O-ring placeholders... Figuring out


Hello guys,

Any o’ring specialist here ?

  • is it better to choose an o’ring slightly smaller than the space where it would sit into, so that it spreads a bit when being installed ? Or should it be the exact same diameter as the channel width ?

  • what width for the channel it sits into compare to the thickness of the o’ring, knowing that it will squeeze even more when you press-fit the tube ?

  • how deep should the channel be ? 1/3 of the o’ring thickness ? 1/2 ?

  • should the channel shape profile be a square or rectangle ?

  • what o’ring shape would do you prefer ? Round, cut square, quad ?

Thank you


There is quite some science behind Orings. The Parker Oring handbook helped me a lot: https://www.parker.com/literature/ORD%205700%20Parker_O-Ring_Handbook.pdf


O-rings are a thing that engineers don’t know by heart. You typically let o-ring manufacturers advise you on that. They all have PDF guidebooks or even online calculators where you input your parameters.


maybe this helps you



Found this excellent guide explaining with basic words what to look for :

I did not realize that there should be some angle (alpha on the below graph) along the groove depth. It does make sense.


Its true you should have some angle and radii in the corners and probably the most important factor is the extrusion gap. However, keep in mind that o-rings are capable of sealing pressures up to 5,000psi. So in this application its ok to cut corners and simplify things. The parker o-ring handbook is a great resource.