Machining O-ring grooves?

[customcutter]

I did an advanced search and there's not much information.  The only thing I did find was a reference to Parker's O-ring Handbook.

I downloaded it and tried reading through it and came up with on a "faceplate" application the "squish" is usually in the 20-30% range.  However, when I looked at the other applications the formulas just didn't add up for me.  I tried copying, etc but was unable to grab any images.  On page 4-5 there is a diagram of a male and a female application and talks about groove depth, but like I said the formula just isn't clicking.

Is there a "rule of thumb" for squish or compression to calculate the depth of the o-ring groove?

[customcutter]

I did a YT search and low and behold I found a short video that explains a lot about o-rings, design, and selection.  The last couple of minutes had all the information I was looking for. 

Apparently stretch and fill are important parameters as well.  I especially liked the part where they talked about backup seals.  I've never seen them used before.

[OTmachine]

If you use the o-ring chart for AS-568 shown here:
https://www.globaloring.com/as568-size-chart/
It will give you basic ratio dimensions.  .070 o-ring cross section for a 1/16” o-ring groove depth.  .103 for 3/32” and so on.  The width usually is not critical as the pressure is usually only in one direction.  And yes,  back-up rings are a good thing.  Helps to keep o-ring from getting extruded past the groove and sheared.

[customcutter]

If you use the o-ring chart for AS-568 shown here:
https://www.globaloring.com/as568-size-chart/
It will give you basic ratio dimensions.  .070 o-ring cross section for a 1/16” o-ring groove depth.  .103 for 3/32” and so on.  The width usually is not critical as the pressure is usually only in one direction.  And yes,  back-up rings are a good thing.  Helps to keep o-ring from getting extruded past the groove and sheared.

I haven't measured many o-rings and haven't cut a groove for one yet.  If I'm reading the chart correctly now the o-rings are already "over sized" for the correct squish based on the fractional measurement.  Thanks for the explanation.

[nced]

I did an advanced search and there's not much information.  The only thing I did find was a reference to Parker's O-ring Handbook.

I downloaded it and tried reading through it and came up with on a "faceplate" application the "squish" is usually in the 20-30% range.  However, when I looked at the other applications the formulas just didn't add up for me.  I tried copying, etc but was unable to grab any images.  On page 4-5 there is a diagram of a male and a female application and talks about groove depth, but like I said the formula just isn't clicking.

Is there a "rule of thumb" for squish or compression to calculate the depth of the o-ring groove?

"Is there a "rule of thumb" for squish
Yep, a lot depends on the oring material, the durometer, the pressure contained, static or dynamic, etc...........


Years ago I started replacing the "thin parachute edge" factory HW95 piston seals with a home turned oring sealed piston cap. I used these charts to get an initial idea of dynamic oring groove dimensions for size 019  and 020 (.70 nominal) orings. The 019 size was used for receivers with 25mm receiver bores and the 020 size for 26mm receiver bores. The material was military spec 75 durometer Viton material...................


I used "lobed Quad seals" for a while and they worked but I reverted back to "round cross section rings" since...........


Hope this helps some!


 

[customcutter]

Thanks Ed!  Excellent charts that I can make sense of.  The charts/formulas in Parkers Handbook were just making my head hurt.   I'll be bookmarking this thread in "my favorites" for reference.

[OTmachine]

If you use the o-ring chart for AS-568 shown here:
https://www.globaloring.com/as568-size-chart/
It will give you basic ratio dimensions.  .070 o-ring cross section for a 1/16” o-ring groove depth.  .103 for 3/32” and so on.  The width usually is not critical as the pressure is usually only in one direction.  And yes,  back-up rings are a good thing.  Helps to keep o-ring from getting extruded past the groove and sheared.

I haven't measured many o-rings and haven't cut a groove for one yet.  If I'm reading the chart correctly now the o-rings are already "over sized" for the correct squish based on the fractional measurement.  Thanks for the explanation.

Yes, American size o-rings are already over sized for nominal sizes, (1/16, 3/32, 1/8, etc.)

[customcutter]

If you use the o-ring chart for AS-568 shown here:
https://www.globaloring.com/as568-size-chart/
It will give you basic ratio dimensions.  .070 o-ring cross section for a 1/16” o-ring groove depth.  .103 for 3/32” and so on.  The width usually is not critical as the pressure is usually only in one direction.  And yes,  back-up rings are a good thing.  Helps to keep o-ring from getting extruded past the groove and sheared.

I haven't measured many o-rings and haven't cut a groove for one yet.  If I'm reading the chart correctly now the o-rings are already "over sized" for the correct squish based on the fractional measurement.  Thanks for the explanation.

Yes, American size o-rings are already over sized for nominal sizes, (1/16, 3/32, 1/8, etc.)

Thanks Keith.   That's what had me confused on the Parkers Handbook.  The only o-rings I've ever measured were metric and their thickness is "as stated".  Like I said it was making my head hurt.