The tip, at the working end of the drill, is made from a tungsten-carbide alloy, which is much harder and longer lasting than high-speed steel. The head is brazed to a long steel tubing, which is held at it’s other end in the machine chuck. The tip is about 40mm long when new, the cutting edge can be reground until the length of the remaining head is not long enough to act as a guide within the hole. The shorter the tip, the more the risk of wandering.