Vacuum Pump Question for Chuck

Bill Noble has put together some very good information on vacuum chucks and the requirements for pumps. The information can be found at:

He usually has some good deals on used pumps as well.

Marv you can have anything you like in principle.

The cfm of the Pump, lets say 2.5cfm, will dictate how quick you evacuate the System, i.e if the internal volume of the Chuck + the piping + anything else between the Workpiece on the Chuck and the Pump was 2.5 cubic feet then it would take a minute in reality any system is probably no more than say a

20th, or even smaller, of that so at the worst 3 secs would be needed to pull a good Vacuum.

I have built my own System and details are on my Web Site in the Hints n Tips Section.

"Richard Stapley" wrote: The cfm of the Pump, lets say 2.5cfm, will dictate how quick you evacuate

^^^^^^^^^^^^^^^^^^^^^^^ This is correct, but I think there is another, important issue relating to pump volume. Any pump capable of pulling an acceptable vacuum (say, in the range of 10" to 26") will work with a vacuum chuck, *provided* there is not enough leakage to defeat the pump. If you try to get by with a low volume pump, you will work MUCH HARDER getting everything sealed. Very often, getting the vacuum started is part of the process of making the seal. Initially you are working against small gasket leaks due to seams, flaws or non-flatness. As soon as the seal "takes hold," the leakage decreases, and the vacuum jumps up. A small pump may not get you through this startup process, so you have to be much more careful to get everything right. Furthermore, some wood has its own leaks, and a little extra capacity in the pump is essential.

I use a Gast vane pump with a 3/4 HP motor, and never have a problem.