A method of machining a screw is provided that is capable of preventing formation of a protruding section at a thread tip section. A thread is formed by cutting on a cylindrical body, and a surface of the thread is plastically deformed by rolling. Because of the cutting, a width between-side surfaces of a thread tip section is in a narrowed state as compared to a normal width. This width is narrowed toward a tip of the thread while a thread body section has a width expanded as compared to a normal width. Consequently, the side surfaces are formed to bulge by an excess thickness portion as compared to normal side surfaces. The rolling plastically deforms both side surfaces to cause the excess thickness portion to plastically flow toward the side surfaces.

A method of machining a screw is provided that is capable of preventing formation of a protruding section at a thread tip section. A thread is formed by cutting on a cylindrical body, and a surface of the thread is plastically deformed by rolling. Because of the cutting, a width between-side surfaces of a thread tip section is in a narrowed state as compared to a normal width. This width is narrowed toward a tip of the thread while a thread body section has a width expanded as compared to a normal width. Consequently, the side surfaces are formed to bulge by an excess thickness portion as compared to normal side surfaces. The rolling plastically deforms both side surfaces to cause the excess thickness portion to plastically flow toward the side surfaces.

A method of creating an NC program for threading includes: a first step of setting a position in the NC program at which a G code or an M code is to be inserted; a second step of making a setting for applying a vibration component in a thread radial direction to a tool movement path; and a third step of, based on an instruction for reflecting the setting made in the second step in the NC program, inserting at the position in the NC program the G code or the M code for applying the vibration component in the thread radial direction, thereby creating the NC program for threading.

A headstock assembly for a machine tool includes a mount having a female threaded bore, a headstock mounted slidably relative to the machine base, a drive member mounted on the headstock, a spindle, and a spindle extension. The spindle has an intermediate segment disposed in a chamber of the headstock and coupled to be driven by the drive member so as to permit the spindle to rotate about a spindle axis. The spindle extension is coupled to be rotatable with the spindle, and has a male threaded segment configured to be in threaded engagement with the female threaded bore so as to permit the headstock to be linearly moved relative to the mount.

A numerical control apparatus includes: a drive unit controlling a main shaft rotating a workpiece, a first drive shaft feeding a cutting tool relatively to the workpiece along a perpendicular direction to a lead direction of a thread, and a second drive shaft feeding the cutting tool relatively to the workpiece along the lead direction; and a vibration unit superimposing, on movement of the first drive shaft, vibration having a period having a predetermined ratio with a rotation period of the main shaft, and forms a thread on the workpiece by moving the cutting tool and the workpiece relative to each other and performing cut processes on the workpiece. The numerical control apparatus includes a thread-cutting vibration adjustment unit controlling the drive unit to shift phase of the vibration with respect to phase of the main shaft by a predetermined vibration phase shift amount every time in the cut processes.

A method of converting a tubular having NC46 connections to CET43 connections. A method of applying a CET43 thread to a pin connection or a box connection or both. A box connection and a pin connection of the tubular are machined and a CET43 thread applied to the box connection and the pin connection.

A headstock assembly for a machine tool includes a mount having a female threaded bore, a headstock mounted slidably relative to the machine base, a drive member mounted on the headstock, a spindle, and a spindle extension. The spindle has an intermediate segment disposed in a chamber of the headstock and coupled to be driven by the drive member so as to permit the spindle to rotate about a spindle axis. The spindle extension is coupled to be rotatable with the spindle, and has a male threaded segment configured to be in threaded engagement with the female threaded bore so as to permit the headstock to be linearly moved relative to the mount.

A turning and thread-rolling machine with a pre-compression device includes a fixing base on which the pre-compression device, a fixing mechanism, a guiding base, a processing mechanism assembly, and a control unit are provided, wherein the pre-compression device includes a carrier and at least two cold-rolling heads in order to form by compression a pre-compressed annular groove in a portion of an unprocessed rebar that is adjacent to one end thereof, and, under the control of the control unit, the fixing mechanism clamps the rebar, and the guiding base displaces the processing mechanism assembly to the end of the rebar to perform turning and thread rolling sequentially, thereby processing the end of the rebar into a coupling end. The pre-compressed annular groove facilitates on-site inspection of thread quality and prevents the thread-rolling dies in the processing mechanism assembly from contact with, and hence damage by, the ribs on the rebar.

A turning and thread-rolling machine with a pre-compression device includes a fixing base on which the pre-compression device, a fixing mechanism, a guiding base, a processing mechanism assembly, and a control unit are provided, wherein the pre-compression device includes a carrier and at least two cold-rolling heads in order to form by compression a pre-compressed annular groove in a portion of an unprocessed rebar that is adjacent to one end thereof, and, under the control of the control unit, the fixing mechanism clamps the rebar, and the guiding base displaces the processing mechanism assembly to the end of the rebar to perform turning and thread rolling sequentially, thereby processing the end of the rebar into a coupling end. The pre-compressed annular groove facilitates on-site inspection of thread quality and prevents the thread-rolling dies in the processing mechanism assembly from contact with, and hence damage by, the ribs on the rebar.

The present invention discloses a method of constructing a high-frequency vibratory stress relief device for eliminating residual stress of a small work-piece. The method comprises the following steps: fabricating a high-frequency vibration energy amplification device; fabricating a clamping device; mounting the high-frequency vibration energy amplification device; obtaining surface residual stress distribution on the small work-piece by means of X-ray diffraction; establishing a finite element model of the small work-piece; determining a target frequency f, determining the structural dimensions of the high-frequency vibration energy amplification device; analyzing the displacement mode to obtain loci of the vibration node lines and number of the vibration node lines; clamping the small work-piece; attaching strain gauges; connecting all devices. The present invention has the advantage of being able to increase the vibration energy acting on the small work-piece to achieve a better effect of high-frequency vibratory stress relief.