Need Help!- Gasket material for Vacuum Workholding

[tminnig]

I am getting geared up to implement some vacuum workholding at the shop where I work. I have been told that there are several gasket materials and O-ring materials that are available, but that many will not withstand the machining environment and will break down in coolant. We are using Blaser Vasco 1045 cutting fluid, if that helps.

I was hoping someone here had some experience they would be willing to share on this matter.

-Are there any materials that I should stay away from?
-Are there any you've had great luck with?
-Also, what is the best way to join the ends so I don't have a leak where they meet?

Thanks in advance for any and all help.

Travis

[Cartierusm]

The people at allstar gasket will be able to direct you. They make products especially for vacuum holding. They can tell you exactly what you need and are very cheap. Just make sure when your making a mold or board that you do have grooves in it that are about 3/4 of the gasket thickness deep. You want this so the work piece touches the gasket but crushes enough to bottom out on the vacuum board thereby allowing repeated setup and uniform height.

[Geof]

Regular neoprene O-ring material should be fine for most coolants and you can get it in cord various sizes.

You can often get away without joining the ends; just cut the cord slightly longer than the groove length and butt them together. If you want to glue them use a flexible crazy glue; the O-ring cord supplier probably has the type needed.

As Cartierusm mentioned make the grooves slightly shallow so the O-ring cord is compressed. In our experience 3/4 of the diameter may not be quite deep enough depending on the area under vacuum and the thickness of the part because it does take quite a bit of force to compress the cord. You may need to experiment a bit. Get a soft grade of Neoprene, 70 Durometer I think may be the softest available, as this allows for more compression. Also make the groove 20 to 30% wider than the diameter of the cord so it has room to expand sideways when it is compressed; use the measured diameter not the nominal as O-ring cord is oversize slightly.

[extanker59]

I used to design valves that used o-rings. I used the Parker O-Ring book for the dimensions. It really helped. A bit hard to get started but once I got what they were doing it was easier. We got the book (catalog) free just by asking for it. I wonder if that info is on-line now?
I'm sure that Geof's way would work too.

[extanker59]

Here's the link to their pdf:

http://www.parker.com/literature/ORD...g_Handbook.pdf

Ah, brings back memories. They have improved the book since I last used it. Interesting stuff. The company I worked at sucked but the work was interesting.

[skeetman]

Try the link below. We use this and it works great.

http://www.workholding.com/vAccssors.html

[tminnig]

Thanks for the responses so far, everyone. I appreciate your and anyone else's help on the matter.

Thanks,
Travis