So the conclusion was there is nothing
wrong with the fitting or the threads in the block. However, when I
inserted the fitting into the block, it would progress about 4
threads before it stopped. I took it out and inserted a 1/4" MIP
brass fitting into the block and it tightened down after about 7
threads. I pulled it out and measured the thread diameter at the
point where it stopped. They were at about the same diameter reading
but were at different depths on the fittings. It turns out my
original fittings has a different taper than the brass fitting as
well as being much thicker at the base end. I am thinking someone
may have used an NPTF thread which gets crushed at insertion, is
very hard to extract, and cannot be used again. This would address
all of the symptoms I experienced while removing the fitting and
trying to reinsert it back into the block. I am going to order a new
fitting and see what happens.<br>
Thanks for doing additional research on it for me.<br>
<br>
Cheers, Terry<br>
<br>
<br>
<div class="moz-cite-prefix">On 7/4/21, 11:02 AM, Ron Fraser wrote:<br>
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<blockquote cite="mid:000e01d770ed$f377e540$da67afc0$@bluefrog.com"
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<p class="MsoNormal"><span style="color:windowtext">Terry<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">
I did some more digging and I find there is a difference in
the number of threads per inch.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">NPTF<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">1/8”
27 threads/ inch<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">¼”
18<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">BSPT<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">1/8”
28 threads/ inch<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">¼”
19<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">So these 2
systems have threads that are not totally compatible or
interchangeable. <o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">I believe
the tubing end of the adaptor is parallel thread.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">The threads
per inch is the same for either system tapered or parallel.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">I would
suggest measuring the part accurately is the only way to
know for sure.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">Ron Fraser<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
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