Sealing surface finish roughness (Ra) for Flat O-ring ?

[Rdpere]

Im making a device which must hold a little less than 1 bar of air pressure.
I have the problem as it is leaking and im not sure why ...
I noticed that where one part is screwed to another (M assembles to the female hole with Flat Oring), there is a little damage because start
of the thread is cutting inside the flatring. But even when i changed the flatring, there is still a leak.

On the drawing the roughnes is defined as Ra =3,2 um ... is this too much?

How important is the finish of surface where the Flat Oring is placed?
Is the note, that there must be no scratches not enough?


Thank you in advance for ANY help or suggestion!

 

[JJPellin]

A drawing would help. What is a flat o-ring? I don't recall every hearing that term.

Johnny Pellin

 

[hydtools]

Does the seal have sufficient squeeze?
Does the seal get damaged when assembled?
Is this a circular seal with a rectangular or square cross-section?
What is the hardness of the seal material?
I would use 1/2 to 1/4 of that surface finish. Does your finish have a spiral texture/lay?

Ted