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O-Ring Groove Design

O-Ring Groove Design

O-Ring Groove Design

I've made a few parts with o-ring grooves, but I had always just 'winged' the dimensions & mostly have been getting away with that

But now that I'm designing an assembly that requires a bit better precision, I've realized that I've never really understood the specifications listed for specific o-ring sizes

So this is a really entry-level question I have, to make sure I'm understanding this correctly

The o-ring I'm working with at the moment is a AS568-113, an X-ring in a shore 90, intended to seal gas pressures up to 2000psi. I've seen one supplier state a nominal OD of 0.755, ID of .549

The application is a female gland, so a fixed seal with a shaft sliding past it

Listed squeeze is: 0.010~0.019", so I might try 0.014" just to get a trial fit

So, I should machine the shaft to be 0.549" + 0.014" = 0.563" & the OD of the groove: 0.755" - 0.014" = 0.741"

Assuming I have good numbers for the o-ring nominal OD & ID

Yesterday, I cut some scrap and sized it so the o-ring seemed to slide onto it ok. But when I sat down to measure that, I see I managed to get something really over-sized! 0.618"

I'm also not so sure how I should measure the groove OD, as my calipers wont work and none of my bore gauges. I'm planning on using a bore gauge to set a clearance OD of 0.56~0.565"

Change out to a tool for cutting the groove, go a couple passes, then squish some modelling clay into the groove and try measuring that on my caliper, as a way to check my progress on the lathe

The groove width is about 0.12", so not a lot to get a measuring tool into

I wish I had a reference for groove dimensions for each size. It seems this is something I just have to write-up myself for the applications I working with

RE: O-Ring Groove Design

Nice handbook! Has quite a bit more info than what I've found so far. That & I didn't know Parker has 200 plus compounds. The outfit I've been buying from only has around 30 actually in stock. I started reading the dynamic design section & had to stop because this project will never get finished if I start re-designing now!

I totally regret not buying that caliper, back when I was shopping for a replacement & saw that type. Model 573-746-20. I'm just concerned about how tall the pins are. But they look like they should work for this one job. Bottom line, I need something now. I might play around with adding wax to modelling clay & do a test run in aluminum

Putting the o-ring in to measure it's ID is a nifty idea, but I'd like to keep the lathe tool in place so there's no chance of having it's zero shift. The lathe is old and getting it back to where it stopped doesn't always 'go well'

RE: O-Ring Groove Design

The X-ring is stiff enough, I decided to try measuring it without a cone gauge. Though what I wish Santa would bring me is an optical measuring system for size, roundness & surface roughness. Other applications for that

The catalog numbers are not exactly the same as what I'm seeing on my desk

CS listed - .103, measured - .100

OD listed - .755, measured - .755

ID listed - .549, measured - .555

No dissenting opinion on how I calculated the target shaft OD & groove OD, so I think I'm understanding the specs ok

Those calipers are out of budget for the time being. Just about $1000, and even if, would take some time to get here. So I'm even more inclined to just gauge the groove with clay

RE: O-Ring Groove Design

The Mueller gauges look decent, but still out of my budget for the time being

The most important thing is that I have the right idea on how to establish the correct dimensions, before I start cutting steel. I'll improve how I measure as I do this more often. Hopefully I'll be doing this more often!

RE: O-Ring Groove Design

You might want to investigate dental putty.Not the alginate stuff. The two part silicone type. It's non-shrinking and sets quite firmly.
Just make a small ball of it and press into groove (part circumference). Wait 10min, pop out and measure.

Politicians like to panic, they need activity. It is their substitute for achievement.

RE: O-Ring Groove Design

Dental putty sounds useful, I'll look into that

I'm still going to try clay, as I'd like to only wait 3 seconds in between cutting passes

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