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          Fastener knowledge Daquan hurry to learn it!
          Auther: Pubdate:2018-05-08
          It is necessary for a professional procurement to be described in the national standard.
           
          The standard statement is not with the nut
           
          Screw is commonly known as "screw" with external thread.
           
          The shape is usually hexagon and the inner hole is inner thread. It is used to match the bolts and to tighten the relevant parts.
           
          The nut is commonly known as the "nut".
           
          The head of the bolt is generally hexagonal, and the rod has external thread.
           
          The screw is smaller, the head has flat head and crosshead, and the rod has outer thread.
           
          The studs should be called "double headed studs". Both ends have external threads, and the middle is usually bare rods. One end of the thread is used to connect with the deep hole, and a short section is connected with the nut.

          The standard fasteners are divided into twelve major categories. They are selected according to the use occasion and function of fasteners.
           
          1. bolts: bolts are widely used in mechanical manufacture for detachable connections, usually in conjunction with nuts (usually with a gasket or two gaskets).
           
          2. nut: the nut is used with the bolt.
           
          3. screws: screws are usually used separately (sometimes with gaskets). They usually act as tightening or tightening. They should be screwed into the internal threads of the body.
           
          4. stud: studs are usually used to connect one of the connectors to be large in thickness, and should be constructed with compact structure or unfit for bolt connection because of frequent disassembly. Studs are usually threaded at both ends (single end studs as single end threads), which usually firmly screws into the parts of the body, and the other ends with the nut to connect and fasten, but to a large extent it has a fixed distance.
           
          5. wood screws: wood screws are used to screw in wood for connection or fastening.
           
          6. self tapping screw: the working screw holes matched with the self tapping screws need not be pre tapped, and when the screws are screwed in, the inner threads are formed.
           
          7. washer: the washer is used between bolts, screws and nuts and the supporting surface of the workpiece to prevent loosening and reduce the stress on the supporting surface.
           
          8. retaining ring: the retaining ring is mainly used for positioning, locking or stopping parts on the shaft or hole.
           
          9. pin: pin is usually used for positioning, it can also be used for connecting or locking parts, and can also be used as overload cutting elements in safety devices.
           
          10. rivet: one end of the rivet has a head, and the rod has no thread. When in use, the rod is inserted into the hole of the connecting piece, and then the end of the rod is riveted tightly to form a connection or fastening function.
           
          11. connect the vice connections, that is the combination of screws or bolts or self tapping screws and washers. When the washer is mounted on the screw, it must be free to rotate on the screws (or bolts) without falling off. Mainly fastening or tightening.
           
          12. other main contents include welding nails.
           
          Determination of varieties
           
          (1) the selection principle of varieties
           
          (1) considering the efficiency of processing and assembly, the varieties of fasteners should be minimized in the same machinery or engineering.
           
          Second, from economic considerations, priority should be given to the variety of fasteners.
           
          3. According to the expected use requirements of fasteners, choose varieties according to type, mechanical performance, accuracy and thread.
           
          (2) type
           
          Bolt
           
          A) general purpose bolts: there are many varieties, including six horns and square heads. Six angle head bolt is the most common application. According to the manufacturing precision and product quality, it is divided into A, B, C and other product grades. It is used most in A and B level, and is mainly used for important, high assembly precision and large impact, vibration or variable load.  The six angle head bolts can be divided into six corners and large six angle heads according to the size of the supporting area of the head and the size of the installation position, and the head or screw with a hole with holes is used when the need is locked. The square head of a square head bolt has a larger size and a force surface. It is convenient for the wrench mouth to stop or rest on other parts. It is often used in the rough structure, sometimes used in the T groove, so that the bolt can be loosened and adjusted in the slot. See GB8, GB5780 - 5790 and so on.
           
          B) bolts for reaming holes: when used, bolts are tightly inserted into the reaming holes to prevent workpiece misalignment, such as GB27.
           
          C) check bolts: square neck and tenon, see GB12 ~ 15;
           
          D) bolts for special purposes: including T groove bolts, live bolts and anchor bolts. T groove bolts are often used to be often disconnected; anchor bolts are used for fixed frame or motor base in cement foundation. See GB798, GB799 and so on.
           
          E) steel structure with high strength bolt connection pair: generally used for building, bridge, tower, pipe support and lifting machinery and other steel structures such as friction connection, see GB3632 and so on.
           
          (2) nut
           
          A) general purpose nut: many varieties, including six angle nuts, square nuts and so on. Six angle nuts with six angle bolts are most commonly used. They are classified into A, B and C grades according to their manufacturing accuracy and product quality. The six corner thin nut is used as the auxiliary nut in the loosening device, which acts as a locking force, or is used for threaded joints to mainly bear shear forces. The six corner thick nuts are mostly used for frequent dismantling connections. The square nut is matched with the square head bolt. The spanner is stuck and is not easy to slide. It is used for rough and simple structure. See GB41, GB6170 - 6177 and so on.
           
          B) slotted nut: mainly refers to the six angle slotted nut, that is, processing the groove above the six angle nut. It is used in conjunction with screw hole bolts and pin openings to prevent bolts and nuts from rotating relative to GB6178 to 6181.
           
          C) lock nut: nut with locking function, nylon insert, six angle lock nut and all metal six angle lock nut. The six angle nylon ring locking nut has a very reliable anti loosening ability. It has a point without damaging the bolts and connecting parts and can be frequently loaded and unloaded under the temperature -60 ~ +100 C and a certain medium. See GB889, GB6182 - 6187 and so on.
           
          D) nuts for special purposes: butterfly nut, cover nut, knurled nut and embedded nut. A butterfly nut is usually disassembled without a tool, usually used for often dismantling and small force; a cover nut is used in a place where the end screw needs to be covered. See GB62, GB63, GB802, GB923, GB806, GB807, GB809 and so on.
            Screw
           
          A) machine screws: they are divided into many varieties because of their different head shape and groove shape. The head type has cylindrical head, pan head, sunken head and semi sunken head, and the groove of the head is usually three kinds of slotting (one slot), cross groove and inner six corner slot. The cross groove screw is good for neutral when it is screwed. The head strength is bigger than that of the one slot, and it is not easy to be screwed. It is usually used in mass production. The internal six angle screws and the inner six corner floral screws can exert a large tightening torque. The connection strength is large and the head can be embedded in the body. It is used for the connection where the structure is compact and the shape is smooth. GB65, GB67 to 69 and GB818 ~ 820, etc.
           
          B) fastened screws: fixed screws are used for relative position of fixed parts, and the head has a type of slot, inner six corners and square heads. The square head can apply large tightening torque, the top tightened force is large, and the head is not easy to turn bald, but the head size is large, it is inconvenient to be embedded in the parts, not safe, especially the moving parts should not be used. The one with six grooves and one inside is easy to sink into the parts. According to the different requirements, there are three commonly used tapered screw ends: cone end, flat end and cylindrical end. The cone ends are suitable for parts with small hardness. When using the tapered end screws without sharp points, holes should be made on the top surface of the parts, and the cones should be pressed on the sides of the holes. The screw with a flat end end has a large contact area and does not damage the surface of the part after tightening. It is used for occasions with high rigidity and regular adjustment positions. The screws at the end of the cylinder end do not damage the surface of the parts, and are used to fix the parts mounted on the shaft (Bo Bijian). GB71, GB73 - 75, GB77 - 78 and so on.
           
          C) six angle screws: six angle screws are suitable for occasions where the installation space is small or the screw heads need to be embedded. See GB70, GB6190 ~ 6191 and GB2672 ~ 2674;
           
          D) screws for special purposes: for positioning screws, non lifting screws and lifting screws, see GB72, GB828 ~ 829, GB837 ~ 839, GB948 ~ 949 and GB825.

          Stud
           
          A) unequal length stud stud: suitable for one end to screw in the part of the body to connect or tighten the function, see GB897 ~ 900;
           
          B) equal length stud stud: suitable for connecting ends or nuts to connect or fixed distance. See GB901, GB953 and so on.
           
          Wooden screw
           
          It is divided into many varieties because of different head type and groove. The head type has round head, sunken head and half sunken head, etc. the head groove is two kinds of slotting (one slot) and cross groove, see GB99 to 101, GB950 to 952.
           
          Self tapping screw
           
          A) plain self tapping screw: thread fit GB5280, large pitch, suitable for use on thin steel plate or copper, aluminum and plastic, see GB845 ~ 847, GB5282 ~ 5284;
           
          B) self attack locking screw: thread is in line with common metric coarse thread, suitable for use in vibration resistant occasions. See GB6560 to 6564.
           
          A gasket
           
          A) plain washer: to overcome the uneven surface of the workpiece and increase the stress area of the supporting surface, see GB848, GB95 ~ 97 and GB5287;
           
          B) spring (elastic) washer: spring washer depends on elastic and diagonal friction to prevent loosening of fasteners, and is widely used for frequently dismantled connections. The inner tooth elastic washer and the outer tooth elastic washer have many sharp elastic teeth on the circumference of the outer tooth, and the needling on the supporting surface can prevent the fasteners from loosening. The inner tooth elastic washer is used for the screw head with smaller head size; the outer tooth elastic washer is mostly used under the bolt head and nut. The elastic washer with teeth is smaller than the ordinary spring washer, the force of the fastener is uniform and the loosening is reliable, but it is not suitable for the usual disassembly place. See GB93, GB859 to 860 and GB955;
           
          C) check washer: there are inner teeth locking washers, outer teeth locking washers, single ear locking washers, double ear washers and locking washers for round nuts. Single - ear and double - ear stop washer allow nut tightening to be locked at any position, but the fasteners should be on the edge, see GB861 - 862, GB854 - 855, GB858 and so on.
           
          D) oblique washer: oblique washer can be used in order to fit the slope of working supporting surface. The square washer is used to pad the inclined surface of the channel steel and I-beam flange to make the supporting surface of the nut perpendicular to the nail bar, so that the screw can not be flexed when tightening the nut. See GB852 to 853.
          Retaining ring
           
          A) elastic retaining ring: the elastic retaining ring for shaft and hole is used in the shaft slot or slot for rolling bearings to be loaded back and back. In addition, the shaft is used as the opening ring. It is mainly used for the positioning of the parts in the shaft slot, but can not bear the axial force. GB893 to 894 and GB896;
           
          B) steel wire retaining ring: there are Kong Yong (shaft) steel wire retaining rings and steel wire lock rings. The steel wire retaining ring is installed in the shaft slot or hole slot for parts to be positioned, and it can also bear a certain axial force. GB895.1 to.2 and GB921;
           
          C) locking rings for shaft parts: locking pins with useful tapered pins and locking rings with screws, mainly used to prevent axial movement of shaft parts. See GB883 to 892.
           
          D) shaft end retaining ring: shaft end retaining ring fastened by useful screws and shaft end retaining ring fastened by bolts, mainly used for locking parts fixed at the shaft ends. See GB883 to 982.
           
          Pin
           
          A) cylindrical pin: the cylindrical pin is mostly used for fixing parts on the shaft, transmitting power or positioning elements. The cylindrical pin has different diameter tolerances, which can be used for different matching requirements. The cylindrical pin is usually fixed in the hole by interference, so it is not suitable to be demolished. GB119 - 120, GB878 - 880 and so on.
           
          B conical pin: conical pin has the taper of 1:50, easy to install eye, also guarantee self lock, usually used as positioning element and connection element, more used for frequently dismantling places. Internal thread conical pin and screw tail cone pin are used for holes without holes or for holes in pins that are difficult to pin out. The open end taper pin is inserted into the hole, and the rear end can be opened to prevent the pin itself from sliding out of the hole. See GB117 ~ 118, GB881, GB877 and so on.
           
          Cylindrical pin and pin holes of all kinds of conical pins are generally processed by hinged holes. After multiple loading and dismantling, the precision of positioning and fastening of the connection can be reduced, and only a small load can be passed. The elastic cylindrical pin itself is elastic, and has a tension in the hole, which is not easy to release, and is convenient to disassemble, and does not affect the matching property. The pin hole does not need to be reamed. The pin and pin shaft are used for hinge joints.
           
          C) opening pin: the opening pin is an anti loosening device for connecting the machine. It is used in the nut, the bolt with the pin hole or the pin hole of the other connector, and then the foot is separated. See GB91.
           
          Rivet
           
          A) hot forging rivets: the general specifications are large, and are usually used for locomotives, ships and boilers, etc., usually by hot forging to form the head, see GB863 ~ 866;
           
          B) cold heading forming rivet: the general diameter specification 16mm, usually through cold heading to form the head, see GB867 ~ 870, GB109 and so on.
           
          C) hollow and semi hollow rivets: hollow rivets are often used to connect non-metallic parts such as plastics, leather, timber, canvas and so on.

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