Vacuum Chucking Question

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Forum topic by JamesVavra posted 935 days ago 747 views 0 times favorited 3 replies Add to Favorites Watch
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286 posts in 1948 days

935 days ago

I just setup my new vacuum chuck system. I’m using a refrigerant evacuation pump as seen in the photo below:

When the vacuum is at less than full pressure, there is a fine mist that comes out of the output side. The mist goes away if the vacuum is at full. I’m wondering what the mist is – is it just water vapor, or pump oil? It doesn’t feel oily or damp and has no odor.

The first chuck I threw together worked like a dream. I turned a platter, and then reversed it and took the foot completely off. Looks like it will also be really handy for off center turning.


3 replies so far

View hairy's profile


2007 posts in 2164 days

#1 posted 934 days ago

Most likely water vapor. Lowering pressure lowers the boiling point, water will boil at less than room temperature in a vacuum.

Is that a 2 stage pump?

-- the last of Barret's Privateers...

View JamesVavra's profile


286 posts in 1948 days

#2 posted 933 days ago

It’s a single stage, 1.5 CFM pump. I was thinking the same thing with water vapor, but now I’m leaning towards pump oil – after running for an extended period, it was pretty oily around the base. It seems that overfilling the oil reservoir will cause this.

Actually, it’s probably a combinatino of the two. fortunately, the lines are long enough to run it outside for a while, to burn through the extra oil. It’s right at the fill level line, but apparently too much.


View Grandpa's profile


3095 posts in 1307 days

#3 posted 933 days ago

It could be both. Refrigerant compressors and pumps are made very much the same. They both pump a little liquid as well as the refrigerant. This should be mostly water. That is the way water is removed from a refrigeration system. That is the reason for pumping the vacuum on the system…well, one of the reasons. Watch the oil reservoir and don’t burn anything up but see what happens. Some good ideas here.

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