You don't see brass much anymore because the Zn component has a marginally high vapor pressure. But, for 10-5 Torr and above, provided that it is not going to get excessively hot (250 C at 10-5 would not be a good idea), it works fine.
Do be careful of some brass castings as they can be porous. I routinely use brass vacuum valves (bellows style) and they do fine in most applications.
Steve
Created on Thursday, March 01, 2001 7:26 PM EDT by Steve Hansen