A machining device threads a workpiece by relatively rotating the workpiece and a multi-blade tool and relatively moving them along a feed direction to perform cutting processes in the radial direction of the workpiece along the same cutting path in a predetermined spiral form. A controller performs a groove machining to form a threaded portion with vibration in the radial direction of the workpiece and a finish machining to form the threaded portion by bringing the multi-blade tool into contact with the grooved portion of the workpiece. The multi-blade tool has a first cutting blade and a second cutting blade arranged side by side along the feed direction. The controller sets amplitude of a vibration waveform to a value at which a cutting edge of the second cutting blade does not come into contact with the screw bottom surface of the workpiece in the finish machining.

A machining device threads a workpiece by relatively rotating the workpiece and a multi-blade tool and relatively moving them along a feed direction to perform cutting processes in the radial direction of the workpiece along the same cutting path in a predetermined spiral form. A controller performs a groove machining to form a threaded portion with vibration in the radial direction of the workpiece and a finish machining to form the threaded portion by bringing the multi-blade tool into contact with the grooved portion of the workpiece. The multi-blade tool has a first cutting blade and a second cutting blade arranged side by side along the feed direction. The controller sets amplitude of a vibration waveform to a value at which a cutting edge of the second cutting blade does not come into contact with the screw bottom surface of the workpiece in the finish machining.

A lathe includes a spindle, an opposite spindle, a tool post, a controller, and a contact-type breakage detector. The controller determines whether the cut-off tool is broken according to a control parameter for controlling at least one of the spindle and the opposite spindle at a first detection timing immediately after the cut-off tool cuts off the bar material while the opposite spindle holds the bar material held by the spindle. The controller determines whether the cut-off tool is broken according to a detection result by the contact-type breakage detector at a second detection timing different from the first detection timing.

A lathe includes a spindle, an opposite spindle, a tool post, a controller, and a contact-type breakage detector. The controller determines whether the cut-off tool is broken according to a control parameter for controlling at least one of the spindle and the opposite spindle at a first detection timing immediately after the cut-off tool cuts off the bar material while the opposite spindle holds the bar material held by the spindle. The controller determines whether the cut-off tool is broken according to a detection result by the contact-type breakage detector at a second detection timing different from the first detection timing.

A tool head has a longitudinal axis, forward and rearward ends, and top, bottom and peripheral surfaces. The peripheral surface has first and second side walls provided with respective first and second serrated portions, each of the first and second side walls being divided into spaced apart top and bottom side wall portions. The peripheral surface also has a stopper wall which faces in the rearward direction, extends transversely to the second side wall and is provided with a stopper serrated portion. A rear wall formed at the rearward end and connects the first and second side walls. The tool head also includes an insert retaining portion proximate the forward end, and a coupling portion which extends in the direction of the rearward end and includes vertically spaced apart top and bottom coupling arms separated by a coupling recess opening out to the rear wall.

The present disclosure relates to a rhomboid-shaped double-sided turning insert having a convex cutting corner flanked by two flank faces, wherein the insert comprises, on each side: a rhomboid-shaped rake face opposite the face of the opposite side; a lateral cutting corner surface arranged adjoining and between the two flank faces; two flanking edges, each formed between a respective flank face and a rhomboid side of the rake face; a cutting edge formed by a straight primary cutting edge and a straight secondary cutting edge, formed between the lateral cutting corner surface and the rake face, arranged adjoining and between the two flanking edges, wherein the primary cutting edge is longer than the secondary cutting edge; and a chip-deflecting surface which is recessed and arranged inwardly of said cutting edge; wherein a lateral cutting corner surface of the insert, formed by the lateral cutting corner surfaces of a first and a second side, extends between the first side and second side cutting edges, wherein the primary cutting edge and secondary cutting edge are in reversed positions between the first and second sides.

The present disclosure relates to a rhomboid-shaped double-sided turning insert having a convex cutting corner flanked by two flank faces, wherein the insert comprises, on each side: a rhomboid-shaped rake face opposite the face of the opposite side; a lateral cutting corner surface arranged adjoining and between the two flank faces; two flanking edges, each formed between a respective flank face and a rhomboid side of the rake face; a cutting edge formed by a straight primary cutting edge and a straight secondary cutting edge, formed between the lateral cutting corner surface and the rake face, arranged adjoining and between the two flanking edges, wherein the primary cutting edge is longer than the secondary cutting edge; and a chip-deflecting surface which is recessed and arranged inwardly of said cutting edge; wherein a lateral cutting corner surface of the insert, formed by the lateral cutting corner surfaces of a first and a second side, extends between the first side and second side cutting edges, wherein the primary cutting edge and secondary cutting edge are in reversed positions between the first and second sides.

A cutting insert according to an aspect includes a base portion and a cutting portion. The cutting portion includes a front end surface, an top surface, a first lateral surface, a second lateral surface, a front cutting edge, and a lateral cutting edge. The front cutting edge includes a first cutting edge and a second cutting edge, and a radius of curvature of the first cutting edge is greater than a radius of curvature of the second cutting edge.

A cutting insert according to an aspect includes a base portion and a cutting portion. The cutting portion includes a front end surface, an top surface, a first lateral surface, a second lateral surface, a front cutting edge, and a lateral cutting edge. The front cutting edge includes a first cutting edge and a second cutting edge, and a radius of curvature of the first cutting edge is greater than a radius of curvature of the second cutting edge.

A cutting insert may include a base and a cutting part. The cutting part may include an upper surface, a first cutting edge and a second cutting edge. The first cutting edge may be located on a first ridgeline. The second cutting edge may be located on a second ridgeline. The upper surface may include a first inclined surface, protrusions and a first upheaved part. The first inclined surface may be located along the first ridgeline. The protrusions may be located side by side in a direction along the first ridgeline on the first inclined surface. The first upheaved part may be located at a side further away from the first ridgeline than the pair of protrusions. The second cutting edge may be inclined downward. An upper end of the first upheaved part may be located above the second cutting edge.