[Problem] To protect a leading end part of a drill having a coolant hole which is adapted for drilling a thin diameter or very thin diameter hole in a workpiece. [Solution] A coolant hole 33 is formed in a shank 3 and a shaft body 7 so as to extend through from a rear end surface 31 of the shank 3 to a leading end surface 15 of the shaft body 7 along an axis thereof. A leading end part of the coolant hole 33 is branched into a pair of discharge holes 35, at a position slightly toward a base end relative to the leading end surface 15 of the shaft body 13. The discharge holes 35 extend in the opposite directions, perpendicular to the coolant hole 33, respectively, and open at opposite side surfaces 37, 37 to define discharge ports 39, 39. A leading end opening 41 of the coolant hole 33 is closed by a bottom face 17 of the drill part 9.

A rotary cutting tool includes a support structure having a central hub located at an axially rearward end of the rotary cutting tool. A plurality of primary support members extends from the central hub in different axial and radial directions in three-dimensional space with respect to a central, rotational axis of the rotary cutting tool. The support structure may include one or more secondary support members extending from a primary support member in different axial and radial directions in three-dimensional space, and one or more tertiary support members to increase stiffness of the support structure. The central hub extends in a plane that is substantially perpendicular to the central, rotational axis of the rotary cutting tool. In one embodiment, each of the plurality of primary support members have a different physical dimension.

Provided is a liquid circulation system including: a shield that covers a boring area of a workpiece in which a hole is bored with a tip of a bit attached to a boring device; a liquid container that holds a liquid; a liquid feeder that forcibly feeds the liquid held in the liquid container to the tip; and a liquid collector that forcibly collects a liquid suspension from an area shielded by the shield and returns the liquid suspension to the liquid container. The liquid circulation system is able to ensure liquid circulation while reliably preventing backflow of the liquid suspension.

A tool holder includes a coolant cavity opening out to a cavity inlet and outlet openings. The coolant cavity includes a cavity upper surface which extends along a cavity central axis. The cavity upper surface includes a cavity widening surface firstly which decreases in distance from the holder peripheral surface and secondly along which the cavity cross-sectional area increases, both with increasing distance from the cavity inlet opening. The cavity upper surface also includes a cavity narrowing surface, located further from the cavity inlet opening than the cavity widening surface, firstly which increases in distance from the holder peripheral surface and secondly along which the cavity cross-sectional area decreases, with increasing distance from the cavity inlet opening. A cutting tool is provided having a cutting insert releasably attached to the tool holder.

A power tool includes a housing, a motor, a spindle, a handle holder and an auxiliary handle. The housing includes a motor housing portion, a drive housing, and a mounting portion between the motor housing portion and the drive housing. The motor is located within the motor housing portion. The spindle is configured to rotate about a rotational axis in response to torque received from the motor. The handle holder is coupled to the drive housing and defines a first mounting point, and the mounting portion defines a second mounting point. The auxiliary handle is selectively attachable to each of the first and second mounting points, and the first mounting point is located at a first position along the rotational axis, and the second mounting point is located at a second position offset from the first position in a direction along the rotational axis.

A tool body includes a damping apparatus having a damper mass body with an axial through bore and a central tube received in the through bore and surrounded by a cavity. An elastic element is arranged on each side of the damper mass body and provided with two socket-like portions extending axially through a central hole of two disc-like members clamping the elastic element therebetween. The socket-like portions project in a rest state of the elastic element extend axially beyond the respective axially directed side of the respective disc-like member and are in an assembled state of the tool body compressed for sealing the cavity with respect to the exterior.

A lubricant material for assisting machining process comprising a polyethylene oxide-polypropylene oxide copolymer having a weight average molecular weight of 5.0×10.sup.4 or more and 2.0×10.sup.5 or less.

A cutting tool comprises at least one cutting edge and at least one relief surface adjacent thereto. The relief surface is arranged to provide clearance behind the cutting edge between the cutting tool and a workpiece and comprises one or more grooves arranged to communicate, in use, a cutting media across the relief surface.

The invention provides a tool holder suitable for cryogenic minimum quantity lubrication, which belongs to the technical field of cooling and lubrication of numerical control machine tools. The device comprises a toolholder body, a peripheral static structure, a multilayer sealing structure, a heat insulation structure, and a bearing support structure. The invention solves the problems of insufficient cooling performance in the micro-lubrication technology and insufficient lubrication in the cryogenic cooling machining technology, and integrates the oxygen insulation protection effect of the cryogenic medium, the cooling effect of the cryogenic medium, and the friction reduction and lubrication effect of the micro-lubrication. It has a good processing effect on difficult-to-cut materials. The invention can be used for machining difficult-to-cut materials with traditional numerical control machine tools, expands the application range of external to internal cooling tool holders, effectively reduces the cutting heat of difficult-to-cut materials in cutting processing, improves tool life, and replaces traditional cutting fluids to achieve green manufacturing.

According to one implementation, a drill includes: a drill includes: a body without a back taper; and a cutting edge part integrated with the body. The body has a flow path of a cutting oil inside. The cuffing edge part has a first supply port that supplies the cutting oil toward a workpiece, The body has at least one second supply port that supplies the cutting oil to a clearance formed between a bush for positioning and the body. The bush is used by being inserted in the body.