Abstract: A drill having a pair of cutting edges formed at one end of a shank and arranged symmetrically with respect to a point, each cutting edge comprising a central edge portion and an outer edge portion, the central and outer edge portions each extending substantially straight and being joined to each other with an obtuse angle formed therebetween when seen from below, the central edge portion being formed with a cutting face substantially parallel to the axis of the drill, the land portion of the two edge portions having a top face joined to the cutting face of the central edge portion and curved in a direction to give a large area to the cutting face; a method of grinding the drill with the outer periphery and a side surface of a rotary grinder; and a drill grinding apparatus for practicing the method comprising a holding frame for reciprocatingly moving the drill axially thereof, means for rotating the drill, a disklike rotary grinder, and posture changing means for altering the angle between the grinding porti

Abstract: A drill having a pair of cutting edges formed at one end of a shank and arranged symmetrically with respect to a point, each cutting edge comprising a central edge portion and an outer edge portion, the central and outer edge portions each extending substantially straight and being joined to each other with an obtuse angle formed therebetween when seen from below, the central edge portion being formed with a cutting face substantially parallel to the axis of the drill, the land portion of the two edge portions having a top face joined to the cutting face of the central edge portion and curved in a direction to give a large area to the cutting face; a method of grinding the drill with the outer periphery and a side surface of a rotary grinder; and a drill grinding apparatus for practicing the method comprising a holding frame for reciprocatingly moving the drill axially thereof, means for rotating the drill, a disklike rotary grinder, and posture changing means for altering the angle between the grinding porti

Abstract: A drill having a pair of cutting edges formed at one end of a shank and arranged symmetrically with respect to a point, each cutting edge comprising a central edge portion and an outer edge portion, the central and outer edge portions each extending substantially straight and being joined to each other with an obtuse angle formed therebetween when seen from below, the central edge portion being formed with a central face substantially parallel to the axis of the drill, the land portion of the two edge portions having a top face joined to the central face of the central edge portion and curved in a direction to give a large area to the central face; a method of grinding the drill with the outer periphery and a side surface of a rotary grinder; and a drill grinding apparatus for practicing the method comprising a holding frame for reciprocatingly moving the drill axially thereof, means for rotating the drill, a disklike rotary grinder, and posture changing means for altering the angle between the grinding porti

Abstract: A drill having a shank formed with helical or straight flutes for discharging chips therethrough and a pair of cutting edges formed at one end of the shank and extending continuously from the center of rotation of the drill to the periphery thereof. Each of the flutes is defined by a wall which is positioned rearward with respect to the direction of rotation of the drill and against which a flat plate portion of the chip formed by the portion of the cutting edge on the peripheral side is to be pressed, and by a wall positioned forward with respect to the direction for a side edge portion of the chip to come into contact with. The forward wall is inclined with respect to the rearward wall so as to prevent the chip from curling in its entirety. The drill is given improved rigidity and adapted to discharge chips as broken into fragments of suitable length.

Abstract: A drill having a shank formed with helical or straight flutes for discharging chips therethrough and a pair of cutting edges formed at one end of the shank and extending continuously from the center of rotation of the drill to the periphery thereof. Each of the flutes is defined by a wall which is positioned rearward with respect to the direction of rotation of the drill and against which a flat plate portion of the chip formed by the portion of the cutting edge on the peripheral side is to be pressed, and by a wall positioned forward with respect to the direction for a side edge portion of the chip to come into contact with. The forward wall is inclined with respect to the rearward wall so as to prevent the chip from curling in its entirety. The drill is given improved rigidity and adapted to discharge chips as broken into fragments of suitable length.

Abstract: A cutting edge grinder for grinding the cutting edges of drills includes a center shaft coaxial with a chuck to hold a drill to be ground, a cam attached to the center shaft, a movable frame to hold the center shaft so as to turn freely, a guide member to guide the movable frame in an inclined direction from the center of the center shaft, a turning means to turn the center shaft, and a pressing member to come in contact with the cam face of the cam, such that simple and accurate grinding of curved cutting edges of different shapes is made possible.

Abstract: A drill formed with chip discharging flutes in its shank and having a flute width ratio of 0.5 to 0.02 to give increased torsional rigidity to the drill shank, the drill being adapted to form holes, especially deep holes, with an improved cutting efficiency.

Abstract: This invention relates to an apparatus for grinding the cutting edge flank having special figure of an end mill. This apparatus comprises a grinding part (30) having a grinding wheel (31), a model guide (61) having a guide face (61a) flush with the grinding face of the grinding wheel (31) and arranged to locate under, a cutter support (40), a model support (50) for supporting a model (B.sub.1) parallel with the axial line of the cutter (A) and a shift part (70) for shifting the both support (40), (50) together toward the grinding wheel (31) and the model guide (61). The model (B.sub.1) has the same outer periphery surface as rotary contour outline of the cutter and is provided with a groove (C) so that there is formed a model line (C.sub.1) corresponding to the required cutting edge of the cutter. The cutting edge flank (24) is grinded easily and accurately in imitation of the model (B.sub.1), by turning the cutter and the model solidly in contacting the model (B.sub.

Abstract: A device comprised of a work table, tracing device and cutting device positioned above the table. The work table is capable of holding a workpiece to be cut and a model which serves as a basis for cutting the workpiece to a form identical to that of the model. The tracer includes a spindle and a stylus connected to the bottom of the spindle. The stylus moves against the outer edge of the model and, as it moves, causes the spindle to incline from side to side and displace vertically. Sensors are positioned about the spindle to monitor its movement. The sensors sends signals to the cutter so that the movement of the cutter mirrors the movement of the stylus over the model.