O-ring installation, something to avoid it being a 3 ring circus?

[WobblyHand]

I have to install some NBR90 1.5 x 4mm ID o-rings onto a 6.95mm OD high pressure air probe. I did one NBR70 for a bumper and managed to get it over three grooves, but it wasn't easy at all. The second o-ring, an NBR90, I could barely get it into the first groove, which as a mere 2mm from the end of the probe. I'm having zero luck with the last o-ring, another NBR90. It split on me, when I attempted to stretch it. Is there some sort of trick to install these little stiff o-rings? Help me achieve enlightenment. At the moment I feel like I'm wrestling a greased pig. I need about 6 hands and have 2. The o-ring on the right is NBR70, the other two are supposed to be NBR90. Appreciate any tips. Part is 38mm long, narrow end is 6.95mm, wide end on the right is 7.86mm OD. Right side o-ring is only a bumper, it doesn't seal.

 

[eotrfish]

Make an installation sleeve like this. It should be a slip fit on the piston with the thinnest wall that you can manage.
lubricate the sleeve with silicone grease or Parker O-lube. Warm the o-ring and slide it in place. I've installed hundreds of similar size 90Duro o-rings with a tool like this - works great.

 

[WobblyHand]

Thank you! Interesting, I was designing something similar, save for the really thin sleeve. Not really sure how to make something that thin!
I was thinking of using a pin to locate the unit. I have room in the bottom of the probe to drill a short 2mm diameter hole.

This is about 7 degrees, but the same idea.

 

[extropic]

To create a thin wall cylinder, finish the ID first, then fill the ID with a Gage Pin (or the like) to support the wall as the OD is being turned to size.

 

[ddillman]

loop a small zip tie loosely through the o-ring and walk it down the shaft then cut the zip tie

 

[WobblyHand]

To create a thin wall cylinder, finish the ID first, then fill the ID with a Gage Pin (or the like) to support the wall as the OD id being turned to size.

Thanks for that idea.

Seems like I'm in the ever expanding mode of making tooling to finish my part mode. Wasn't expecting that "simple" o-ring installation would require this kind of stuff. Oh well, suppose it keeps me out of trouble, maybe. Hmm, a 7mm hole is kind of small, have to check to see if I have something that small to bore with. Should have a Micro100 bit that might work.

 

[WobblyHand]

loop a small zip tie loosely through the o-ring and walk it down the shaft then cut the zip tie

That's a better and more rugged idea than using dental floss. I like it.

 

[ddillman]

also try warming in oil

 

[mmcmdl]

lubricate the sleeve with silicone grease or Parker O-lube. Warm the o-ring and slide it in place. I've installed hundreds of similar size 90Duro o-rings with a tool like this - works great.

We had 100s of valves on our fillers that we made up installation tools similar to this one . Worked great and the Parker O ring lube works great also . Had to pull out the trusty pick sets on some of those little SOBs when neccesary also .

 

[WobblyHand]

For the application, I need to use silicone based oil. Petroleum based oils and high pressure air are hazardous.

This will be an interesting project, haven't attempted anything like this before. You all make it sound easy. Somehow hope to muddle through.