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CCKW brake pipe union sizes

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Ok guys, I know the two sizes of brake pipe in the chassis on the CCKW's is 1/4" and 5/16" but what about the sizes of unions on the ends of the pipe ?

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Yeah.. that's kinda obvious.

 

TM9-801 has all of 1 sentence regarding tube repair:

 

Para 191(d) Pg 361

d. Tube Repair. Hydraulic tubing may be cut and flared with standard flaring equipment.

 

 

What you want to do is get a copy of the Nov 1944 Army Motors, it has a complete write up on the new brake line routing.

 

Other than being a standard double flare and the needing the proper frame rail T's its all standard stuff. Just be careful that the counter person doesn't give you ISO parts (ie metric) instead of standard fittings.

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1/4 and 5/16 SAE?

 

Little confused here, so if I order 1/4" or 5/16" male unions they will fit over the 1/4" or 5/16" dia tube, how does that work !!!! Do they then send them in a Self Addressed Envelope isnt that what SAE means :blush:

 

Yeah.. that's kinda obvious.

 

TM9-801 has all of 1 sentence regarding tube repair:

 

Para 191(d) Pg 361

d. Tube Repair. Hydraulic tubing may be cut and flared with standard flaring equipment.

 

 

What you want to do is get a copy of the Nov 1944 Army Motors, it has a complete write up on the new brake line routing.

 

Other than being a standard double flare and the needing the proper frame rail T's its all standard stuff. Just be careful that the counter person doesn't give you ISO parts (ie metric) instead of standard fittings.

 

Yep thanks for the info on the tube I have the flaring tools to do the ends and the copper / nickle tube, as I have done the lines in the chassis about 10 yrs ago and still as good as new, but did not know the sizes of the male union ends.

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Society of Automotive Engineers, a U.S. derived association. The SAE thread is also known as AN and was a ww2 universal specification for both Army and Navy (AN).

 

Don't quote me but I think 1/4 pipe fittings use 7/16 SAE threads, and 5/16 pipe fittings use 1/2 SAE.

 

These threads are not common in UK but some manufacturers of fittings do offer them. I found a company (near Northampton I think) who supplied small quantities at very reasonable prices. I reckon Uncle Rex could fix you up if you can't locate a source.

Edited by N.O.S.

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Society of Automotive Engineers, a U.S. derived association. The SAE thread is also known as AN and was a ww2 universal specification for both Army and Navy (AN).

 

 

 

Tony,

I have never heard that AN meant that before. I am certain it stands for American National, as in ANC or ANF (Coarse and Fine).

 

regards, Richard

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I think that you would be best advised to measure the diameters of the nuts and use a thread gauge to establish the tpi. I am currently doing the brakes on a Chev CMP which is piped with 1/4" tube. The male threads on the flexible hoses are 7/16 x 20 tpi, which is UNF, but the female ones are 7/16 x 24 tpi, which my Presto booklet describes as NS-"special threads of American national form". A bit confusing but apparently American practice on many vehicles of that era.

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Richard - you're not the only one! I always related it to National, but discovered these apparently are now only designated ANC or ANF or NPT (National Pipe Thread) and probably a load more!

 

I was also wrong about AN - it is Aeronautical and Navy spec. It seems the U.S. military got together just prior to WW2 and agreed a military spec for pipe threads which is like Unified threads but which provides a tighter fit between threads. The spec they agreed on was based on the old SAE which came about around 1916, based on UNF threads.

 

Wikipedia has much to say on the subject but it isn't all in one place and I suspect some of the info may conflict in places!

 

So the whole lot seems to be interchangeable in a way, being essentially UNF thread rates but with minor variations to the thread form?

 

I suspect any SAE fittings made over here use standard UNF thread profile.

Edited by N.O.S.

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I think that you would be best advised to measure the diameters of the nuts and use a thread gauge to establish the tpi. I am currently doing the brakes on a Chev CMP which is piped with 1/4" tube. The male threads on the flexible hoses are 7/16 x 20 tpi, which is UNF, but the female ones are 7/16 x 24 tpi, which my Presto booklet describes as NS-"special threads of American national form". A bit confusing but apparently American practice on many vehicles of that era.

 

I'm still learning here- no expert - but it seems SAE fittings have different thread pitches depending on the type of fitting.

 

For example a 1/4 pipe compression union would have 7/16 x 24tpi whereas the union for a 45degree flare fitting would be 7/16 x 20tpi.

 

So your CMP flexy hoses may still be SAE fittings (and I think they could also be called JIC).

 

Have I now confused everyone, or just myself???????

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You need to be aware of context. AN relates to aviation and I'm fairly sure stands for Army Navy. AN(F) indeed stands for American National (Fine). The latter was often abbreviated to AN when the size and pitch had already been specified such as 1/2" x 20 AN.

There were a variety of pitches in standard use before US threads became Unified in the 1950's. Most of the common ones were selected for the unified series but not all. 1" ANF was 14 tpi, 1" UNF is 12 tpi, a fact that continues to catch Sherman restorers to this day!

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Richard - you're not the only one! I always related it to National, but discovered these apparently are now only designated ANC or ANF or NPT (National Pipe Thread) and probably a load more!

 

I was also wrong about AN - it is Aeronautical and Navy spec..

 

Thanks Tony,

We are always learning something! Obviously the people who taught me all those years ago thought the same thing :)

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Richard, I spent 30 minutes this morning looking at various 'authoritative' sites outlining the development of U.S. threads and can advise they are quite inconsistent in their descriptions of the origin of these terms.

 

It is a very complex subject which I propose to let pass me by to the extent that I have a supply of the fittings I need :banana: :D

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Some of the fittings on a CCKW are no longer made, or more correctly, are no longer standards in the line/hose/fitting specifications.

 

Plus you have to wonder what is still an original part, what has been swapped after the truck was given to another government, and finally what did the previous owners do to it.

 

So the answer might just be 'all of them' :D

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Curiosity aroused, I have dug out a copy of Machinery’s Handbook of 1944 to learn more about SAE (Society of Automotive Engineers) threads. There were four categories, Course and Fine series, 8, 12 and 16 pitch series, Extra Fine and Special Pitches. Pipe threads, aeronautical screw threads and several other American systems are not covered by the SAE specifications, at least at the time of publication.

The Course and Fine series and 8/12/16 series are similar to American standard threads. The Extra Fine and Special Series are particular to SAE. All types had the same American standard profile.

 

To explain:-

The Course and Fine series are said to be just the same as American Standards threads, which with some modifications later became UNC/UNF.

 

The 8/12/16 series had the same pitch (threads per inch) for different diameters. For instance, the 16 tpi series ranged from ¾ “to 4”dia. and was said to be suitable for adjusting nuts and bearing retaining collars.

 

The Extra Fine series ranged from 1/4” to 6”diameter. As an example a ½”dia. thread has 28tpi.

 

The Special Pitch series is more complex as each diameter has a range of pitches. A ½”dia.thread can be 14,16,18,24,32, or “for special applications”28 tpi. Each category also has a range of up to four manufacturing tolerances, specifying limits to achieve looseness through to tightness for different applications.

 

Until today I thought that our Whitworth based thread system was complicated!! :nut:

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The seal in a hard brake line is make by the tube flare. The fitting is just there to hold things together. So as long the the fitting has the proper threads and flare type it will work... no matter what its called.

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Looks like its almost impossible to match the thread on that pipe fitting ...:undecided:

 

What a job, sorry to give you all late nights researching all those SAE's UNF's, UNC's, AN's and TPI's :cool2: :cool2:

 

Ha, silly me thought it was an easy job.

 

If it rains much more this year, like it did last year I am going to start collecting stamps.................:-D

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Looks like its almost impossible to match the thread on that pipe fitting ...:undecided:

 

What a job, sorry to give you all late nights researching all those SAE's UNF's, UNC's, AN's and TPI's :cool2: :cool2:

 

Ha, silly me thought it was an easy job.

 

If it rains much more this year, like it did last year I am going to start collecting stamps.................:-D

 

I am currently going through the brakes on my son's CMP so the time is not entirely wasted. The job is becoming a something of a war of attrition, buying parts as near as possible to the originals, then making them fit- including brake union nuts!

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Looks like its almost impossible to match the thread on that pipe fitting ...:undecided:

 

 

 

I would strongly recommend you phone Rex Ward he will be able to sort you out either with the original parts or a modern replacement

 

Pete

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Looks like its almost impossible to match the thread on that pipe fitting ...:undecided:

 

What a job, sorry to give you all late nights researching all those SAE's UNF's, UNC's, AN's and TPI's :cool2: :cool2:

 

Ha, silly me thought it was an easy job.

 

If it rains much more this year, like it did last year I am going to start collecting stamps.................:-D

 

 

 

Best of luck with your efforts :) I changed some of my pipes over last year Link, with Rex Ward making them up for me.

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