Drill bit shank The name comes from the German "Stecken – Drehen – Sichern" (Insert – Twist – Secure). In German-speaking countries the back-formation "Spannen durch System" (Clamping System) is used, though Bosch uses "Special Direct System" for international purposes. The triangle shank is almost always made by machining three flats on round bar stock. It is intended as a minor modification of a straight shank, still allowing it to be held in a 3-jaw drill chuck, but allowing higher torque transmission and limited slipping. The Morse taper twist drill bits pictured right are used in metalworking. The full range of tapers is
Down-the-hole drill the drill rods working with a relatively large diameter drill bit caused bore holes to deviate which sometimes meant that a bore hole might finish dangerously close to its neighbour or indeed be closer to the face of the quarry than had been intended. In any event boreholes that are not aligned correctly which are then loaded with high explosive can be extremely dangerous, resulting in rock being projected beyond the intended site. Larger quarries used big rotary machines that required huge amounts of down thrust and high rotation speeds to drive the tri-cone bit hard enough to crush the