The present invention provides a looseness-prevention screw thread structure including a screw thread having a predetermined pitch, a no-load flank which is an inclined surface in a direction in which the screw thread is advanced, and a load flank which is an inclined surface in a direction in which the screw thread is retracted, the no-load flank and the load flank being formed at both sides of the screw thread, in which the no-load flank of the screw thread includes: a first tangential portion which abuts against an arc portion formed at a thread crest of an opposing fastening object; and a second tangential portion which has a preset angle with respect to the first tangential portion and abuts against the arc portion.

The present invention provides a looseness-prevention screw thread structure including a screw thread having a predetermined pitch, a no-load flank which is an inclined surface in a direction in which the screw thread is advanced, and a load flank which is an inclined surface in a direction in which the screw thread is retracted, the no-load flank and the load flank being formed at both sides of the screw thread, in which the no-load flank of the screw thread includes: a first tangential portion which abuts against an arc portion formed at a thread crest of an opposing fastening object; and a second tangential portion which has a preset angle with respect to the first tangential portion and abuts against the arc portion.

Provided are a control device and a control method for a machine tool which are capable of further reducing a command-waiting time. This control device for a machine tool which controls synchronized operation of a main shaft and a feed shaft comprises: a numerical value control unit; a main shaft control unit; a rotation detection unit. The numerical value control unit has a main shaft command output unit which, when a cutting operation and pulling-out operation are carried out from a machining start position to a target position an arbitrary number of times, acquires from the tapping program the rotation amount and the maximum rotation speed of the main shaft in the cutting operation and pulling-out operation and which supplies the rotation amount and the maximum rotation speed of the main shaft to the main shaft control unit as the main shaft command.

A control device has a master shaft control unit that controls rotation of a master shaft, a slave shaft control unit that controls feeding of a slave shaft, and a numerical value control unit including a master shaft command unit that outputs a first inversion command to the master shaft control unit, a slave shaft command unit that, based on feedback information from the master shaft, outputs a second inversion command that follows the feedback information to the slave shaft control unit, and a prior inversion command unit that outputs a prior inversion command to the slave shaft control unit prior to the output of the first inversion command.

A method for making a screw hole in a workpiece including a plate-shaped portion includes: preparing an auxiliary member having a flat plate shape; forming, in the plate-shaped portion, a first pilot hole having a minor diameter smaller than a major diameter of the screw hole; forming, in the auxiliary member, a second pilot hole having a minor diameter smaller than the major diameter of the screw hole; fixing the auxiliary member to the plate-shaped portion so that the first pilot hole is concentric with the second pilot hole; and making the screw hole in the plate-shaped portion and the auxiliary member by inserting a tap in the first pilot hole and the second pilot hole.

A method includes forming one or more plug holes into a tool surface of a body. The one or more plug holes are partially formed around a landing surface portion of a plug in the body. The method also includes engaging a tool with the landing surface portion of the plug in the body, and using the tool to cut away the plug from the body and at least part of the body to form a tooled void into the body.

A method for producing a workpiece threaded hole by a tapping tool, with a drilling stroke, in which the rotating tapping tool is driven into the workpiece in a drilling direction to a nominal drilling depth, and so forming a thread-free pilot hole, and with a tap-ping stroke in which the tapping tool produces an internal thread in the pilot hole with a tapping feed rate and a tapping speed synchronized therewith. The drilling stroke is followed by a reversing stroke in which the tapping tool is guided out of the pilot hole in a reversing direction opposite to the drilling direction. The tapping tool is then radially displaced by a radial offset in an offset stroke. Then, in the tapping stroke, the radially controlled, rotating tapping tool is guided in a circular rotary motion along a circular path around the hole axis.

A method for producing a workpiece threaded hole by a tapping tool, with a drilling stroke, in which the rotating tapping tool is driven into the workpiece in a drilling direction to a nominal drilling depth, and so forming a thread-free pilot hole, and with a tap-ping stroke in which the tapping tool produces an internal thread in the pilot hole with a tapping feed rate and a tapping speed synchronized therewith. The drilling stroke is followed by a reversing stroke in which the tapping tool is guided out of the pilot hole in a reversing direction opposite to the drilling direction. The tapping tool is then radially displaced by a radial offset in an offset stroke. Then, in the tapping stroke, the radially controlled, rotating tapping tool is guided in a circular rotary motion along a circular path around the hole axis.

In a method for creating a through-thread, thread creation means is moved in a screw-in movement in an axial forward direction (VR) through a workpiece from a first workpiece side to a second workpiece side opposite the first workpiece side such that the end face projects out of the workpiece, wherein the thread creation means is moved through the workpiece, in particular along a first line which is a helical line, wherein then, to create at least one countersink, the thread creation means is moved in a countersinking movement, in particular along a second line that differs from the first line, and wherein, for subsequent withdrawal, the thread creation means is moved back through the workpiece in a screw-out movement in the axial backward direction (RR), in particular at least substantially along the first line.

In a method for creating a through-thread, thread creation means is moved in a screw-in movement in an axial forward direction (VR) through a workpiece from a first workpiece side to a second workpiece side opposite the first workpiece side such that the end face projects out of the workpiece, wherein the thread creation means is moved through the workpiece, in particular along a first line which is a helical line, wherein then, to create at least one countersink, the thread creation means is moved in a countersinking movement, in particular along a second line that differs from the first line, and wherein, for subsequent withdrawal, the thread creation means is moved back through the workpiece in a screw-out movement in the axial backward direction (RR), in particular at least substantially along the first line.