1. Determine the category
Standard fasteners are divided into ten categories, and the selection should be determined according to the use occasion and function of standard fasteners.
① Bolts: Bolts are generally matched with nuts (usually with a washer or two washers), and are used for connection and fastening occasions.
②Nut: match the nut and bolt.
③Screw: The screw is usually used alone (sometimes with a washer), and it is generally used for tightening or tightening.
④Studs: studs are generally threaded at both ends (single-end studs are threaded at one end), usually one end of the rib is firmly screwed into the body of the component, and the other end is matched with the nut to play the role of connection and fastening , But to a large extent also has a fixed distance function.
⑤ Washer: The washer is placed between the bearing surface of bolts, screws, nuts, etc. and the process bearing surface to prevent loosening and reduce the stress on the bearing surface.
⑥Self-tapping screw: The screw hole of the workpiece matching with the self-tapping screw does not need to be tapped in advance. When the self-tapping screw is screwed in, the internal thread is formed.
⑦ 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 connected piece, and then the end of the rod is riveted to play the role of connection or fastening.
⑧Pin: The pin is inserted into the workpiece when in use, and it usually plays a role of connection or positioning.
⑨Retaining ring: The retaining ring is usually on the shaft or in the hole, and plays the role of limiting the axial direction of the workpiece.
⑩Wood screws: Wood screws are used to screw into wood to connect or fasten.
2. Determine the standards and varieties
1. The selection principle of varieties:
⑴ Considering the efficiency of processing and assembly, in the same machine or project, the variety of standard parts should be minimized.
⑵From economic considerations, product standard parts should be selected first.
⑶ According to the expected use requirements of standard parts, determine the selection of varieties in terms of type, mechanical properties, precision and thread.
① General purpose bolts: There are many varieties, including hexagonal head and square head. See national standards GB5780-GB5790.
② Bolts for reaming holes: When in use, the bolts should be inserted tightly into the reamed holes to prevent dislocation of the workpiece, see GB27, etc.
③ Stop bolt: There are square neck and vertebral points, see GB12-15 etc.
④Special purpose bolts: For example, T-slot bolts, see GB37; joint bolts, see GB798; anchor bolts, see GB799, etc.
⑤ High-strength bolt connection pair for steel structure: generally used for friction-type connection of steel structures such as buildings, bridges, towers, pipeline supports and hoisting machinery, see GB3632, etc.
①General purpose nuts: mainly refers to hexagonal nuts, and there are also square nuts. There are many varieties, see GB41, GB6170-6177, etc.
② Slotted nut: mainly refers to the hexagonal slotted nut, that is, the groove is processed on the hexagonal nut. It is used in conjunction with screw bolts with holes and split pins to prevent the relative rotation of bolts and nuts, see GB6178-6181, etc.
③ Locking nut: refers to the nut with locking function, with nylon insert hexagonal lock nut, see GB889, GB6182, GB6183 and all-metal hexagonal lock nut, see GB6184-6187.
④Special purpose nuts: such as disc nuts, see GB62; ring nuts, see GB63; cap nuts, see GB802 and GB923; knurled nuts, see GB806, GB807 and embedded nuts, see GB809, etc.
①Machine screws: Divided into many varieties due to different head and groove types. There are cylindrical head, pan head, countersunk head and half countersunk head type. The head shape is slotted (in-line material) and cross groove. See GB65, GB67-69 and GB818-820 etc.
②Set screw: The set screw uses its tail end to prevent mutual displacement between the workpieces and transfer less torque. See GB71, GB73—75, GB77, GB78, etc.
③ Hexagon socket screws: Hexagon socket screws are suitable for occasions where the installation space is small or the head of the screw needs to be buried. , See GB70, GB6190, GB6191 and GB2672-2674 etc.
④Special purpose screws: see GB72, GB828, GB829 for positioning screws; see GB827-839, GB948, GB948 and eyebolts, see GB825 for non-stripping screws.
①Unequal length double-ended stud: suitable for occasions where one end is screwed into the body of the component for connection or fastening. See GB897-900 etc.
②Equal-length double-ended stud: suitable for matching the connecting end and the nut to play the role of connection or distance. See GB901, GB953, etc.
①Flat washers: used to overcome the unevenness of the supporting surface of the workpiece and increase the stress area of the supporting surface. See GB848, GB95-97 and GB5287.
②Spring (elastic) washers: See GB93, GB859, etc. for spring washers, and GB860, GB955, etc. for elastic washers.
③ Non-return washers: lock washers with internal teeth, see GB861; lock washers with external teeth, see GB862; single-ear lock washers, see GB854; double-ear lock washers, see GB855; round nut lock washers, see GB858 Wait.
④Slanted washer: In order to adapt to the inclination of the workpiece supporting surface, an inclined washer can be used. For square bevel washers with I-beam, see GB852; for channel steel, see GB853.
⑹Self tapping screws:
①Ordinary self-tapping screws: The thread conforms to GB5280 (threads for self-tapping screws), with a large pitch, suitable for use on thin steel plates, copper, aluminum, and plastics. See GB845-847, GB5282-5284, etc.
②Self-tapping lock screw: The thread conforms to the ordinary metric coarse thread, which is suitable for use in occasions requiring vibration resistance. See GB6560-6564.
①Hot-forged forming rivets: Generally, they have larger specifications and are mostly used in locomotives, ships, and boilers, etc. The head is usually formed by hot forging. See GB863-866.
②Cold-heading forming rivets: the general diameter specification is ≤16mm, and the head is usually formed by cold heading. See GB867-870, GB109, etc.
③Hollow and semi-hollow rivets: hollow rivets, see GB976; semi-hollow rivets, see GB873-875, etc.
④Special purpose rivets: see GB1016 for headless rivets; see GB975 for tubular rivets; see GB827 for label rivets.
⑤ Blind rivet: It is a single-sided riveting rivet. It is a new type of rivet that has been widely used in recent years. It has the characteristics of speed, safety and convenience, and has the advantages of waterproof and leak-proof.
①Cylinder pins: cylindrical pins with or without thread, see GB119; cylindrical pins with internal threads, see GB120; cylindrical pins with external threads, see GB878; elastic cylindrical pins, see GB879; cylindrical pins with holes, see GB880, etc.
②Taper pin: with or without threaded cylindrical pin, see GB117; internal threaded cylindrical pin, see GB118; threaded taper pin, see GB881; taper pin with open end, see GB877.
③ Split pin: Generally, it is matched with the screw with hole bolt and slotted nut to prevent the bolt and nut from loosening. See GB91.
① Retaining ring: Retaining ring with holes. See GB893; elastic retaining ring for shaft. See GB894 and GB896 for shaft opening retaining ring.
② Wire retaining ring: wire retaining ring for holes, see GB895.1; wire retaining ring for shaft, see GB895.2 and wire locking ring, see GB921.
③Locking retaining ring for shaft parts: retaining ring locked with taper pin, see GB883; retaining ring locked with screw, see GB884, GB885, etc.
④Shaft end retaining ring: shaft end retaining ring fastened with screws, see GB891 and shaft end retaining ring fastened with bolts, see GB892.
There are many varieties due to the different head and trough types. The head type has round head, countersunk head, half countersunk head and so on. The head groove shape is slotted (slotted slot) and cross slotted. See GB99-101, GB950-952, etc.