Abstract: An end mill has a plural number of helical blades formed on the main body of a machine tool. Each of the blades is provided with a plural number of notches spaced along its length and shifted relative to the corresponding notches in the preceding blade. When the notch is shifted to the tool end of the tool, the notch is inclined toward the shank end. On the other hand, when the notches are shifted toward the shank end of the tool, the notches are inclined in the opposite direction, i.e. toward the tool end. Therefore, the wear by rubbing on the side of the blade is diminished, the cutting resistance is decreased and the cutting performance is increased.

Abstract: A ball end mill has a cylindrical tip embedded at the revolving center of the end of the cutter body in the axial direction and one or more arc-shaped flat tips embedded at the end of the cutter body in the radial direction, the former serving as a cutting edge for milling the central part and the latter serving as a cutter edge for milling the peripheral part. Both cutting edges perform uniform milling action and exhibit outstanding durability. The use of throwaway tips extends the life of the tool.