On 13 May 2005 10:45:09 -0700, jim rozen
wrote:

In article , Chuck Sherwood says...

Will a two stage pump work faster or slower ?

Two stage pumps will go down to a lower pressure.

Typcially five or ten microns (1 micron = 1 millitor)

A single stage pump might do 40 or 50 microns ultimate
pressure.

Related question: what does "gas ballast" mean in the context of
vacuum pumps, and what is it for?