I'm looking for a vacuum pump for vacuum chucking and have found lots of used pumps for sale, but very little info on the specs for specific pumps. I've read the general info here on pumps and done multiple searches for specs on specific models for sale without much luck. Are there any sites that have info on pumps that are no longer made but still available on the used market? Are there specific models/brands that are preferred for vacuum chucking? I know Gast and Thomas are good brands, but there must be others that make or made suitable pumps. The variety of pumps for sale is mind boggling, so it would be very helpful to have more info available.