This is the start of my sheet metal dimpler build. The dimpler I am building is called the DRDT-2 from http://www.experimentalaero.com/DRDT-2.htm. The airplane I am building is flush riveted. The rivets have countersunk heads that must be accommodated by the sheet metal. There are two ways to accomplish this accommodation; dimpling and machine countersinking. The former requires a set of dies and a means of pressing them together with about 3k psi of pressure with your piece of sheet metal between the dies. The latter requires a drill, a microstop cage, and a countersink cutter. Dimpling is best for thinner material and machine countersinking works best for material that is at least .032" thick.