Home Shop Machining/Equipment/Drills

Drilling machine
holding text: the machine that holds and turns the drill bit

Drill Bits
The most common drill bits have a spiral pattern of two flutes down their length which are there to draw the debris out of the hole. The end has two cutting edges but they do not go right to the center. In the middle is a 'chisel edge' where the two cutting edges meet. It cannot cut but just bludgeons the material out of the way which takes more force to push the drill into the material. There are some modifications that can be made here to improve this but at extra cost. It is normally more practical when drilling a hole to start with a small hole, say 3mm (1/8 in) which does not require so much force to push the chisel edge in. Then go up in steps checking the next drill to ensure the chisel edge is not wider than the hole already there. There is a balance between the size and power of the drilling machine and the steps taken but it is not necessary or good practice to take too many steps. It is best to step up as much as possible so that most of the cutting edge of the drill is doing some work, but leave a reasonable amount for the last or final size drill to do. If the final drill is hardly needing to do any cutting the tips may rub rather than cut and become blunt quicker exacerpating the problem.