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.

Disclosed are threading device and threading method, including a turning step for threading a rotating workpiece with a predetermined cutting depth, by relatively moving a tool in the axial direction of the workpiece and then rounding-up the workpiece obliquely by relatively moving the tool in the axial direction and radially outward. The workpiece is subjected to the threading process by repeatedly carrying out the turning step while sequentially shifting the axial position for starting the rounding-up of the workpiece relative to an axial position where the rounding-up of the workpiece has been started in a previous turning step.

The invention relates to a method of making a thread or tap on a cylindrical, conical or frustoconical piece to be machined.

According to the invention, this method comprises the steps of: a) driving in rotation the piece to be machined in one direction), b) carrying out a relative displacement of a first cutting edge of a tool relative to the piece to be machined until this first cutting edge is flush with the surface to be threaded of the workpiece at the beginning of the section to be threaded, c) carrying out a relative displacement of the tool relative to the piece to be machined so that the first cutting edge machines the piece to be machined, d) carrying out a relative displacement of the tool along the longitudinal axis of the piece to be machined, in one direction until the end of the section to be threaded, e) moving away, by a relative displacement, the first cutting edge of the tool from the piece to be machined,
and it has the particularity of further comprising the steps of: f) reversing the rotation of the piece to be machined to drive this piece in rotation in the direction opposite to the direction, while positioning or not the second cutting edge, g) moving, by relative displacement, a second cutting edge towards the piece to be machined until this second cutting edge penetrates the thread pitch, h) carrying out a relative displacement of the second cutting edge relative to the workpiece so that it continues the machining of the thread in the piece to be machined, i) carrying out a relative displacement of the second cutting edge in a direction opposite to the direction, until the beginning of the section to be threaded, j) moving, by a relative displacement, the second cutting edge away from the workpiece to be machined, k) reversing the rotation of the piece to be machined, while positioning or not the first cutting edge then l) repeating steps b) to k), while continuing the machining of the thread, until the thread reaches its final dimensions, while positioning the first cutting edge in step b) in such a way that it penetrates the thread pitch already machined.

The invention relates to a method of making a thread or tap on a cylindrical, conical or frustoconical piece to be machined.

According to the invention, this method comprises the steps of: a) driving in rotation the piece to be machined in one direction), b) carrying out a relative displacement of a first cutting edge of a tool relative to the piece to be machined until this first cutting edge is flush with the surface to be threaded of the workpiece at the beginning of the section to be threaded, c) carrying out a relative displacement of the tool relative to the piece to be machined so that the first cutting edge machines the piece to be machined, d) carrying out a relative displacement of the tool along the longitudinal axis of the piece to be machined, in one direction until the end of the section to be threaded, e) moving away, by a relative displacement, the first cutting edge of the tool from the piece to be machined,
and it has the particularity of further comprising the steps of: f) reversing the rotation of the piece to be machined to drive this piece in rotation in the direction opposite to the direction, while positioning or not the second cutting edge, g) moving, by relative displacement, a second cutting edge towards the piece to be machined until this second cutting edge penetrates the thread pitch, h) carrying out a relative displacement of the second cutting edge relative to the workpiece so that it continues the machining of the thread in the piece to be machined, i) carrying out a relative displacement of the second cutting edge in a direction opposite to the direction, until the beginning of the section to be threaded, j) moving, by a relative displacement, the second cutting edge away from the workpiece to be machined, k) reversing the rotation of the piece to be machined, while positioning or not the first cutting edge then l) repeating steps b) to k), while continuing the machining of the thread, until the thread reaches its final dimensions, while positioning the first cutting edge in step b) in such a way that it penetrates the thread pitch already machined.

A tool for the chipless production of a thread in a workpiece comprises at least one shaping region which can be rotated about a tool axis (A) for the chipless production or finishing of the thread. The shaping region comprises a plurality of pressing lobes projecting radially outwardly from the tool axis (A) for producing the thread by pressing the pressing lobes into the workpiece surface. The pressing lobes are successively arranged along a forming curve which substantially spirals around the tool axis (A), and the pitch of the forming curve essentially corresponds to the pitch of the thread to be produced or reworked. The forming curve has a helix angle (a), and a profile of at least one pressing lobe is designed in such a way that a thread produced in an axial section containing the tool axis is at least in sections round-arched or ogival.

A tool for the chipless production of a thread in a workpiece comprises at least one shaping region which can be rotated about a tool axis (A) for the chipless production or finishing of the thread. The shaping region comprises a plurality of pressing lobes projecting radially outwardly from the tool axis (A) for producing the thread by pressing the pressing lobes into the workpiece surface. The pressing lobes are successively arranged along a forming curve which substantially spirals around the tool axis (A), and the pitch of the forming curve essentially corresponds to the pitch of the thread to be produced or reworked. The forming curve has a helix angle (a), and a profile of at least one pressing lobe is designed in such a way that a thread produced in an axial section containing the tool axis is at least in sections round-arched or ogival.

A machining method, for a CNC-lathe for forming a predefined thread in a work piece, includes the steps of: rotating the metal work piece around a rotational axis thereof; moving a threading tool along a longitudinal direction through a set of passes, wherein the longitudinal direction is parallel/coinciding to the rotational axis; oscillating the threading tool in a radial direction during a first pass and first frequency, the threading tool moving between a first radial distance (D1) and a second radial distance (D2), (D1) being greater than (D2); oscillating the threading tool in a radial direction during a second pass and second frequency, the threading tool moving between a third radial distance (D3) and a fourth radial distance (D4), (D3) being greater than (D4) and smaller (D1), and (D4) being smaller than (D2); and during a last pass moving the tool without oscillation in the radial direction.

A machining method, for a CNC-lathe for forming a predefined thread in a work piece, includes the steps of: rotating the metal work piece around a rotational axis thereof; moving a threading tool along a longitudinal direction through a set of passes, wherein the longitudinal direction is parallel/coinciding to the rotational axis; oscillating the threading tool in a radial direction during a first pass and first frequency, the threading tool moving between a first radial distance (D1) and a second radial distance (D2), (D1) being greater than (D2); oscillating the threading tool in a radial direction during a second pass and second frequency, the threading tool moving between a third radial distance (D3) and a fourth radial distance (D4), (D3) being greater than (D4) and smaller (D1), and (D4) being smaller than (D2); and during a last pass moving the tool without oscillation in the radial direction.

A machine forms threads on a workpiece by relatively feeding the workpiece and a cutting tool in a feeding direction while relatively rotating the workpiece and the cutting tool, and by performing a helical cutting work multiple times while carrying out relative reciprocal vibration of the workpiece and the cutting tool in a radial direction of the workpiece. The machine tool or a control device of the machine tool includes a vibration setting unit to set a pattern of vibration during each cutting work accompanied by the reciprocal vibration so that a cut portion of one cutting work partially includes a portion that has been cut in another cutting work. The machine tool and the control device prevent a long, continuous chip from becoming entangled with a workpiece or a cutting tool in the process of forming threads on the workpiece.