Ingersoll 1.625, 41.3mm QR Series Quad Twist Drill for Square Inserts, 6108610. Ingersoll Quad Twist Square Insert Indexable Drills for SOMT style inserts. Features 4-cornered economical insert design. Improved machinability due to ideally configured cutting edge. New extended length shanks (R02). RO2 allows two set screw contact for lathe applications and cut-off notch added for ease of shortening in rotating applications.