Today's Message Index:
----------------------
1. 01:13 PM - Re: weepy fuel header tank fitting, CJ6A (Justin Drafts)
2. 04:15 PM - Re: Re: weepy fuel header tank fitting, CJ6A. Attn: Justin Drafts (W LANNON)
3. 05:32 PM - Re: Re: weepy fuel header tank fitting, CJ6A. Attn: Justin Drafts (Robert Graves)
Message 1
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| Subject: | RE: weepy fuel header tank fitting, CJ6A |
Ok CJ6 maintenance experts, I please need some advice.
It's time to resolve my fuel header tank's weep from its forward fitting.
(A chronic CJ6 problem, I understand?)
Removing the original Chinese fitting, I see the threads in tank & fitting
have been scored. I'll try to tap new threads in the tank, but... what size
threads are these? (Pls see the 2 pix, the new fitting next to the old one
for ref.)
Ie- what size tap to use? And where to find?
Advice?
Thanks all, any advice much appreciated-
Justin Drafts
N280NC @ Paine Field WA
Message 2
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| Subject: | Re: RE: weepy fuel header tank fitting, CJ6A. Attn: Justin |
Drafts
Hi Justin;
Don't even think about re-tapping these threads.
What you (and probably most CJ owners) need is at least a basic understanding of
Pipe Thread. Pipe thread was developed by the British in the early days of steam
power. It is a British Standard unilaterally adopted by the rest of the world.
The US of course made some minor changes and re-issued it as a US Standard
as well.
There are two distinctly different versions of Pipe Thread both of which are clearly
shown in your photo. The size designation is based on the O.D. of the pipe
(or tubing) that the fittings enclose. In this case there is no such pipe or
tubing but if there were it would probably be referred to as 5/16" or 3/8" (I
am at home so do not have one to measure). In any case the Chinese designation
system is probably quite different.
If you take a close look at the two fittings you will notice the thread on the
upper one is tapered and the lower one is straight!
Let's call these 3/8" fittings. The upper one would then be a 3/8" NPT (National
Pipe Taper) and the lower one a 3/8" NPS (National Pipe Straight). They are
not interchangeable.
NPT is probably the most common since, when installed in the correspondingly tapered
hole it is reliably self-sealing. If it were NPS to NPS the joint would
require a sealing washer.
What you have shown here is an NPS fitting installed in an NPT hole. Leakage is
guaranteed! I am sure you are not alone.
Best regards;
Walt
From: "Justin Drafts" <draftsjust417@gmail.com>
Sent: Wednesday, June 14, 2023 1:13:06 PM
Subject: Yak-List: RE: weepy fuel header tank fitting, CJ6A
Ok CJ6 maintenance experts, I please need some advice.
It's time to resolve my fuel header tank's weep from its forward fitting. (A chronic
CJ6 problem, I understand?)
Removing the original Chinese fitting, I see the threads in tank & fitting have
been scored. I'll try to tap new threads in the tank, but... what size threads
are these? (Pls see the 2 pix, the new fitting next to the old one for ref.)
Ie- what size tap to use? And where to find?
Advice?
Thanks all, any advice much appreciated-
Justin Drafts
N280NC @ Paine Field WA
Message 3
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| Subject: | Re: RE: weepy fuel header tank fitting, CJ6A. Attn: Justin |
Drafts
Thanks for the explanation Walt. Haven=99t heard from you in a long ti
me. Hope you=99re doing well.
Sent from my iPhone
> On Jun 14, 2023, at 7:17 PM, W LANNON <wlannon@shaw.ca> wrote:
>
> =EF=BB
> Hi Justin;
>
> Don't even think about re-tapping these threads.
>
> What you (and probably most CJ owners) need is at least a basic understand
ing of Pipe Thread. Pipe thread was developed by the British in the early d
ays of steam power. It is a British Standard unilaterally adopted by the re
st of the world. The US of course made some minor changes and re-issued it a
s a US Standard as well.
>
> There are two distinctly different versions of Pipe Thread both of which a
re clearly shown in your photo. The size designation is based on the O.D. o
f the pipe (or tubing) that the fittings enclose. In this case there is no s
uch pipe or tubing but if there were it would probably be referred to as 5/1
6" or 3/8" (I am at home so do not have one to measure). In any case the Ch
inese designation system is probably quite different.
>
> If you take a close look at the two fittings you will notice the thread on
the upper one is tapered and the lower one is straight!
>
> Let's call these 3/8" fittings. The upper one would then be a 3/8" NPT (
National Pipe Taper) and the lower one a 3/8" NPS (National Pipe Straight).
They are not interchangeable.
>
> NPT is probably the most common since, when installed in the corresponding
ly tapered hole it is reliably self-sealing. If it were NPS to NPS the joi
nt would require a sealing washer.
>
> What you have shown here is an NPS fitting installed in an NPT hole. Leak
age is guaranteed! I am sure you are not alone.
>
> Best regards;
> Walt
>
>
>
>
>
>
>
> From: "Justin Drafts" <draftsjust417@gmail.com>
> To: yak-list@matronics.com
> Sent: Wednesday, June 14, 2023 1:13:06 PM
> Subject: Yak-List: RE: weepy fuel header tank fitting, CJ6A
>
> Ok CJ6 maintenance experts, I please need some advice.
> It's time to resolve my fuel header tank's weep from its forward fitting. (
A chronic CJ6 problem, I understand?)
> Removing the original Chinese fitting, I see the threads in tank & fitting
have been scored. I'll try to tap new threads in the tank, but... what size
threads are these? (Pls see the 2 pix, the new fitting next to the old one f
or ref.)
> Ie- what size tap to use? And where to find?
> Advice?
>
> Thanks all, any advice much appreciated-
> Justin Drafts
> N280NC @ Paine Field WA
>
> <header tank fitting 2 (N280NC).jpg>
> <header tank fitting 3 (N280NC).jpg>
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