O´ring size for SAE 1/4 thread

[Alberto-sp]

Hello.

I have a vacuum meter and it has a 1/4 SAE male thread. It needs a o´ring in the base of the female fitting, but I can´t find the dimensions of that O´ring. I really looked up on the internet, but I get lost with this type of threads, in some places don´t speak about the size of the thread but about of the size of the pipe.

This is the thread. The manual says 1/4 SAE. The flange is 45 degree



At least I need the OD and ID or the OD and CS or ID and CS


Thank you

best regards

 

[extropic]

The 45° SAE fittings do not require an O-ring. They seal on the 45° flare. Take a look at the McMaster link below. It sounds like you need some 1/4" copper tubing, the proper nut and a 45° flaring tool.

McMaster-Carr

McMaster-Carr is the complete source for your plant with over 595,000 products. 98% of products ordered ship from stock and deliver same or next day.

www.mcmaster.com

 

[toprecyler]

Here is info from paper I have at work. If the thread is 7/16”-20 TPI, it should seal on the 45° end, no oring needed like mentioned before.

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[Janderso]

Here is info from paper I have at work. If the thread is 7/16”-20 TPI, it should seal on the 45° end, no oring needed like mentioned before.

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Good job!
I thought I could help, never occurred to me no o-ring was required.
I went straight to the bible to look for o-ring tolerances.
Couldn’t even find o-ring.

 

[Alberto-sp]

Mmm but this one really need it. I´m not using copper but stainless steel. Lets say it is 37 degree, what O´ring woul it need?

Thank you

 

[extropic]

37° flare fittings don't use O-rings either.

Often, photos are not adequate to resolve the angle of a flare cone, but in this case I'm confident it's a 45° cone.
What ever you're constructing, it seems you have decided not to follow a standard.
Since You're not following a standard, just measure the diameter of the fitting where you want the O-ring to sit and chose an O-ring cross section that you think will work . If you still need help selecting an actual O-ring specification, please reply with the dimensions I asked for and any chemical compatibility requirements you think might be germane.

 

[ChazzC]

Casting my mind back to the early 70’s: I was peripherally involved with fabricating a small high vacuum reactor that was made of some exotic SS with 37 degree fittings to connect with SS tubing: no O-Rings (which would have contaminated the process), just metal-to-metal.

 

[toprecyler]

Looking at the fitting with the measurements you have in the picture, I probably would choose #109 size. 5/16” IDx 1/2”ODx 3/32” cross section.


I think 1/16” cross section will be too small, but might also work. Still go with the 5/16” ID size. That Oring number is 011.

These are oring numbers from Hercules sealing products catalog.

I would think you would be ok with standard cheap ORings, from your original post saying it’s for a vacuum meter. But depending on what you are pulling a vacuum on, it may harm certain orings.

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[Alberto-sp]

Thanks for your answers.

I have tried OD 10mm ID 6 mm and works perfect in vacuum. I wanted to know it there was a standar size for that, but whith these dimensions works fine

I know this is not the correct way to do it, but in this set up both threads are made of stainlees and they doesn´t have a good seat.

 

[Iceberg86300]

You have 3ish general options:

If it's a permanent connection between adapters & there are wrench flats on both male & female halves, crush type gaskets work well:

Plain Jane:
Parker Hannifin 2GF-4-pk10 Flare Gasket, 45 Degree Copper Flare Fitting, 1/4" Tube Size (Pack of 10) https://a.co/d/gaV3IV7

Fancier:
Tube Fittings, Copper, for 1/4" Tube OD

McMaster-Carr

McMaster-Carr is the complete source for your plant with over 595,000 products. 98% of products ordered ship from stock and deliver same or next day.

www.mcmaster.com

If the working fluid is compatible then fancier + loktite are friggin awesome for a solid & robust seal, especially in high vibration environments:
Tube Fittings, Threadlocker-Coated Copper, for 1/4" Tube OD

McMaster-Carr

McMaster-Carr is the complete source for your plant with over 595,000 products. 98% of products ordered ship from stock and deliver same or next day.

www.mcmaster.com

For transient connections, especially using knurled style quick couplers meant for fingers instead of wrenches, you're pretty much looking for service related HVAC fittings. California's heat wave got me reacquainted with these options but unfortunately, I can't provide measurements for the true o-rings b/c my spares are gone & the manufacturers of quick seal caps/fittings seem to be deathly allergic to comprehensive documentation.

Anyway, here are true o-rings for 1/4" SAE 45° "quick seal" caps/fittings (quick seal & quick coupler are kinda like Kleenex, you can find the same stuff from all the big names in HVAC in addition to the wildly named Chinese drop shippers):

Robinair (18180) Replacement O-Rings - Pack of 6 https://a.co/d/4xrA8Xm

Or if you happen to be using any hoses with quick coupler style fittings (basically 99% of all common refrigerant agnostic charging/vacuum/manifold/gauge sets available today use quick couplers based on 1/4" SAE 45° flares, which necessarily have to perform well under vacuum):

YuGtcen 120pcs A/C Sealing O Ring Kit Replacement Rubber Gasket Seals 1/4" Thread Fit for R22 (120 pcs, Green) https://a.co/d/5ayq5Pd

Last but not least, NAPA usually has a pretty good selection of o-rings behind the counter, so you can bring in your stuff & maybe find something that will work. Some Ace Hardware stores have a pretty good selection as well.

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