Re: [AMMRL] Helium ferrule O-ring sizes

From: David Richardson via groups.io <david.richardson=ucf.edu_at_groups.io>
Date: Tue, 06 Jan 2026 10:33:25 -0800

Hi John,

From the numbers you indicated, it appears you have the info you need for
the 5/8 and 3/8. The 114 and 012 (respectively) should be the dash numbers
which correspond to standard o-ring sizes. For example:

Dash 114:
https://www.mcmaster.com/2418T139

Dash 012:
https://www.mcmaster.com/2418T118

I suspect the 1/2 is something like this (2.5mm wide with a 12mm ID):

https://www.mcmaster.com/1174N503

For what it is worth, I went through a similar process a few years ago and
settled on:

Dash 112:
https://www.mcmaster.com/9452K24 for my 1/2” lines.

And

https://www.mcmaster.com/1174N513 for my 3/8”

A mix of standard dash and metric, like the bags you have. I don’t
recall how/why I ended up there. I have been happy with these sizes and have
not found them to be too small nor had the line slip. I also went with the
softer Buna 50, which I prefer at low temperatures, while your current rings
look to be Buna 70.

Hope that helps.

Regards,

David

David Richardson, Ph.D.
Director, NMR Facility and Cryogenic Services
Office of Research
University of Central Florida
david.richardson_at_ucf.edu ( david.richardson_at_ucf.edu )
407-823-2961
http://sciences.ucf.edu/chemistry/nmr/


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Received on Tue Jan 06 2026 - 10:43:02 MST

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