Knob seal

Install a stud that is sealed against the surface the knob attaches to, so that no penetration exists.

Install an o-ring in the base of the knob, complete with a groove in the base of the knob to get correct compression of the o-ring when the knob contacts the surface.

Use epoxy and a simple stick-on "block" that will allow only sufficient mechanical force to open the cover, and not break the adhesive bond.

Injection mold the "knobbed cover" with the knob built right in.

"No user serviceable parts inside."

Just some ideas.

David A. Smith

shaft seals are metal lips cast on steel caps, with a spring encircling the lip's shaft contact area. The cap is cemented in place to a fixed recess, and the rubber lip bears on the rotating shaft. They can be arranged in series, and with the lips' sealing direction opposed. But a hermetic case pressurized just barely above the highest ambient pressure will be a big help to any water seal of this kind.

Brian Whatcott Altus OK

Oh hum: RUBBER lips cast on steel cups...

dmd, You don't say what type of device that your knob is attached to. I assume that its for some sort of rotary switch, potentiometer, or variable capacitor.

Instead of coming up with your own seals, It would be a lot easier and more reliable to simply replace that component with an component that is manufactured with a splash-proof shaft seal and panel seal.

For example, ITT-Cannon's model C&K M Series rotary switches can be purchased with splash-proof seals. See page 5 of:

Almost any manufacturer of Mil-Spec rotary switches, potentiometers, or variable capacitors produce a few splash resistant versions of their products.

Happy hunting

Or stick your control in one of these...