Abstract: An inner cylinder, a pin, and a valve body are movable in a reciprocating manner in a direction along the rotational axis in relation to an oil supply pipe. At a proximate position, where a cutter attaching portion is close to the oil supply pipe, a rod portion of the valve body is supported by a pressure receiving portion of the holder inner cylinder due to the elastic force of a compression coil spring, such that an opening-closing portion of the valve body closes a valve port of the oil supply pipe. At a separated position, where the cutter attaching portion is separated from the oil supply pipe, the rod portion of the valve body is supported by the upper end of the pin due to the elastic force of the compression coil spring, instead of the pressure receiving portion, such that the opening-closing portion opens the valve port.

Abstract: A hole includes a blade cylinder and at least one first blade portion and at least one second blade portion, which are arranged along the rotation direction at intervals. Each of the first and second blade portions includes an inside blade and an outside blade. In the first and second blade portions that are adjacent to each other along the rotation direction, the sum of the number of cutting edges of the outside blade and the cutting edge of the inside blade of the first blade is three or more, the sum of cutting edges of the outside blade and the cutting edge of the inside blade of the second blade is two or more, the number of the cutting edge of the first blade being different from the number of the cutting edges of the second blade.

Abstract: In a state where a rail drilling machine is attached to a rail, a drive source, a cutter support mechanism, and a support base are arranged on one side of the rail. A support plate having an upper support surface and a lower support surface is provided on either end of the support base in the longitudinal direction. The upper support surface and the lower support surface of each support plate contact a lower surface of the rail head and an upper surface of the rail foot, respectively, so that the support base is prevented from moving vertically with respect to the rail. The support base has a magnetic sticking portion located between the support plates. The magnetic sticking portion has a sticking surface that is stuck to a side surface of the rail web.

Abstract: A plurality of blade tips 4, 5 are provided at the distal end of a blade cylinder having a rotation axis. The blade tips 4, 5 are arranged along a rotation direction at intervals. Each of the blade tips 4, 5 has an outside blade 6 at a farther position from the rotation axis and an inside blade 7 at a closer position to the rotation axis. Each outside blade 6 and the corresponding inside blade 7 are arranged next to each other while being displaced in the rotation direction with the stepped cutting edge 8 in between. In the blade tip 4, which is one of the blade tips 4, 5 adjacent to each other in the rotation direction, the sum of the number of the cutting edge 9 in the outside blade 6 and the number of the cutting edges 11, 12 in the inside blade 7 is three. In the other blade tip 5, the sum of the number of the cutting edge 9 in the outside blade 6 and the number of the cutting edge 10 in the inside blade 7 is two.

Abstract: In a state where a rail drilling machine is attached to a rail, a drive source, a cutter support mechanism, and a support base are arranged on one side of the rail. A support plate having an upper support surface and a lower support surface is provided on either end of the support base in the longitudinal direction. The upper support surface and the lower support surface of each support plate contact a lower surface of the rail head and an upper surface of the rail foot, respectively, so that the support base is prevented from moving vertically with respect to the rail. The support base has a magnetic sticking portion located between the support plates. The magnetic sticking portion has a sticking surface that is stuck to a side surface of the rail web.

Abstract: First and second bore blade portions are provided on the outer periphery of a rotary shaft at intervals in the circumferential direction with a rotation axis as the center. A first bore blade portion has a continuous blade and a second bore blade portion has a discontinuous blade having protruding blade edges and indented blade edges, which are alternately provided. The distance in the radial direction of the protruding blade edges is set so as to be greater than or equal to the distance in the radial direction of a continuous blade, and the distance in the radial direction of indented blade edges is set so as to be smaller than the distance in the radial direction of the continuous blade. Accordingly, the cutting resistance of the bore cutter can be reduced.

Abstract: A lock body in a locked state is inserted radially inward of an outer surface. A stopper body in a contact state holds the lock body in an unlocked state. The stopper body in a non-contact state is retracted from the lock body. A pressing body is switchable between a standby state and a retracted state. The pressing body in the standby state selectively contacts a central shaft when an insertion portion is inserted in a support cylinder. The pressing body in the retracted state is retracted from the stopper body. An urging member urges the pressing body into the standby state, and urges the stopper body into the contact state. The urging member detachably engages the pressing body to the stopper body. Thus, the structure of the cutter holder is simple.

Abstract: The front cutting edge is provided with an inner front cutting edge connected with an inner lateral cutting edge and an outer front cutting edge connected with an outer lateral cutting edge. A front flank corresponding to the front cutting edge is provided with an inner front flank corresponding to the inner front cutting edge and an outer front flank corresponding to the outer front cutting edge. An inner front clearance angle of the inner front flank is set at a larger value than an outer front clearance angle of the outer front flank. Therefore, it is difficult for the hole cutter to be chipped, and its cutting performance is also good.

Abstract: A gear transmission device for a power tool. The device transmits rotation of an input shaft to an output shaft, which are coaxially rotated. The input shaft includes a distal portion, and the output shaft includes a basal portion facing towards the distal portion of the input shaft. The gear transmission device includes a support arranged on one of the distal portion of the input shaft and the basal portion of the output shaft. A socket is arranged in the other one of the distal portion of the input shaft and the basal portion of the output shaft. The socket includes a hollow portion for rotatably accommodating the support.

Abstract: First and second bore blade portions are provided on the outer periphery of a rotary shaft at intervals in the circumferential direction with a rotation axis as the center. A first bore blade portion has a continuous blade and a second bore blade portion has a discontinuous blade having protruding blade edges and indented blade edges, which are alternately provided. The distance in the radial direction of the protruding blade edges is set so as to be greater than or equal to the distance in the radial direction of a continuous blade, and the distance in the radial direction of indented blade edges is set so as to be smaller than the distance in the radial direction of the continuous blade. Accordingly, the cutting resistance of the bore cutter can be reduced.

Abstract: The front cutting edge is provided with an inner front cutting edge connected with an inner lateral cutting edge and an outer front cutting edge connected with an outer lateral cutting edge. A front flank corresponding to the front cutting edge is provided with an inner front flank corresponding to the inner front cutting edge and an outer front flank corresponding to the outer front cutting edge. An inner front clearance angle of the inner front flank is set at a larger value than an outer front clearance angle of the outer front flank. Therefore, it is difficult for the hole cutter to be chipped, and its cutting performance is also good.

Abstract: A cutter driving apparatus has a spindle, a base, and a transmission shaft. The spindle has a cutter attached thereto. The base moves along the axis of the spindle. The spindle moves integrally with the base along the axis of the spindle. The base has a pair of support rods. The support rods are disposed apart from the spindle. The transmission shaft transmits a power to the base through the support rods so as to move the base along the axis of the spindle. This structure provides the cutter driving apparatus that facilitates boring operations by boring machines.

Abstract: A slingshot device having an improved target hitting rate. The slingshot device includes a slingshot, which is provided with a front sight and a handgrip, and a releaser, which is provided with a rear sight. The releaser is used to stretch an elastic band of the slingshot. The drawing distance of the elastic band is adjusted by changing the position of the handgrip. The front sight is movable in directions that are perpendicular to the shooting direction of a pellet. The rear sight has a sight slit, which is used to determine the drawing direction of the elastic band.