A rotating cutting tool to cut asymmetrical teeth in a gearwheel in which each tooth (21) has an active flank (A) with a convex profile meshing with the profile of a tooth of an opposing gearwheel meshing with the gearwheel and a secondary concave flank (S), provided with teeth (11) on a generally helical path which extends from one side to the other with respect to a median cross-section (M-M) of the tool which is intended to be intersected by the radius Rp of the gearwheel which is at right angles to the axis of rotation of the tool working on the gearwheel to cut its teeth. The helical teeth have a first flank (CA) which is intended to cut the said active flank (A) of the gearwheel teeth and a second flank (CS) intended to cut the secondary flank (S), the pitch (P1) between the first flank (CA) of the helical teeth being constant and the pitch (P2) of the second flank of the teeth being smaller than the pitch (P1).

A rotating cutting tool to cut asymmetrical teeth in a gearwheel in which each tooth (21) has an active flank (A) with a convex profile meshing with the profile of a tooth of an opposing gearwheel meshing with the gearwheel and a secondary concave flank (S), provided with teeth (11) on a generally helical path which extends from one side to the other with respect to a median cross-section (M-M) of the tool which is intended to be intersected by the radius Rp of the gearwheel which is at right angles to the axis of rotation of the tool working on the gearwheel to cut its teeth. The helical teeth have a first flank (CA) which is intended to cut the said active flank (A) of the gearwheel teeth and a second flank (CS) intended to cut the secondary flank (S), the pitch (P1) between the first flank (CA) of the helical teeth being constant and the pitch (P2) of the second flank of the teeth being smaller than the pitch (P1).

A hob cutter arrangement includes a tool body which has a continuous axial bore, conical bore sections forming both ends of the axial bore, an end shank body at each end of the tool body, and a conical section inserted into the conical bore section. Each end shank body has a radial flange which can be placed against an end face of the tool body and a shaft section on the side of the flange opposite the conical section for clamping in a machine tool. An axle connects the end shank bodies and clamps them together. The end shank bodies are provided with blind holes opening towards the axle and provided with threads to the axle. Elastic elements are clamped between a central section of the axle and a front side of the end shank body on both sides of the axle.

A hob cutter arrangement includes a tool body which has a continuous axial bore, conical bore sections forming both ends of the axial bore, an end shank body at each end of the tool body, and a conical section inserted into the conical bore section. Each end shank body has a radial flange which can be placed against an end face of the tool body and a shaft section on the side of the flange opposite the conical section for clamping in a machine tool. An axle connects the end shank bodies and clamps them together. The end shank bodies are provided with blind holes opening towards the axle and provided with threads to the axle. Elastic elements are clamped between a central section of the axle and a front side of the end shank body on both sides of the axle.

Provided is a coated cutting tool that has a nitride hard coating that contains Ti at 70 at % to 95 at % and Si at 5 at % to 30 at % with respect to the total amount of metallic elements, and Ar at 0.05 at % to 0.20 at % with respect to the total amount of metallic and non-metallic elements, has a NaCl-type crystalline structure, exhibits maximum diffraction peak intensity in the (200) plane, and has an average grain size of 5 nm to 30 nm. When 100 at % is defined as the total of content rates of the metallic elements, nitrogen, oxygen, and carbon in a composition at intervals of 20 nm from a depth of 20 nm to 200 nm from a surface of the hard coating, the content rate of nitrogen is 50.0 at % or more.

A coating film has a lamination unit including a first layer and at least one of a second layer and a third layer. The first layer is a nitride or the like of a first material represented by (Cr.sub.1-a-b-cAl.sub.a[Ni.sub.1-dZr.sub.d].sub.bX.sub.c). X is at least one element selected from Ti, Nb, Si, B, W, and V. a, b, c, and d represent atomic concentrations. The second layer is a nitride or the like of the second material represented by (Al.sub.cCr.sub.1-e-fZ.sub.f). Z is at least one element selected from Si, Y, and B. e and f represent atomic concentrations. The third layer is a nitride or the like of the third material represented by (Al.sub.gCr.sub.1-g).

A machine tool includes a workpiece holder, a tool holder holding working tools that includes a hob cutter used in a rough machining and a skiving cutter used in a finish machining, a tool magazine, a tool replacing device replacing one of the working tools mounted on the tool holder with the other of working tools housed in the tool magazine, a rough machining controlling section performing the rough machining on the workpiece, a tool measuring device measuring a position of a blade in a rotation direction of the skiving cutter, an angle correcting section correcting a rotation angle of the skiving cutter based on a result measured by the tool measuring device, and placing a tooth space formed in the workpiece and an edge tip of the blade in a position corresponding to each other, and a finish machining controlling section by which workpiece is finish machined.

To provide a gear machining apparatus capable of correcting a tooth trace error without using a special tool when a hob cutter is cantilever-supported. A gear machining apparatus includes a hob cutter machining a tooth profile on a workpiece, a tool spindle device rotatably cantilever-supporting the hob cutter, a workpiece spindle device rotatably supporting the workpiece, a driving device moving the tool spindle device and the workpiece spindle device relatively to each other, a measuring device measuring the value corresponding to a bending amount of the hob cutter or a rotation synchronization shift of the workpiece spindle device with respect to the tool spindle device and a correction processing unit correcting a cutting amount of the hob cutter T or the rotation synchronization shift of the workpiece spindle device with respect to the tool spindle device based on the value measured by the measuring device.

Multiple grooves are provided on the outer circumferential surface of the body of an insert holder. A first holding surface of an insert first holding part, which is inserted between a groove bottom and a first protrusion, and a first protrusion surface of the first protrusion make surface contact and said surfaces are sloped so as to approach the groove bottom as the first end is approached. A second holding surface of an insert second holding part, which is inserted between the groove bottom and a second protrusion, and a second protrusion surface of the second protrusion make surface contact and said surface are sloped so as to approach the groove bottom as the second end is approached.

Multiple grooves are provided on the outer circumferential surface of the body of an insert holder. A first holding surface of an insert first holding part, which is inserted between a groove bottom and a first protrusion, and a first protrusion surface of the first protrusion make surface contact and said surfaces are sloped so as to approach the groove bottom as the first end is approached. A second holding surface of an insert second holding part, which is inserted between the groove bottom and a second protrusion, and a second protrusion surface of the second protrusion make surface contact and said surface are sloped so as to approach the groove bottom as the second end is approached.