Vacuum pump Help

[Jason Courneyea]

Hello sorry have been away for awhile but i have a question regarding the ability of this pump to be used in a vacuum chuck system. I am getting allot of conflicting numbers in regards to the actual inches of Hg that this will pull. I believe it is 5Pa but aside from that the conversion is confusing. The reason I chose this one is its local and considerably cheaper than a gast. any help or suggestion would be greatly appreciated.

252329
Thanks, Jason

[John Aspinall]

That looks like a laboratory vacuum pump. The pressure rating says (I think) 3 x 10-1 Pa., or 0.3 Pa (Pascals). That's a really good vacuum.
Even if it's been downgraded to 5 Pa, that's still very good.

(For comparison, atmospheric pressure is about 105 Pa or 100,000 Pa.
If you want to express pressure in inches of mercury, atmospheric pressure is about 30 in Hg.
Or you can just type "5 Pa to inches of mercury" into Google.)

Leaving science class, and back to the woodshop, the other rating that matters is how fast it moves the volume. 3 CFM (cubic feet / minute) is not such a great rating, but workable. (Or so says my summary of the various vacuum chuck threads around here, that I've been following.)

[Jason Courneyea]

Thanks John. from the other pics I believe it is an A/c service/recharge pump. they also have one available with 5 CFM and 5Pa. in your opinion would be sufficient.
Thanks again.
Jason

[Steve Schlumpf]

Jason - a lot of folks use small vacuum pumps (Harbor Freight) that pull less CFM than 3 and they work just fine. All it means is that you might have to wait for an extra 1/2 second. I would think the pump you are showing would work just fine! Give it a shot and let us know what you think once you get your system up and running! Oh, and some photos of your system would be much appreciated!

[Mike Cruz]

I'm not an expert on how much CFM you need. The only challenge I would see is if you do have a small leak (from the wood, say), your unit may or may not be able to keep up with that leak. A great example of a contributer to leaks are the holes in ambrosia maple.

Anyway, other than that, the only down side I see to that pump is that it is not an oil-less pump. Which mean, from what I understand, that the air in your shop can get...cloudy if/when your pump runs for a long time. My pump is oil-less. So, I haven't experienced the cloudiness...just what I've heard about them.

[Jason Courneyea]

Ok so the pump i am looking at now is 5CFM and 5Pa single stage rotary vain pump. when i did the conversion this is what i come up with,
"5 pascals = 0.00147666864 inches of mercury"
now this looks wrong to me initially, unless this is calculated opposite for vacuum.
anyone know?
Thanks Steve and Mike I will start the build as soon as I get the pump and post some pictures. The plumbing portion of the system seems pretty straight forward especially with all the threads i have been reading.

[Paul Gilbert]

That calculation is correct. This is overkill for pressure, but the 5 cfm is what you want for leaky gaskets, wood, etc. Be sure to install a bleed valve on the suction side of the pump, because you can suck the bottom out of a platter with this.