vacuum pump question

[Larry Pickering]

Every thing I have read on vacuum systems, they call for an oil-less pump, why?

Most of the Gast pumps I'm finding have oilers on them. and I'm just wondering what difference it makes.

Larry Pickering

[Richard Allen]

The oilless pumps are noisier and they have a shorter life span. The oiled pumps are more selectable to contamination from sanding dust. A filter eliminate the dust problem and all systems should have a filter. You can often use a vacuum pump as a low volume compressor for perhaps an air brush or for a small blast of air to move shaving around. An oiled pump will almost certainly contaminate an air brush or whatever you blow air on. You can attach an oil separator to the output side but they tend not to be very effective at the low volume of these small pumps. Oiled pumps also give you something else to worry about, is there enough oil, what type of oil should I use, should I change the oil.

[Scott Crumpton]

There are pros and cons to each. If you can't stand the odor of a little air tool oil, then don't get an oiled pump. Oiled pumps spew oil vapor, oilless ones spew carbon dust as the vanes wear. Appropriate filters on the output as well as the input are a necessity.

I have a Gast oiled lab pump, the one with the two gauges and filter jars. Got it used on ebay. It only pulled about 15" of vacuum when it arrived. I suspected that it was simply "dry" or contaminated and that one or more of the vanes were stuck. So, I dripped oil directly into the oil port for about an hour to lube it up and clean it out. It's been pulling its rated 24-25" ever since. I have the oil wick arranged so that it gets a lot of oil. I do have to fill the oil bottle and empty the oil trap/filter frequently. But it will probably out live me. If it had been an oilless pump I would have had to buy a rebuild kit and replace the vanes.

[Larry Pickering]

Thanks for the info, now I can concentrate on the important thing, price

[Ralph Lindberg]

Larry
If oil is in for you, look at the pumps from Harbor Freight. Several of us use the A/C evacuation pump that they sell. But all the smart one use a filter between the chuck and the pump

[David Lancaster]

Larry

Either pump will work fine but try to get a pump that moves 5cfm's of air and install a check valve for safety.

[Bruce Markwardt]

Larry
If oil is in for you, look at the pumps from Harbor Freight. Several of us use the A/C evacuation pump that they sell. But all the smart one use a filter between the chuck and the pump

Checked their website and they had a couple of A/C evacuation pumps. Which pump do you use?

[James Combs]

Not trying to answer for Ralph but I would go for the 3cfm unit. As David Lancaster said 5cfm would be better but 3cfm will work fine if you have a good tight system(minimal leakage). The basic difference in low cfm vs high cfm is length of time to evacuate to the amount(inches of hg) of vacuum you need, whether it is a refrigeration system or a vacuum chuck.

[Ralph Lindberg]

I actually use the 2.5 CFM (on sale plus a 20% off coupon). If I have good wood, I can get 27 inches of vacuum.