An ultrasonic knife has a cutting portion formed with at least one cutting edge and a fastening portion. The fastening portion has an external thread for connection to a sonotrode. The cutting portion and the fastening portion are formed in one piece from cemented carbide material. The cemented carbide material includes hard particles that are, at least predominantly, formed by tungsten carbide and a metallic binder. The external thread of the fastening portion has a thread pitch p and is shaped such that the root of the thread turns has a rounded shape with a root radius R of 0.2*pR0.3*p.

A fastener includes: a shaft having longitudinal axis and a first and second threaded portions, the first and second threaded portions separated by a central portion having a reduced diameter between the first and second threaded portions, and at least one of the first or second threaded portions is chamfered to reduce friction on leading threads.

An apparatus for securing an image sensor within a night vision scope is disclosed. The apparatus includes a flat washer, a crush bushing, and a fastener. The crush bushing is inserted through an opening of a corner anchor of the image sensor. A fastener receptacle is located at a module of the night vision scope. The fastener can be inserted through an opening of the flat washer and a bore of the crush bushing to deform the crush bushing such that the crush bushing material fills any space between the fastener and the fastener receptacle, thereby creating a zero-play connection to restrict any slight movements generated by shocks and vibrations.

To threadedly engage a bolt and a female screw with each other, thereby making it possible to shave off a deposit on the inner surface of the female screw and to make it easy for a worker to sense the seating, there is provided a bolt including a shaft 2 and a head, wherein a first thread 11 is provided on a head side of the shaft, and at least one of a thread provided larger in diameter than the first thread and a thread provided wider than the first thread is provided on a tip end side of the shaft.

A method for tightening a thread joint of a base part with a small thread pitch and a part to be attached with a large thread pitch by rotation in screw-in direction of a differential thread connector, including portions of a one-directional thread corresponding to the threads of the base part and the part to be attached. The differential thread connector can be screwed on the small thread of the base part to a predetermined length, subsequently the part to be attached is screwed on the large thread of the differential thread connector until contact with the base part is reached, and the preliminary tightening is carried out in screw-in direction, and subsequently the differential thread connector is rotated in screw-out direction and the final tightening is carried out.

Inexperienced users of conventional self-drilling drywall anchors may apply too much torque to its screw drive, even after the anchor has become fully bedded down in the drywall, under the mistaken impression that applying a greater torque will improve security of the anchor within the drywall. However, continuing to rotate the anchor after it has been fully inserted into the dry wall continues to rotate the anchor within the drywall and gouges out drywall material from around the anchor. Such gouging causes a cavity to form around the anchor, reducing its security within the wall. The present invention provides a self-drilling drywall anchor having a screw drive 16 that comprises a clutch configured to limit an amount of torque transmitted to the shank 5 by a tool engaged with the screw drive 16. In this way, a user may drive the anchor into a drywall, but over-tightening is prevented as the clutch limits the amount of torque transmitted to the shank 5, thereby preventing the external threads 7 on the shank from gouging out drywall material adjacent to the anchor and reducing the anchor's security within the drywall.

The invention relates to thread joints and can be used in mechanical engineering, equipment construction, the oil and gas industry and communal utility systems.

A method for tightening a thread joint of a base part with a small thread pitch and a part to be attached with a large thread pitch by rotation in screw-in direction of a differential thread connector, comprising portions of a one-directional thread corresponding to the threads of the base part and the part to be attached. The differential thread connector is formed in such a way that it can be screwed on the small thread of the base part to a predetermined length, subsequently the part to be attached is screwed on the large thread of the differential thread connector until contact with the base part is reached, and the preliminary tightening is carried out in screw-in direction, and subsequently the differential thread connector is rotated in screw-out direction and the final tightening is carried out. For instance, the method is applicable for tightening two cylindrical parts, one part 1 with a threaded portion with a pitch S1 and a plane contact surface 4, to another part 2 with a threaded portion with a pitch S2 and a plane contact surface 5, the thread pitch S2 being larger than the pitch S1 by an amount of S=S2S1. A differential thread connector 3 is formed as a coupling with portions with an inner thread with pitches S1 and S2. The method for tightening a thread joint is carried out as follows. The part 1 with the thread pitch S1 is screwed into a threaded aperture of the differential thread joint 3 to a predetermined length A. Subsequently the part 2 with the thread pitch S2 is screwed into the differential thread connector 3 from the opposite end until coupling of the contact surface 5 of the part 2 with the contact surface 4 of the part 1 is reached. In this position the preliminary tightening of the joint with a torque M1 in the direction of the arrow 6 (screw-in) is carried out. Further, while the part 2 is kept immobile, the differential thread connector 3 is rotated around the arrow 7 (screw-out), and the final tightening of the joint is carried out with a torque M2>M1.

A screw having stacked screw heads includes a screw shank portion with a thread and a screw head portion rigidly connected to each other. The screw head portion is driven to bring the screw shank portion to rotate. The screw head portion includes a first screw head and a second screw head. The first screw head has a first shaped groove on its top plane to receive an operating torque. A neck portion is connected to a bottom plane of the first screw head and a top plane of the second screw head. The second screw head has a second shaped groove on its top plane. The neck portion or the connection between the neck portion and the first screw head or the second screw head has lower torsional endurance than each of the first screw head and the second screw head.

A component, provided with a thread has increased play in the axial direction in comparison with a standard thread, which allows nuts to be screwed on, even in the case of highly preloaded bolts, and also enables a highly loadable threaded connection. For this purpose, the play is monotonically increasing in the axial direction.

A high-strength screw (1) includes a head (2) and a threaded portion (5) including a thread (6) and a thread end (9) facing away from the head (2) in an axial direction. The threaded portion (5) includes an unhardened portion (12) starting at the thread end (9) and extending in an axial direction. The unhardened portion (12) has a hardness being reduced compared to an axial middle portion (11) of the threaded portion (5).