What thread on the petrol line brass fittings?

[Srenner]

In the May 1952 List of Spares for the Jupiter, these are called out as Item No. 3251, ND392. I think they measure 24 tpi. This same thread is found on the banjo for the carb 3309, 06099. The fittings 3246, 52209 found at the electric SU fuel pump and the gas tank are 1/4 BSP and a much lower tpi. I have searched BA, BSC, BSF, BSP, BSTP, BSW, CEI, UNC, UNF, ME and BSB with nil for my efforts!

Thanks for the assist!
Cheers,
Scott

[Keith Clements]

I will have a check tomorrow but this article suggests it may be M12x1.25, I always thought it was BSP

[Srenner]

Well, 25.4/1.25 works out to a little over 20 tpi, so still too coarse. My 24 thread gauge fits pretty well, and even though it IS slightly suspect having been made by the cheapest bidder in an unnamed Communist country, I reckon it's not that far off. I have my fingers crossed that it's not another Jowett only thread! I mean, the flex fuel line to each carb had to have the matching male part! Surely Jowett didn't make those. What a strange world.

[Keith Clements]

For union nut part ND392- American 1/8" National Pipe Straight27tpi

For filter plug part 06098- Metric 1.25mm pitch gauge fits perfectly -11.47mm male o.d but could be 7/16" UNF. My 20tpi American thread gauge is not as good a fit as the metric one. 20tpi = 1.27mm pitch. But since there is no metric thread standard that fits that I can find , I would go for UNF.

For banjo part 06099- 24 tpi(1.05mm) or 1.0mm pitch, 12.2mm or 31/64" male o.d.

Is it American? The 1/2" UNF is 2O tpi and the 1/2" UNEF is 28tpi, so this is in between!

It could be a BSP thread. British 24 tpi thread gauge seems just as good a fit as does the metric 1.0mm gauge. I cannot see more light coming through with the 5 deg difference in thread form. So subracting .25 inch from .4845" gets about 1/4" which is BSP size. But BSP requires 19 TPI so that is not correct.

So it could be metric 12mmx1.0 and that is a standard.
I am still not convinced.

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[Srenner]

Okay, what a maroon I am. How about we look at COMPRESSION fittings? After all, it is a copper tube with a ferrule and a union. Mmm, 5/16" compression nut. The 5/16" hole fits the 5/16" tubing. Coincidence?!? Say, Mr. Hardware Store Employee, "What thread is a 5/16 compression fitting?" "How would I know" was the answer. Yep, America is a great country. Turns out all sizes are the same 24 tpi so stoopid people can't set their car on fire by mixing parts.

I bought a three-pak (why are they sold in threes?). They fit all the threads EXCEPT the piece I was using as my sample. Can't even get one to start.

To answer my own question, the ever handy, sold in threes, standard 5/16" compression nut. Ferrules old separately.

[PJGD]

I am not sure if the right answer appears here, but I always find that the Maryland Metrics website is a useful resource for this sort of information:

http://www.marylandmetrics.com/tech/tict2011.htm

Philip

[Keith Clements]

Cheer Philip,
Looks like the banjo is designated in table A and then table SD with a pitch of 24 that makes it special use for compression fittings. Could be a challenge getting a tap and die!

[ian Howell]

The brass pipe fittings on my car are - as far as I have checked them, i.e. most of them - BSP (British Standard Pipe), either 1/8" or 1/4"

The fraction bears no resemblance to the size of either the pipe or the fitting threads.

Modern - ie metric - compression fittings are totally different so I'm afraid you might have to rely on sourcing the correct items if you want to match an existing thread.

Of course, if you are simply trying to connect two lengths of imperial pipe then how about a simple 'sleeve' soldered on?

[114]

So far as I can tell the thread looks like 1/2" x 24 TPI UNS
Tracey Tools keep the taps & dies.
Link below


http://www.tracytools.com/taps-and-dies ... 2-x-24-tpi

[114]

This outfit appears to supply the correct 1/2" by 24 tpi 5/16" bore compression fittings

http://www.ebay.co.uk/itm/Enot-Tubing-N ... o_QsbcfZbw