Abstract: A ball-end mill includes arcuate cutting edges each extending from a tip end to a peripherally outermost point along a S shape curve when viewed from the front side, spirally-shaped, peripheral cutting edges each smoothly connected to each arcuate cutting edge, and a convex rake face of each arcuate cutting edge protruding forward in a rotation direction. Each arcuate cutting edge has a radial rake angle satisfying ?<???, where ? is a radial rake angle at a radial angle of 5°, ? is a radial rake angle at a radial angle of 90°, and ? is a radial rake angle at a rotationally most projecting point of the arcuate cutting edge. The radial rake angle has the maximum value at a radial angle in a range of 12-40° and continuously decreases in a range from the rotationally most projecting point to the peripherally outermost point.

Abstract: An indexable ball end mill comprising first to third inserts having arcuate cutting edges detachably attached with first to third screws to first to third seats in a semispherical tip end portion of a tool body; a first threaded hole for the first screw slantingly penetrating a slit-shaped first seat; the first insert having an inclined hole to avoid interference between the first screw and the second and third screws; a hole of the first insert and the first screw having at least partially finished surfaces, so that when the first screw penetrates the first insert attached to the first seat, the first insert is precisely positioned by tight engagement of both finished surfaces.

Abstract: A ball-end mill includes arcuate cutting edges each extending from a tip end to a peripherally outermost point along a S shape curve when viewed from the front side, spirally-shaped, peripheral cutting edges each smoothly connected to each arcuate cutting edge, and a convex rake face of each arcuate cutting edge protruding forward in a rotation direction. Each arcuate cutting edge has a radial rake angle satisfying ?<???, where ? is a radial rake angle at a radial angle of 5°, ? is a radial rake angle at a radial angle of 90°, and ? is a radial rake angle at a rotationally most projecting point of the arcuate cutting edge. The radial rake angle has the maximum value at a radial angle in a range of 12-40° and continuously decreases in a range from the rotationally most projecting point to the peripherally outermost point.

Abstract: An indexable ball end mill comprising first to third inserts having arcuate cutting edges detachably attached with first to third screws to first to third seats in a semispherical tip end portion of a tool body; a first threaded hole for the first screw slantingly penetrating a slit-shaped first seat; the first insert having an inclined hole to avoid interference between the first screw and the second and third screws; a hole of the first insert and the first screw having at least partially finished surfaces, so that when the first screw penetrates the first insert attached to the first seat, the first insert is precisely positioned by tight engagement of both finished surfaces.

Abstract: This aims to provide a ball end mill capable of preventing the occurrence of a ‘pluck’ off a work face. The ball end mill (10) is equipped with two cutting edges (11 and 12) formed at its spherical tips. The rake face (11a) of the cutting edge (11) has its inner circumference end arranged at a position offset farther forward of a rotating direction than a spindle. The rake face (11a) of the cutting edge (11) has its inner circumference end arranged at a position protruding by a predetermined distance from the spindle to the opposite side of the cutting edge forming side in the radial direction. The portion of the cutting edge (11) from a connecting portion (11f), which is formed midway of a ridgeline (11c) or a boundary line between the rake face (11a) of the cutting edge (11) and a flank (11b), to the outer circumference end of the cutting edge (11) is a main cutting edge (11m).

Abstract: This aims to provide a ball end mill capable of preventing the occurrence of a ‘pluck’ off a work face. The ball end mill (10) is equipped with two cutting edges (11 and 12) formed at its spherical tips. The rake face (11a) of the cutting edge (11) has its inner circumference end arranged at a position offset farther forward of a rotating direction than a spindle. The rake face (11a) of the cutting edge (11) has its inner circumference end arranged at a position protruding by a predetermined distance from the spindle to the opposite side of the cutting edge forming side in the radial direction. The portion of the cutting edge (11) from a connecting portion (11f), which is formed midway of a ridgeline (11c) or a boundary line between the rake face (11a) of the cutting edge (11) and a flank (11b), to the outer circumference end of the cutting edge (11) is a main cutting edge (11m).

Abstract: An insert-exchangeable, rotary tool to which throwaway inserts are detachably attached, the insert comprising substantially square-shaped face and bottom surface and an outward curved flank on each side surface, and having a positive-type shape in which an outward curved edge line formed by the face and the flank serves as a cutting edge; each flank having in a substantially center portion a flat surface portion extending to the bottom surface without contacting with the cutting edge; a major cutting edge formed by the outward curved edge line circularly extending from its lowermost point toward a periphery of the tool when the insert is attached to the insert-exchangeable, rotary tool, such that it has a negative radial rake; and the lowermost point being positioned inward a center of the outward curved major cutting edge.

Abstract: An insert-exchangeable, rotary tool to which throwaway inserts are detachably attached, the insert comprising substantially square-shaped face and bottom surface and an outward curved flank on each side surface, and having a positive-type shape in which an outward curved edge line formed by the face and the flank serves as a cutting edge; each flank having in a substantially center portion a flat surface portion extending to the bottom surface without contacting with the cutting edge; a major cutting edge formed by the outward curved edge line circularly extending from its lowermost point toward a periphery of the tool when the insert is attached to the insert-exchangeable, rotary tool, such that it has a negative radial rake; and the lowermost point being positioned inward a center of the outward curved major cutting edge.

Abstract: An indexable type rotary cutting tool (1) has at least one indexable inserts (3, 6). The indexable insert (3, 6) has a main cutting edge (7) and an outer peripheral cutting edge (9). The main cutting edge (7) ranges from 3 to 35 degrees in cutting edge angle, and the main cutting edge (7) is shaped like and arc or a substantially arc, and the outer peripheral cutting edge (8) is shaped like a straight line, an arc, or a substantially arc so as to be back-tapered with respect to a center axis of the tool.

Abstract: A typewriter which has a minimized dimension in the direction of the depth and requires a minimized overall installation area. The typewriter includes a keyboard mounted at a portion near a top, front side of the typewriter housing and is pivotable from and to a horizontal position. When pivoted in a normally closed position, it lies substantially in a plane of a top opening formed in the typewriter housing. The keyboard is located such that its rear end is positioned very close to a platen mounted at a rear portion of the typewriter housing and covers the area of movement of a ribbon cassette carried on a carrier that is mounted to the typewriter housing and moves parallel to the platen.

Abstract: A ribbon feeding mechanism for a typewriter or printer includes a pivotally mounted platform for removably receiving a fabric or carbon ribbon cassette. A manually operable lever carries ribbon feeding components including a toothed wheel for engaging the carbon ribbon takeup unit in the carbon ribbon cassette and a gear for engaging a driven gear of a fabric ribbon cassette. The ribbon feeding components are rotated about a common axis by a cam-driven pawl and rachet mechanism.

Abstract: A drive mechanism for a member to be driven in one direction is disclosed. The mechanism is incorporated in an electronic typewriter and includes a clutch including a clutch spring which provides a driving connection between a small DC motor and the member to be driven of the typewriter. Means is provided which normally holds a driven member of the clutch to a particular angular position and, when the motor is energized, it releases the driven member to allow the driven member to be rotated by the motor. After a cycle of rotation of the driven member, the holding means positively stops rotation of the second element and hence of the driving member and the motor.A new and efficient ribbon feed mechanism is also disclosed which enables selective use of a carbon ribbon and a fabric ink ribbon depending upon a cassette mounted thereon.