PURPOSE: To obtain a drill which is adequate for drilling a hole in any hard material and manufactured easily by forming the cross section perpendicular to the shaft of the drill in the outer periphery thereof in the shape of a polygon which has three angles or more, providing a circular blade groove along outer peripheral torsion, and setting a tip angle to a specific angle.
CONSTITUTION: The cross section perpendicular to the shaft of a drill 11 is formed in a polygon which has three angles or more, and a round blade groove is provided on a main body 11 which has a polygonal column shape. A tip angle θe is set to 130deg. or more. Torsion is provided on the main body 11 which has a polygonal column shape, an edge of the outer periphery which consists of polygonal vertexes of the cross section perpendicular to the shaft on the outer periphery is given roundness and an ultra hard material subjected to coating is used. Since the shape of the cross section perpendicular to the shaft is polygonal, the drill excels in tool rigidity, and tool vibration can be suppressed because it is provided with cutting blade strength owing to the shape of cutting blade, and any damage on the blade tip is reduced. Also, since the edge on outer periphery is inscribed with a virtual cylinder, it has the same effect as a reamer and can provide excellent quality on a machined face.
YOSHITOSHI SHIGEYASU
OKANISHI RYOSUKE
HIGAKI TOSHIHIKO
