Internal O-ring Groove in Small Bore

[Jimsehr]

You should check out quad - o’rings.

 

[Jimsehr]

Thank you all for the suggestions! Going in order here:



There are actually two seals: the piston itself and an additional seal between the piston shaft and the body of the pen (which has the small bore in question). The piston seal is intentionally leaky in one direction due to how the ink filling mechanism is designed (see: vacuum filler pens), so the shaft seal is necessary as well, as ink can make it past the piston head. Long story short: the o-ring has to be retained in the bore instead of the shaft.

I did consider a backing piece as you mention, but I wasn't sure how reliable a seal that would be. I'll keep it as an option!


Looks like I didn't search hard enough... I'll keep this one in mind.


Thank you for this resource, very helpful.


The o-ring I have on hand is McMaster P/N 9452K13: 0.101" ID and 0.241" OD. The page I'm looking at has o-rings down to 29 thou ID -- very cute.


Given all the advice on grinding my own part, I think that's the first option I'll try out. Seems like the most satisfying. I'll report back!

Baumium the poster says the O-ring he has is 0.101 ID and 0.241 OD O-ring.
How is he going to get a 0.241 OD into a 0.100 bore ?

 

[eotrfish]

Baumium the poster says the O-ring he has is 0.101 ID and 0.241 OD O-ring.
How is he going to get a 0.241 OD into a 0.100 bore ?

He isn’t. 0.070 cross section x 2 is .040 more than the bore ID.

 

[Baumium]

Touché... thank you for pointing that out before I wasted a bunch of time.
Seems like the best solution mentioned then is to make a seat for the o-ring and a part that backs up against it.

 

[Jimsehr]

Touché... thank you for pointing that out before I wasted a bunch of time.
Seems like the best solution mentioned then is to make a seat for the o-ring and a part that backs up against it.

I’m surprised no one else pointed this out. Maybe my 70 years of experience
Helped me out.
Jim Sehr