Identifying THREAD size ?

[anlauto]

Can someone explain how I determine the thread size of these two fittings ?
These two fittings are from a Chrysler power steering box. I want to convert both the hoses to 6AN size but I need to buy the correct fitting adaptors.
How do I measure the thread size, and it's not "pipe thread" correct ?

@Brads70 ? Anybody ?

[Rich G.]

Would the thread gauge that usually comes in a good tap and die set work?

[Burdar]

Rockauto sells those fittings.  Maybe they list the thread specs in there description?

[Brads70]

Its a hyd fitting straight thread no taper. 7/17-20 or 1/2-20 ? Not sure , not pipe tap though. I went to the local hyd line supplier and got the fittings and crush washer but that was years ago , can't remember the exact size?

[anlauto]

I have the two fittings pictured above, but I want to swap them out for 6AN fitting adaptors, that's why I'm trying to figure out their size..

Do I just measure across ? One measures 1/2", the other 5/8"...So is it the same thread as a 1/2" bolt ? 1/2"-20 ?

[Mopar5]

 You could try calling Summit looks like they have some fittings

[jamesroney]

Hi Alan,

The short answer is "yes" the threads are generally the same as an SAE class 2 UNF thread.  As someone said above...they are straight thread, and the small one is 1/2 x 20 TPI, and I think the larger one is 5/8 x 18 TPI.

Definitely NOT pipe thread!

The problem with identifying the threads is that you need more info to define the fitting.  The industrial fitting world uses horrible nomenclature to describe their products.  There are numerous standards, and they don't translate well.

For example, you said you wanted -6AN, which is an Army-Navy designation for the VERY similar 3/8 inch, 37 degree flared JIC fitting. (yes, AN is Army-Navy...even though it has become Air Force / Navy...but the fitting pre-dates the separation of the Army Air Corps to the Air Force)  It is rare to find an AN fitting in the automotive aftermarket, because they almost all use JIC...the only difference being the thread fit.  AN is class 3, JIC is class 2.  But I understood what you meant.

THIS IS WRONG... see the next post.  (((Anyway, the smaller fitting seats on the 45 degree beveled edge near the hole.  The larger fitting seats on the 45 degree chamfer near the hex.  Both of these types of seated))) fittings have unique names in the industrial fitting language.  For ease of communication, the automotive aftermarket calls them things like "chrysler power steering 1/2-20" and "chrysler power steering return fitting" The name describes the application...not the fitting itself.  You've helped me a ton in the past.  I'll see if I can find a supplier and a part number for you.

[anlauto]

In the "world of speed equipment" the term AN is always used when describing the high pressure line fittings...That's the only reason I used the term 6AN.

I checked on SUMMIT and if I can confirm that the Chrysler box is indeed 1/2"-20 and 5/8"-18, then the adaptors I need seem pretty simple to find even though they seem to all be "Inverted Flare end", which I'm not sure will be a problem  https://www.summitracing.com/parts/rus-640380

[jamesroney]

Hi, yes. I wasn't being critical.  I was just pointing out that we all use "common" terms.

ANYWAY, I went to the shop and pulled two fittings from a stone stock 1970 Challenger.  The fittings are NOT seated on the Flare.  Both fittings use copper compression washers like a banjo fitting.  The Summit flared fittings are not generally compatible with the compression washer seats.

I did confirm 5/8-18, and 1/2-20.
Pressure port is 5/16 SAE 45 degree male flare. (also 1/2-20)

But there was another surprise.  My return fitting contains a pressure regulator spring.  Does your application use that?

[anlauto]

WOW...Can not begin to thank you enough 

I do have the spring...I'm now just wondering if using the fitting that has the inverted flare end will matter ? If it doesn't bottom out internally, I could still use the copper washers  and reinstall the pressure regulator spring  I could even file off the inverted flare end to make it somewhat flat.

Here's the ones I'm looking at: https://www.summitracing.com/parts/sum-220667b  and https://www.summitracing.com/parts/sum-220668b

[jamesroney]

Nice find.

220668b looks good for the pressure port side.  I don't like that it is aluminum, but it should work fine.

220667b for the return side should be OK...but you are going to have to machine the backside for the spring.  I don't know how much meat will be left when you bore the ID, and I don't know how critical the depth needs to be.  The good news is that it doesn't carry any pressure so it just needs to not leak.

I assume that you have the tools to machine the fitting.  If not, you can drop ship the fitting to me, and I can machine it for you.  It won't take more than a few minutes in the lathe.  No charge.

James.

[anlauto]

James, you've certainly given me a lot to think about, thank you

[YellowThumper]

Ran into this same issue years ago when converting to hydroboost. Ended up having custom parts turned up by a local guy. Who unfortunately retired. Should have made more sets.
Great info @jamesroney