Tip: The most critical element, the tip cuts the hole as it pilots the drill through the work piece, producing precision holes in a single pass. The drill’s point, or nose grind, has two basic angles that may be varied for optimum results depending upon the material being drilled. These angles balance cutting forces, distributing them to the tip’s bearing pads to keep the drill concentric. The tip is slightly larger than the shank, so the shank can rotate freely without contacting the hole wall. A round, kidney-shaped, or two round holes through the tip line up with the shank’s channel to allow the flow of coolant at high pressures.

Shank: The shank is made from aircraft grade alloy steel tubing with a110° -120° Vee-flute formed to the center of the shank’s diameter. Coolant is forced from the driver through the center of the shank to the tip, where it is flushed back along the shank’s flute. The shank maintains proper gundrill alignment and must be strong enough to absorb cutting torque and thrust. If the shank is too stiff it may transfer minor mis-alignment in the machine to the tip, but it must not be flexible enough to sag or whip at high RPMs.

Driver: Drivers are cylindrical, with an undercut or flat section for the set screw, which holds in the spindle bore. They are manufactured to industry standards or to special diameters and a concentric hole through the driver’s length allow coolant to pass through to the shank and tip.