Abstract: A portable pneumatic power drill whose tool-carrying spindle is rotated by a pneumatic motor. According to the invention spindle speed is under the control of an electric motor as a function of the speed of rotation of the tool-carrier spindle and of instructions stored in a memory card, control being provided by two microprocessors. This provides operating modularity that is better than that of conventional power drills.

Abstract: A precision twist drill bit provided with two helical teeth separated by grooves. According to the invention, its diameter is equal to the minimum diameter of the hole to be drilled plus 0.005 mm, the width of the land (3) lies in the range 0.1 mm to 0.2 mm, neither tooth is ahead of the other, the end is ground so that it has two slopes with pits (4) that radiate from the center, the cutting edges (1, 2) of the two pits (4) are symmetrical, and all of the surfaces of the drill bit are polished to within an accuracy of less than 0.1 microns Ra.