Slightly OT: Rectangular O-rings

Probably already checked but...

Any chance this Expresso parts place has something close enough?

The dimensions may well be metric.

Would a Parker X-Ring Seal work?

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Joe Gwinn

Is there a standard catalog of rectangular cross-section O-rings? It's a hot-water application, in fact the group gasket for an old espresso machine.

The dimensions need to be about 2 1/4" OD, 1 7/8" ID but a little over 1/4" thick, say 5/16". The thickness is the sticking point.

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Disk brake calipers have similar seals, though selecting them by size instead of vehicle might be difficult.

When I couldn't find the exact OD, ID and length for a hydraulic cylinder seal I machined a spacer to adapt the closest match.

Is there a standard catalog of rectangular cross-section O-rings?

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How about two cup seals?

Place the flats against the groove walls, not each other back-to-back, so the loaded one doesn't crush the other.

No, I didn't know about that one. Good find, and bookmarked.

Nothing by manufacturer (Olympia) and nothing obvious by nominal size (49 mm). That doesn't mean they don't have what I need, but it'll take some digging.

It's a good web site, thanks for making me aware of it!

bob prohaska

If so, they're very oddly chosen. 58.2 mm OD, 47.5 mm ID, thickness is a bit vague but 7-8 mm seems to be the range.

Not in a straightforward way, if I'm understanding the sizing pattern correctly. The trouble is the thickness needed, too big for the OD.

For the moment I've stuffed a 2-034 o-ring under the (too thin) Teflon flat gasket I have now. That shimmed it up enough to let me make coffee.

Thus fortified, I'll explore further!

Thanks for writing,

bob prohaska

I didn't think of brake parts. The seals won't be food-grade, but anything that can withstand hot brake fluid is likely to be pretty inert 8-)

It turns out O'Reilly's Auto lists replacement pistons by OD, the sizes step from 57.7 to 59.2 mm. If the photo is any guide, the seals are much too skinny, but it might be worth a visit.

That's sort of where I am now. I use the Teflon for structure and add an o-ring groove on the rear face in order to obtain the overall thickness.

Thanks for writing!

bob prohaska

Why not just machine the whole seal from solid Teflon, starting with solid Teflon? It may be the cheapest way, unless one can find the expresso maker.

Joe Gwinn

That's roughly how I got to where I am now. I could do it again, but was just hoping for something easier and less expensive. Looks like it'll be easier _or_ less expensive. Teflon is too soft to chuck, so at least one and maybe two mandrels will be required. Memory has gone rather hazy, the gasket I carelessly damaged lasted more than twenty years. Only then did I discover that the "spare" and the stock I saved were too thin.

What really surprised me was the cost and limited selection of Teflon stock. No more scrap dealers, I guess.

Thanks for writing!

bob prohaska