I don't have chatter problems when cutting but rigidity is of the utmost importance. The machine you are using and it's column design/fixturing and spindle size needs to be as short/stocky and as large as possible. Then there's the tooling and cutter geometry. You absolutely need carbide pilots and the correct rake on sharp blades. Then there's the speed/feed and operator touch....All factors need to line up. Contact with the chamber is nothing more than the extended top cut and is not the source of chatter IME. J.Rob