A joint device for screw and nut includes a first body and a second body. The first body is provided with a plurality of first internal threads, of first external threads, and a first protrusion. The first protrusion is extended with a first engaging portion. The second body is provided with a plurality of second internal threads, of second external threads, and a second protrusion. The second protrusion is extended with a second engaging portion, such that the first protrusion and the second protrusion can be engaged with each other. When in a joining status, the first engaging portion and the second engaging portion are engaged with each other, such that the first body and the second body are folded up and around the screw. The nut can therefore screw up the first body and the second body correspondingly.

A joint device for screw and nut includes a first body and a second body. The first body is provided with a plurality of first internal threads, of first external threads, and a first protrusion. The first protrusion is extended with a first engaging portion. The second body is provided with a plurality of second internal threads, of second external threads, and a second protrusion. The second protrusion is extended with a second engaging portion, such that the first protrusion and the second protrusion can be engaged with each other. When in a joining status, the first engaging portion and the second engaging portion are engaged with each other, such that the first body and the second body are folded up and around the screw. The nut can therefore screw up the first body and the second body correspondingly.

A bolt of the present invention is a high-strength bolt of high-carbon steel having a tempered martensite structure, wherein the composition of the bolt comprises: 0.50 mass % or more and 0.65 mass % or less of carbon (C); 1.5 mass % or more and 2.5 mass % or less of silicon (Si); 1.0 mass % or more and 2.0 mass % or less of chromium (Cr); 0.2 mass % or more and 1.0 mass % or less of manganese (Mn); and 1.5 mass % or more and 5.0 mass % or less of molybdenum (Mo); a total content of impurities being phosphor (P) and sulfur (S) is 0.03 mass % or more; and the remaining is iron (Fe). Furthermore, the carbon concentration satisfies the following Formula (1): 0.75X<1 . . . Formula (1) wherein, in Formula (1), X represents surface carbon concentration/inner carbon concentration. Therefore, the bolt of the present invention has low quench cracking susceptibility and excellent delayed fracture resistance, because an increase in temperature at which martensite transformation occurs (Ms point) on the surface side is held down.

A bolt of the present invention is a high-strength bolt of high-carbon steel having a tempered martensite structure, wherein the composition of the bolt comprises: 0.50 mass % or more and 0.65 mass % or less of carbon (C); 1.5 mass % or more and 2.5 mass % or less of silicon (Si); 1.0 mass % or more and 2.0 mass % or less of chromium (Cr); 0.2 mass % or more and 1.0 mass % or less of manganese (Mn); and 1.5 mass % or more and 5.0 mass % or less of molybdenum (Mo); a total content of impurities being phosphor (P) and sulfur (S) is 0.03 mass % or more; and the remaining is iron (Fe). Furthermore, the carbon concentration satisfies the following Formula (1): 0.75X<1 . . . Formula (1) wherein, in Formula (1), X represents surface carbon concentration/inner carbon concentration. Therefore, the bolt of the present invention has low quench cracking susceptibility and excellent delayed fracture resistance, because an increase in temperature at which martensite transformation occurs (Ms point) on the surface side is held down.

A set screw for connecting conductors with electrical terminals, such as a terminal block of a load panel includes a screw body and a screw face. The screw face fits inside the screw body and is movable along the axis of the screw body. An elastically deformable member, such as a coil spring or set of spring washers is disposed between the screw body and the screw face. The elastically deformable member compresses in response to force exerted between the screw body and screw face. An indicator bar is connected with the screw face and moves along the axis of the screw body along with the screw face in response to the compressive force. The proximal end of the indicator bar extends proximal of the screw body and includes one or more indicia that show the deformation of the elastically deformable member.

A screw assembly includes a screw and a washer mounted on the screw. The screw includes a screw head, a rotation portion formed on a top of the screw head, and an external thread formed on a bottom of the screw head. The bottom of the screw head is provided with at least one projection and at least one recessed portion. When the external thread is screwed into an article, the washer is compressed between the screw head and the article. The at least one projection and the at least one recessed portion press the washer, and the washer is expanded outward and forms an expansion. The at least one projection and the at least one recessed portion enhance an airtight effect of the washer.

A screw assembly includes a screw and a washer mounted on the screw. The screw includes a screw head, a rotation portion formed on a top of the screw head, and an external thread formed on a bottom of the screw head. The bottom of the screw head is provided with at least one projection and at least one recessed portion. When the external thread is screwed into an article, the washer is compressed between the screw head and the article. The at least one projection and the at least one recessed portion press the washer, and the washer is expanded outward and forms an expansion. The at least one projection and the at least one recessed portion enhance an airtight effect of the washer.

A fluid end having as fluid flow bores sealed without threading a retaining nut into the walls of each bore. The fluid ends may be assembled using a plurality of different kits, each kit comprising a fluid end body, a component, a retainer element, and a fastening system. The retainer element holds the component within each of the bores formed in the fluid end body and the fastening system secures the retainer element to the body. The fastening system comprises a plurality of externally threaded studs, washers and nuts in some embodiments. In other embodiments, the fastening system comprises a plurality of screws.

An axially separable fastener for securing a structure is provided to detach upon command of an electric signal. The fastener includes a metal bolt, an external nut, a frangible ampoule containing a liquid metal eutectic and an internal plug. The bolt has a metal shank with proximal and distal ends. The shank includes a first head at the proximal end, and a first helical external thread and an axial bore with a first helical internal thread at the distal end. The fastener secures a structure in compression between the first head and the external nut. The external nut screws onto the first external thread. The ampoule contains a liquid metal eutectic. The ampoule is insertable into the bore. The internal plug includes a second head, an actuator mechanism, and an auger opposite thereto. The internal plug has a second helical external thread between the second head and the auger for screwing into the bore along the first internal thread. Upon receipt of the signal, the internal plug axially drives the auger towards the proximal end into the ampoule to release the eutectic, thereby fracturing the bolt.

A fluid end having its fluid flow bores sealed without threading a retaining nut into the walls of each bore. The fluid ends may be assembled using a plurality of different kits, each kit comprising a fluid end body, a component, a retainer element, and a fastening system. The retainer element holds the component within each of the bores formed in the fluid end body and the fastening system secures the retainer element to the body. The fastening system comprises a plurality of externally threaded studs, washers and nuts in some embodiments. In other embodiments, the fastening system comprises a plurality of screws.