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O-ring modification

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  • O-ring modification

    A person has to get lucky sometimes??

    I have been scrapping some heat pumps lately, but that is another long story.

    This entails removing the refrigerant from the system before breaking the sealed refrigerant circuit. One of the tools involved in this process is a tool that removes the schrader valve core from the access port, while the port is under pressure, so the pump doesn't have to suck the Freon past this restriction.

    This tool uses a couple small (tiny) o-rings to grab the flange on the end of the stem. Naturally these o-rings get torn up when the core is removed from the tool, so I dis-assembled the tool to see about replacement.

    On closer inspection it seems that these are a custom size O-ring, a -001 being too small and a -002 ring seemingly having too a large cross section. One problem with the design is that the flange on the stem of the core must squeeze through the hole in the O-ring while being resisted only by the small spring that holds the core closed. This is not a very robust spring and the flange would not go through the O-ring when the O-ring was installed in the tool. I could get it to go through when I pushed the O-ring against my finger, so I thought that if I would remove some material from the OD of the O-ring it would allow it to stretch enough to work when it was in the tool.

    But how to remove material from an OD that is .140" dia. AND made of rubber?

    See the results of holding the O-ring on a pin punch and using the disc sander to remove .010"-.020" from the OD of the O-ring. It rotated on the punch just enough to make a fairly consistent flat and the tool now grasps the core with something approaching reliability.


  • #2
    I've modified several O-rings using the TP grinder. Rubber dust gets everywhere, but it works very well. I turned a large O-ring into a V belt for the Unimat once.

    For small rings, and where you might not want to set up the lathe and grinder, you can chuck a length of rod in a cordless drill. With the ring set on the rod, you can guide the very end of the rod in your fingers while bringing it up the sander. If the rod is long enough, any off-centering effects from the drill can be eliminated. You can get a very good result this way. You can grind it on an ordinary grinder as well, although myself I've become quite partial to the belt or drum sander.
    I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-


    • #3
      Try freezing it as well with an inverted air duster or pipe freeze spray too, you get a better finish an rounder ring as it can't distort so much.