Vacuum Pumps

[bonsaipeter]

I have heard that some folks use a compressor unit from an old air conditioner or refrigerator as the vacuum pump for a vacuum chucking system. Has anyone actually done this and how well does it work? What does one have to watch out for?

Thanks, Peter Toch

 

[john lucas]

I used a compressor from an old car. You have to weld up the clutch on the drive pulley but it worked very well until I got a used Gast pump to replace it.

 

[Mark Mandell]

That is what I use. See pic.

Couple of points to remember:

1. Size matters. Frig compressors are too small; don't move enough air. Look for something out of a 50 pint dehumidifier or 1 ton+ a/c unit which will give you around 2.5 CFM. That's why I use 2 of them in parallel. You can get these things for free for a nice applicance shop to whom they're just junk after the freon is removed. I have 2 spares sitting on the shelf.

2. You will need a cooling fan to blow on the compressor shell during use. These units have an internal thermal overload circuit which will stop the thing, so that your bowl will launch with no warning, when the housing gets too hot. With the fan, the things will sit there and run all day. Hint: The circulation fans from the old appliance (also free) work great for this.

3. You must have an in-line dust/water filter between your lathe and the compressor. These things are oil-lubbed and dust and water in there will gum things up in short order.

4. If the appliance has an external capacitor included in the circuit, make sure that you put it into your circuit or else your compressor won't start/run properly.

5. Running open in this application, the compressors will put out a fine mist of oil. This in NOT good to breath. Make a condensing coil or use a filter on the exhaust side to prevent this problem. I get, maybe, a tablespoon of oil in the condenser after a month of use. I also give the pumps a small drink of synthetic compressor oil a couple of times a year, and so far, so good.

PS: The intake tubing on most of these compressors is 5/16" copper. The only place I've found that has fittings to go from that to other pipe sizes is an auto parts store.