Abstract: A dual-threaded screw structure having two kinds of threads formed on a shank, namely, a first thread consisting of one or more threads and a second thread having a lead larger than a lead of the first thread is provided herein. The claimed configuration has a beneficial effect of preventing looseness when the screw structure is fastened with double nuts. One embodiment of the present invention exhibits an example of a dual-threaded screw structure, in which a root diameter between the ridges of the hill-like second thread ridges is formed to be larger by 10% of a height of the ridges than an effective diameter of a first thread. In this case, an inner diameter of an internal thread of a second nut for preventing looseness is formed to be larger than the effective diameter of the first thread by 10% of the height of the ridges.

Abstract: A dual-threaded screw structure having two kinds of threads formed on a shank, namely, a first thread consisting of one or more threads and a second thread having a lead larger than a lead of the first thread is provided herein. The claimed configuration has a beneficial effect of preventing looseness when the screw structure is fastened with double nuts. One embodiment of the present invention exhibits an example of a dual-threaded screw structure, in which a root diameter between the ridges of the hill-like second thread ridges is formed to be larger by 10% of a height of the ridges than an effective diameter of a first thread. In this case, an inner diameter of an internal thread of a second nut for preventing looseness is formed to be larger than the effective diameter of the first thread by 10% of the height of the ridges.

Abstract: The dual-threaded screw structure 1 has a first thread (S1) and a second thread (S2) with various leads formed on the dual-thread portion and has a function of preventing loosening without insufficiency in strength of the dual-thread portion. This dual-thread portion is composed of a first thread (S1) consisting of a coarse thread with a standard pitch P and a specific second thread (S2). The second thread (S2) is formed continuously on the thread ridge of the first thread (S1). The second thread (S2) has a sectional shape of this thread groove same as or substantially same as the first thread (S1), has a same twisting direction as the first thread (S1) and is a multi-threaded thread having threads with a triangular sectional shape and having a lead (L=n*P) a determined number (n)-times of a standard pitch P.

Abstract: The dual-threaded screw structure 1 has a first thread (S1) and a second thread (S2) with various leads formed on the dual-thread portion and has a function of preventing loosening without insufficiency in strength of the dual-thread portion. This dual-thread portion is composed of a first thread (S1) consisting of a coarse thread with a standard pitch P and a specific second thread (S2). The second thread (S2) is formed continuously on the thread ridge of the first thread (S1). The second thread (S2) has a sectional shape of this thread groove same as or substantially same as the first thread (S1), has a same twisting direction as the first thread (S1) and is a multi-threaded thread having threads with a triangular sectional shape and having a lead (L=n*P) a determined number (n)-times of a standard pitch P.

Abstract: A boring such as a high accuracy boring is performed by inputting vibration only in the moving direction of a tool. The device comprises an ultrasonic horn (1) functioning as a vibrator, a punch (2) functioning as a boring tool for boring a work (W) which is an object to be bored, a guide bush (3) guiding the punch (2) in the moving direction, an elastic body (4) for retaining the punch (2) in a floating state on the guide bush (3), and a die (5) functioning as the boring tool formed in pairs with the punch (2). The punch (2) is floatingly retained by the elastic body (4) inside the guide bush (5), and vibration is applied to the punch (2) by the ultrasonic horn (1) to make the punch (2) jump toward the work (W) to strike the work (W) for boring the work (W).

Abstract: A method and apparatus for manufacturing a bolt capable of mass-producing a multiple screw bolt such as a so-called double screw bolt at a low unit price, and a thread rolling die for use therein. The apparatus for manufacturing a bolt comprises a pair of thread rolling dies (1) which are arranged opposite to each other at a predetermined interval, and a bolt supporting unit (2) which supports a cylindrical bolt material (3) in a predetermined position. The thread rolling dies (1) are provided with a transfer pattern (4) having a coarse thread portion (5) which is part of a coarse thread formed by developing a coarse screw, and projections (6) which are part of a fine thread (6a) formed by developing a fine screw as shown by an imaginary line (6a), the fine thread (6a) being formed cyclically on a root portion (5a) of the coarse thread according to a phase shift between the fine thread and the coarse thread.

Abstract: A method and apparatus for manufacturing a bolt capable of mass-producing a multiple screw bolt such as a so-called double screw bolt at a low unit price, and a thread rolling die for use therein. The apparatus for manufacturing a bolt comprises a pair of thread rolling dies (1) which are arranged opposite to each other at a predetermined interval, and a bolt supporting unit (2) which supports a cylindrical bolt material (3) in a predetermined position. The thread rolling dies (1) are provided with a transfer pattern (4) having a coarse thread portion (5) which is part of a coarse thread formed by developing a coarse screw, and projections (6) which are part of a fine thread (6a) formed by developing a fine screw as shown by an imaginary line (6a), the fine thread (6a) being formed cyclically on a root portion (5a) of the coarse thread according to a phase shift between the fine thread and the coarse thread.