View Full Version : Vacuum Pump Issue

John Cimino
04-28-2015, 3:25 PM
I am in the process of evaluating if vacuum presses for CNC woodworking will work for me so I am experimenting at the moment. I purchased an inexpensive vacuum pump from Harbour Freight to "wet my feet". It is a Pittsburgh 2.5 cfm model (item #98076 from the Harbour Freight website). This is an oil bath type pump used for refrigeration service. When I use this pump it is both quiet and produces good suction (29" Hg), however, it ejects a continuous plume of oily smelling mist. This mist quickly fills my small shop space and I am concerned of both the health risks and contamination of my shop environment (as I finish my projects in the same room). Of course I have followed the pump manufacturers directions (used their oil filled to the appropriate level).

I am looking for advise on how to best deal with this? Perhaps someone has solved this problem?

I can think of five possible routes:

1. Pipe the exhaust outside. If a large pipe is used the back pressure would be small.
2. Filter the exhaust. I need an inexpensive filter recommendation that would be effective at removing the oil from the exhaust.
3. Use an alternate oil. I used the oil that came with the machine and filled to the appropriate level but perhaps someone has solved this issue by using an alternate oil?
4. Locate the pump outside and pipe the suction side to the CNC machine. Not my preferred option as I am worried about theft and noise to the neighbours.
5. Try an alternate pump (again looking for recommendations at the same price point of $100).

Any ideas?

Tony Joyce
04-28-2015, 4:18 PM
2. Filter the exhaust. I need an inexpensive filter recommendation that would be effective at removing the oil from the exhaust.
Any ideas?

A crankcase vent filter will work, but it will only reduce the mist not eliminate it.


You can get oil less vacuum pumps, but they generally run more.


Jamie Buxton
04-29-2015, 1:13 AM
google with "vacuum pump oil mist filter"

Steve knight
04-29-2015, 1:44 AM
Just light the mist on fire and use it to heat your shop while running the cnc. the problem is air is going to carry moisture into the oil and it will need changed more often. a pump like this is a much better choice .

Mike Cutler
05-01-2015, 9:38 PM

I've used that style of pump for many, many years and it will always emit some amount of oil vapor. I've run them as along as 7 days straight, 24/7.
There shouldn't be a mist plume though, and if the smell is driving you out of the shop, I'd go to a synthetic vacuum pump oil.

I would either locate it outside the shop, because you are correct in assuming that there will be some amount of oil in the air, or enclose it in a breathing box.