O-Rings as vacuum seals?

[tim_mcknight]

Has anyone used O-rings as vacuum seals beneath small wooden parts? I am currently using AllStar Adhesive seal tape and it works well to seal against vacuum leaks and to hold the part in position. However, there is some variation in the finished machined surface, over a 20" length, that I believe may be caused by uneveness in the compressabilty consistence of the seal tape. I was wondering if an o-ring may reduce machined surface variation and be more consistent. I am not sure if it would work well to seal and hold a vacuum on small wooden parts though. Any O-ring users out there?

[carlcnc]

Tim
I have used o-rings in the past, you can buy it by the roll in various dia and durometer from McMaster,
how small a prt?
really small parts having less than 2" of surface area
are nearly impossible, try using sign application tape on back of material,then glue the whole thing to a temporary waste board with 77 spray glue,
works well
Carl

[stevem]

The thick sealing tape (>.125) is intended to be embedded in a slot cut into the table surface. When vacuum is applied, the tape is compressed until the machining stock is sucked down to contact the table surface and remains flat.

AllStar sells thin tapes made from harder rubber. These tapes are intended to be used on the table surface and will compress much less than the thicker tapes. The thin tapes also increase traction as opposed to only the friction imparted by the table surface.

You might want to try one of the thin tapes. They are much easier to use than O rings.

[Gary Campbell]

Tim...
AllStar also sells different grades of O rings or Donuts made for exactly what you are trying to do. Contact them, they have done the research and have the right product for the job.
Gary

[gpari]

I try to embed whatever material is being used into the fixture to the point that it compresses and bottoms out the fixture to the table. Then you don't have to worry about the fixture changing heights across the table.

I have used fancy masking tape, cheap weather-stripping from the orange box store, foam rope from mcmaster-carr and whatever else I have lying around. It all works fine as long as it compresses enough the bottom out.

Gabe