SpudFiles

There are several applications for which I need rubber seals on an extremely small scale. For example, I would like to machine a miniature TAC (brocock tandem air cartridge) in around 2mm cal. The smallest O-rings I can get for this are much too large. In this application they work in a similar way to a quick dump valve crossbred with a toolie valve opened by a hammer.

What's the best way to go about making these seals? Drill a hole in rubber sheet, epoxy it on then turn it down on the lathe?

Any ideas?

inonickname wrote:There are several applications for which I need rubber seals on an extremely small scale. For example, I would like to machine a miniature TAC (brocock tandem air cartridge) in around 2mm cal. The smallest O-rings I can get for this are much too large. In this application they work in a similar way to a quick dump valve crossbred with a toolie valve opened by a hammer.

What's the best way to go about making these seals? Drill a hole in rubber sheet, epoxy it on then turn it down on the lathe?

Any ideas?

Alternatives in that scale include the rubber bands used in dental braces. Look for Orthodontic products.

http://www.orthomechanic.com/store/prod ... =12&page=1

1/8"..sounds close, but might not hold up under high pressure. If these work out well I could make a jig and fill them with a fridgy..

I'm thinking punch a hole in my 6mm neoprene sheet, spread thin epoxy over the reduced section of the shaft, force rubber over then trim around. When dry turn round with lathe.

I'm also looking for a way to fill the bloody things that can be adapted to a common thread. (eg. schrader)

inonickname wrote:1/8"..sounds close, but might not hold up under high pressure. If these work out well I could make a jig and fill them with a fridgy..

I'm thinking punch a hole in my 6mm neoprene sheet, spread thin epoxy over the reduced section of the shaft, force rubber over then trim around. When dry turn round with lathe.

I'm also looking for a way to fill the bloody things that can be adapted to a common thread. (eg. schrader)

Ask your dentist for free samples. Saves money on both the purchase and shipping. I use those little buggers on the stems of the keys on my keyboard for stealth silent typing.

If tiny orings you want go open up a disposable lighter, take out the "outlet valve" it has 2 very small orings i calculate 1.5 mm or 2mm , not sure. Just look around different valves, most tiny ones use 2 orings for sealing. Carerful when taking out the valve in the lighter, wear gloves or take it out fast..

Have you considered making your own o-rings? Most hardware stores sell o-ring material that can be cut and trimmed to the desired length.

Another option (and probably cheaper) is to try rolling a strip of teflon tape until it is the right diameter. I don't know much about the smaller applications but this technique (which was actually not mentioned) was what I did in The Sprinkler Valve to seal the valve for the piston and diaphragm upgrade.

Hubb wrote: Another option (and probably cheaper) is to try rolling a strip of teflon tape until it is the right diameter.

That idea will work for a static seal, but I can't see it holding up under dynamic sealing (if he needs his sealing faces to move).

Hubb wrote:Have you considered making your own o-rings? Most hardware stores sell o-ring material that can be cut and trimmed to the desired length.

Another option (and probably cheaper) is to try rolling a strip of teflon tape until it is the right diameter. I don't know much about the smaller applications but this technique (which was actually not mentioned) was what I did in The Sprinkler Valve to seal the valve for the piston and diaphragm upgrade.

For my 2 inch QDV I did for a long time until I found a source of the right size rings. I couldn't find a hot vulcanizing kit. Rubber cement has no strength for pulling. It peels right apart even with several days of cure time. Instant glue (CAV) is better but wasn't up to the task of high pressure floating rings. Teflon blows out and only works where firmly clamped in threads. It's useless in moving joints.

I stand corrected. I kinda dismissed the idea of doing this with a moving part. In the above image, I didn't even secure the teflon. I just wrapped it and tucked it in the groove.

Thanks for the correction fellas.

o-rings are available all the way down to 1mm id and .25mm cross section... check auto parts stores...