Aluminum sheet comes in 6061-T6 and 3003-H14 alloys. The 6061-T6 is the harder, more machinable aluminum sheet. The 3003-H14 is a softer, more formable aluminum sheet (when drilled and tapped, it is like chewing gum). Note that aluminum sheet thickness is measured in decimal inches up to .190" (3/16") thick.
METAL Pressbrake Bending Tonnage Chart (tons per ft. of bend @ specific die opening / radius) ... Pressbrake Tonnage Chart.xls