An assembled chamfer mill comprises a tool holder, an extension shaft, and chamfer bits locked to two ends of the extension shaft. The chamfer bits each have upper blades and lower blades for chamfering the edges of a workpiece simultaneously. The length of a shaft body of the extension shaft may be set in various sizes. Depending on the thickness and shape of the workpiece, the shaft body having an appropriate length is selected, so as to control the distance between the two chamfer bits. Another extension shaft may be provided to connect a further chamber bit for chamfering the edges of the workpiece simultaneously.

A base material for a hard sintered body includes a pillar portion having a central axis and extending in the axial direction of the central axis. The pillar portion has a first outer peripheral portion, a second outer peripheral portion, and a protruding stripe portion. In the cross-sectional view, one side portion of the first outer peripheral portion extending in a circumferential direction or a radial direction is located inside the other side portion. In the cross-sectional view, one side portion of the second outer peripheral portion extending in the circumferential direction or the radial direction is located outside the other side portion in the radial direction. The protruding stripe portion is located in a connection portion between the other side portion of the first outer peripheral portion and one side portion of the second outer peripheral portion, and protrudes outward.

A cutting tool assembly includes a tool body and a tool holder including a longitudinal axis around which the tool holder is configured to spin. The tool holder includes a central portion connected to the tool body comprising a fastener hole perpendicular with the longitudinal axis and configured to receive a securing fastener, wherein the fastener hole is offset from the longitudinal axis. The tool holder further includes an eccentric drive member connected to the cylindrical portion. The tool holder can optionally further include an end alignment cylinder connected to the eccentric drive member.

A rotary tool can be adapted for removing material from a workpiece such as a lower receiver. A rotary tool can have an adapter with a major diameter, and a cutter head with a minor diameter. The major diameter of the adapter can reduce deflection and chatter, while the minor diameter of the cutter head can be used to manufacture lower receivers with accuracy. The rotary tool can be adapted to be engaged with a rotary power tool.

In this cutting tool with a replaceable cutting head, a cutting head including a cutting edge is detachably attached to a tip end portion of a shaft-like tool main body rotated around an axis in a tool rotation direction. The tool main body and the cutting head are attached to each other when an abutment surface of the tool main body on a tip surface of the tool main body abuts and adheres to an abutment surface of the cutting head on a posterior end surface of the cutting head. A recessed portion and a projecting portion able to be inserted into this recessed portion are respectively formed on the posterior end surface of the cutting head and the tip surface of the tool main body. The recessed portion and the projecting portion are formed to increase in width in a circumferential direction toward an outer peripheral side.

An object of the present invention is to provide a cutting tool that requires the smaller number of parts and can be manufactured at a lower cost. A cutting tool includes: a tool body extending along a central axis and rotatable around the central axis; a cutting insert to be mounted on an insert mounting seat of the tool body; and at least one flow passage provided inside the tool body, the at least one flow passage extending from a back end side toward a front end side of the tool body so as to supply a coolant toward at least a part of the inside of the tool body, a back end side of the at least one flow passage being open at a portion sealed by the tool body and the holding member when the holding member is coupled.

A rotary cutting tool includes a replaceable cutting head and a tool holder. The replaceable cutting head includes a forward cutting portion and a rearward mounting portion. The mounting portion includes a male coupling member that includes a back-tapered conical external thread. The tool holder includes a female coupling member that includes an internal thread. When the rotary cutting tool is in a locked position, the external thread is threadingly engaged with the internal thread.

A rotary tool can be adapted for removing material from a workpiece such as a lower receiver. A rotary tool can have an adapter with a major diameter, and a cutter head with a minor diameter. The major diameter of the adapter can reduce deflection and chatter, while the minor diameter of the cutter head can be used to manufacture lower receivers with accuracy. The rotary tool can be adapted to be engaged with a rotary power tool.

A rotary cutting tool includes a replaceable cutting head and a tool holder. The replaceable cutting head includes a forward cutting portion and a rearward mounting portion. The mounting portion includes a male coupling member that includes an external thread defined by external inner and outer cylinders. The external thread has concavely curved external thread roots which each merge with a respective straight external loaded surface at a first external root point. The first external root point is spaced apart from the external inner cylinder by a first external radial distance. The first external radial distance is greater than a third and less than two thirds of the external thread height. The tool holder includes a female coupling member that includes an internal thread. When the rotary cutting tool is in a locked position, the external thread is threadingly engaged with the internal thread.

An insert may include a base member and a resin layer located on the base member. The base member may include a first surface, a second surface, and a cutting edge. The first surface includes a rake surface region. The second surface may be adjacent to the first surface and includes a flank surface region. The cutting edge may be located in at least a part of a ridge line at which the first surface intersects with the second surface. The resin layer may not be located on the second surface but may be located on the first surface.