An apparatus including a lower end fitting having a top planar surface, a bottom planar surface, a counterbore defined therebetween, an opening extending from the counterbore to the top planar surface, and a lock recess that extends both radially outwardly from the counterbore and extends inwardly into the lower end fitting from the bottom planar surface. The apparatus includes a guide tube having a lower end and an end plug configured to connect with the lower end of the guide tube. The end plug has a threaded shaft sized to pass through the opening of the lower end fitting, and a female lock nut has a deformable side wall configured to be swaged into the recess of the lower end fitting. The lock recess remains visible as viewed from the bottom planar surface of the lower end fitting when the female lock nut is fully disposed in the counterbore.

A fuel assembly includes a plurality of fuel rods comprising fissile material, a plurality of guide tubes interspersed amongst the fuel rods, an upper end fitting connected with upper ends of guide tubes, and a lower end fitting. End plugs are connected with the lower ends of the guide tubes. The end plugs have threaded male shafts extending from the lower ends of the guide tubes which pass through openings of the lower end fitting. Female lock nuts are threaded onto the threaded male shafts of the end plugs and lock with the lower end fitting to secure the lower end fitting to the lower ends of the guide tubes. The female lock nuts suitably have locking portions that are outwardly deformed into recesses of the lower end fitting to lock the lock nuts in place after tightening. Dashpot tubes may be disposed in the lower ends of the guide tubes and connected to the end plugs.

A fastener comprises a threaded shank extending along an axis between top and bottom ends and a semi spherical body affixed at the top end of the threaded shank. The fastener further comprises a head having a receptacle adapted to closely surround the semi-spherical body, the head being pivotable about the semi spherical body and rotatably fixed relative to the semi spherical body about the axis of the threaded shank and a drive disposed on the head adapted to receive a tool for rotating the head and the threaded shank about the axis of the threaded shank.

A threaded fastener includes a head end, a shank and an entry end, the head end located at one end of the shank and the entry end located at an opposite end of the shank. The head end includes an end face with a drive recess configured for being driven by multiple drive bit shapes, including a star or six lobe drive, a Phillips drive, a square drive and a flat blade drive.

A threaded fastener is provided that is structured to permit tightening at either the top end (the head) or the bottom end (tip) of the fastener. The fastener comprises a threaded shaft, a head disposed on a first distal end of the threaded shaft, and a tip disposed on a second distal end of the threaded shaft. The tip and the head are structured to fit standard wrenches.

A fuel assembly includes a plurality of fuel rods comprising fissile material, a plurality of guide tubes interspersed amongst the fuel rods, an upper end fitting connected with upper ends of guide tubes, and a lower end fitting. End plugs are connected with the lower ends of the guide tubes. The end plugs have threaded male shafts extending from the lower ends of the guide tubes which pass through openings of the lower end fitting. Female lock nuts are threaded onto the threaded male shafts of the end plugs and lock with the lower end fitting to secure the lower end fitting to the lower ends of the guide tubes. The female lock nuts suitably have locking portions that are outwardly deformed into recesses of the lower end fitting to lock the lock nuts in place after tightening.

A slotted set screw includes a shank, a slot, a cut metal waste storing recess and an outer thread portion. The slot is provided at an end of the shank and includes an opening and a slot bottom surface. The cut metal waste storing recess is provided on the opening of the slot and includes a first vertical wall, a second vertical wall and a horizontal bottom surface. A first horizontal bottom edge connects between the first vertical wall and the horizontal bottom surface while a second horizontal bottom edge connects between the second vertical wall and the horizontal bottom surface. An included angle is formed between the first horizontal bottom edge or the second horizontal bottom edge and a longitudinal axis of the slot less than a right angle. In an embodiment, the bottom surface is lower than a level of the slot bottom surface in a vertical direction.

The invention provides a connection structure including: a first subassembly and a second subassembly each including a first side edge. A first tubular body and a second tubular body are fixedly connected to the first side edge of the first subassembly, and a third tubular body is fixedly connected to the first side edge of the second subassembly; a gap is disposed between the first tubular body and the second tubular body and is configured to accommodate the third tubular body. The connection structure of the invention has a simple and rational design, low production cost, and is easy to assemble and disassemble. The assembly and disassembly of the connection structure can be achieved using conventional tools, without the involvement of operations from professionals, and the connection is highly efficient. The connection structure is particularly practicable for manufacturing different components of jewelry. Through the connection structure, a user can freely combine and match different kinds of jewelry components with each other to form different styles to conform to his or her preferences; in addition, the components of different jewelries can be randomly exchanged as needed, so the connection structure can be used in a broad range of scope.

A recessed head screw includes a shank, a head, a drilling portion and threads. The head includes a top face where a socket portion is formed. The socket portion has a driving recess and a driving socket formed between the driving recess and the top face. The driving socket communicates with the driving recess. A diameter value of the driving socket is a maximum circumscribed circle diameter value of the driving recess plus a value within 20% of the maximum circumscribed circle diameter value. When a driving tool engages the socket portion, the driving socket can be in close-fitting engagement with the driving tool to increase the engagement between the driving tool and the head and prevent the screw from falling off the tool easily during the driving action of the tool, thereby delivering a full driving force to the head to improve the working efficiency and smoothness.

A foreign material exclusion plug is disclosed. The foreign material plug includes a cylindrical body, a slot, and a breakaway tab. The cylindrical body includes an externally-threaded cylindrical structure. The slot is formed in the cylindrical body extending into the cylindrical body from a top surface of the cylindrical body. The breakaway tab is connected to the cylindrical body and extends outwards from the top surface.