Molding custom gaskets or O-rings?

What is special about them? Can't you design around off the shelf ones?

-- Randy Replogle

My wife says I'm doing my Christian duty... annoying the hell out of her. Randall Replogle 2006

Randy,

No, I can't design around commonly available ones. I've tried, but the profile I *need* to have makes using stock ones problematic. There's 8 outside curving bends, and 4 inside curving bends that are necessary to move around obstructions and stay within the sealing surface. Plus, I've tried altering the path of the groove I insert them into but can't get it to fit a stock size perfectly, either. So... any leads on DIY rubber gasket/o-ring molding? :)

Best,

Weyland

If you can use a standard round or square cross section and just need a non-standard length, but o-ring cord stock and splice it with Loctite

404. See McMaster p.3217. Cord stock is on p.3282. Unfortunately, 404 is expensive and has a relatively short shelf life, but it makes a surprisingly strong joint that works fine for static seals.

Ned Simmons

You can make a mold out of a nice machining, low stick material like machinable wax or delrin. You can then use RTV or silicon to make the gasket. I bore a hole through one side of the mold and use a plunger to push the material through the "sprue", down a runner which goes past the cavity a little ways and gate into the cavity. Other people inject right into the parting line and use a syringe. A little slop in your parting line will help vent air. Some areas may need "risers" to prevent air pockets.

--You need to get into razor dies and "clickers"; watch your fingers! :-)

Super glue also works for this. Though if exposed to water it may fail. It sure doesn't when in an oily area. ERS

if you know the length of your groove in linear dimensions based on the inner dimension i can find you what you need , it may be a metric cross section but there is something you can use .

dont forget when inserting an oring into a groove that will mate with another flat plate it is usual for the oring to actually be about 5 % to long and be inserted and held in place with a little silicone o-ring jelly for assembly

Hi Ned,

This is exactly what I have been doing, but it's getting old, fast, and ideally I'd like to be able to simply lay a gasket or o-ring of matching profile into the groove I have machined for them.

Best,

Weyland

I thought about steel rule dies, but was thinking that there'd be a lot of waste resulting from it, economically negating any time savings I might actually gain.

This is approximately a 4" x 2.5" rectangular shape, with both inside and outside radius bends at all four corners for going around the four screws that are located there.

And the seal is only .063" and I can't go any larger.

Best,

Weyland

*THIS* is *exactly* what I have been contemplating. I've been thinking to make two halves, pinned for locating, and with some way of forcing (by way of pressure) a medium into it to make the gasket/o-ring.

I'm just not knowledgeable about what material to use and what's available that will fill my need while being able to be used for making these things.

... things like how do you cure them efficiently?

Are there sites that I can research this stuff on?

Thanks.

Best,

Weyland

There's something I might be able to use... What's this "silicone o-ring jelly"? I've been super-glueing them in place, which is part of what's a hassle about it.

Best,

Weyland

you can use grease or petroleum jelly , the oring should be a litlle larger than the groov to allow for compression

there are form in place gaskets available , permatex and loctite make them , just like running a bead of caulk , wont hold a ot of pressure though

do you know your linear dimension [ how long the seal would be streched out straight?

Shouldn't the *groove* be a little larger than the O-ring?

Mike

Ahh, okay. That won't work for me in this instance. I need to be able to lay the gasket/o-ring in the part. The part gets shipped out for installation by the end user.

Pressure's not the enemy here. Moisture intrusion is.

Yes. 13.39128" I could *theoretically* tweak this a bit more to get to 13.375, but it all *SEEMS* (to my admitted ignorance) to come down to a "046" o-ring. ... which in actual execution just doesn't seem to fit quite right...

Part of the problem, I believe, is the contours (the inside and outside bends) at the corners making it want to not "stay" put. I finally got an example of it for you guys, here -

I'd very much like to just have these molded for me, but like most others here, simply cannot afford it, which is why I thought to venture into the DIY arena of molding for these.

Thanks,

Weyland

I've never tried this, but a grease gun produces a lot of pressure, and can be bought pretty cheap.

How about water jet? You could find the material you want in a sheet and have them water cut to the shape you want.

I agree that waterjet would probably be a good way to go. You can do just about any shape from just about any material. (Or even cut different materials glued together, etc.)

If you need to find a job shop to do work for you, visit:

or

- Carl

Dave Ly> > I'd very much like to just have these molded for me,

Just supply a small tube of form-a-gasket type stuff with the part and be done with it. Ford uses some sort of stuff like that on their later differential covers, no gaskets at all, just a groove for the goo. Seems to work, I've had mine off a couple of times and other than the hassle of peeling the old stuff out of the groove, it works just fine. You just need to find a sealant that works in the conditions you've got. Silicone won't work if there's gasoline around, for instance.

Stan

Yep, maybe he meant a little "higher". About 30%.

-- Randy Replogle

I've found that relationships are like a bell curve. You love a few, hate a few, but most you're just indifferent to.

-- Randall Replogle 2006