O-ring installation

[dblcrona]

I have an application where I need to install a 1.5" diameter o-ring on the OD of a threaded end cap. The end cap is about .38" thick and has a recessed area for the o-ring which lies between an external thread and a lip. We currently use aluminum tapered cones with a recess on the large end to install our o-rings. The threaded end of the end cap is inserted into the recess on the tapered cone and the o-ring is pushed over the taper and snaps onto the end cap. This works great and the aluminum can be polished smooth enough that the o-rings do not roll down the taper, they slide down with a light oil. The aluminum is soft though and can get sharp edges if dropped which can damage the o-rings. We tried making the cones from Teflon but it tends to grab the o-rings and roll them. Any tips on a better material or a better way to install external o-rings would be greatly appreciated. Lastly, does it matter if the o-rings roll? Will it affect how they seal if they don't land perfectly right?

 

[MikeHalloran]

I think rolling predisposes o-rings to spiral failure, even if it doesn't overstress them otherwise. They need a lubricant to get seated correctly.

Try UHMWPE for your cone tools; it should survive an occasional drop without scarring.



Mike Halloran
Pembroke Pines, FL, USA

 

[FACS]

You can roll an ORing to get it on, but when it is in the gland, it can not be rolled; this will affect the diameter, and depending on the application, will affect the seal.

Light oil is not recommended for lubrication. Use petroleum jelly or silicon ORing lubricant.

If you can make your cones out of sleet they will last longer and you can get a good finish on them.

Charlie

http://www.facsco.com

 

[JDana]

Every time I make try to make something out of sleet it melts before I'm done.

 

[FACS]

Yeah, I might have meant steel... but the way today is going....

Charlie

http://www.facsco.com

 

[FACS]

Also, I might add, that too smooth a surface finish makes the ORing "squeege", that's why it sticks sliding across the teflon. You can have too fine a finish.

Charlie

http://www.facsco.com

 

[VNestico]

I have several feeder bowls for smaller o-rings (5-6mm) which are fed into a mandrel that stretches them over the OD of the receiving component. It is lightly lubricated with a silicon oil.

 

[amerigrip]

You can use a pneumatic o-ring installer that can be bench mounted or used in an automated assembly machine. The unit will spread the oring and eject into the grove. The company is AGI and the part is AGP-6 OR under grippers. The web site is

http://www.agi-automation.com

 

[dblcrona]

I found the solution to my o-ring installation problem. Our old mandrels were made of aluminum with a 5 degree taper. I had our tool room make up a new mandrel from Teflon with a 10 degree taper. The steeper angle makes it dificult for the o-ring to roll during installation.