Standard fasteners are divided into twelve categories, which are determined according to the use of fasteners and their use functions when selected.
1. Bolts
Bolts are widely used in mechanical construction for detachable connections, generally in conjunction with nuts (usually plus one or two washers).
2. Nut
3. Screws
Screws are usually used alone (sometimes with washers), generally play a role in tightening or tightening, and should be screwed into the internal thread of the body.
4. Stud
Studs are mostly used to connect one of the fitted parts with a large thickness, the need to use compact structure or due to frequent disassembly and not suitable for bolted connection. Studs are generally threaded at both ends (single-end studs are single-ended with threads), usually one end of the thread is firmly e into the body of the component, and the other end is matched with the nut, which plays the role of connection and tightening, but to a large extent, it also has the role of fixed spacing.
5. Wooden screws
Wood screws are used to screw into wood and play a jointing or fastening role.
6. Self-tapping screws
The working screw holes that match the self-tapping screw do not require pre-tapping, and the internal thread is formed while screwing in the self-tapping screw.
7. Gasket
Anti-loosening washers
The washer is placed between the support surface of bolts, screws and nuts and the support surface of the workpiece, which plays the role of anti-loosening and reduces the stress of the support surface.
Locking washer
8. Retaining ring
Retaining rings are mainly used to position, lock or stop parts on shafts or holes.
Industrial mesons
9. Pin
Pins are usually used for positioning, can also be used to connect or lock parts, and can also be used for overload shearing elements in safety devices.
10. Rivets
The rivet has a head at one end and the rod is unthreaded. When used, the rod part is inserted into the hole of the connected part, and the end of the rod is riveted after 1 to play a connecting or tightening role.
11. Connecting pair
The connection pair is a combination of screws or bolts or self-tapping screws and washers. When the washer is installed in a screw, it must be able to rotate freely on the screw (or bolt) without falling off. It mainly plays a tightening or tightening role.
12. Others
Mainly including welding nails and other content.
Determine the symbol
(1) The principle of selection of varieties
(1) From the perspective of the work efficiency of processing and assembly, in the same machinery or engineering, the use of fasteners should be minimized;
(2) From economic considerations, the selection of commercial fastener varieties should be preferred.
(3) According to the expected use requirements of fasteners, according to the type, mechanical properties, precision and thread and other > surface to determine the selection of varieties.
(2) Type
(1) Bolts
a) General purpose bolts: there are many varieties, there are hexagonal heads and square heads. Hex head bolt application is the most common, according to manufacturing accuracy and product quality is divided into A, B, C and other product grades, A and B class applications are the most, and mainly used for important, high assembly accuracy and subject to large shock, vibration or variable load places. According to the size of its head support area and the size of the installation position, the hexagonal head bolt can be divided into two types: hexagonal head and large hexagonal head; the head or screw has a variety with holes for the need to lock when it is necessary to use. The square head of the square head bolt has a large size and force surface, which is convenient for the wrench mouth to be stuck or to rely on other parts to stop the rotation, which is often used in relatively rough structures, and sometimes used in the T-shaped groove, which is convenient for the bolt to loosen in the groove to adjust the position. See GB8, GB5780~5790, etc.
b) Bolts for hinged holes: When used, the bolts are tightly embedded into the hinged holes to prevent misalignment of the workpiece, see GB27, etc.
c) Stop rotation bolt: there is a square neck, with mortise, see GB12 ~ 15, etc.;
d) Special purpose bolts: including T-slot bolts, joint bolts and anchor bolts. T-type bolts are mostly used where connections need to be disassembled frequently; anchor bolts are used to fix the frame or motor base in the cement foundation. See GB798, GB799, etc.;
e) High-strength bolted connection pairs for steel structures: Generally used for frictional connections of steel structures such as buildings, bridges, towers, pipeline supports and lifting machinery, see GB3632 and so on.
(2) Nuts
a) General purpose nuts: there are many varieties, there are hex nuts, square nuts, etc. Hex nut with hex bolt is the most common application, according to manufacturing accuracy and product quality is divided into A, B, C and other product grades. Hexagonal thin nuts are used as auxiliary nuts in anti-loosening devices, playing a locking role, or where the threaded connection pair is mainly subjected to shear forces. Hexagonal thick nuts are mostly used in connections that are often disassembled. Square nut and square head bolt are used, the wrench is stuck and not easy to slip, and it is mostly used for rough and simple structures. See GB41, GB6170~6177, etc.;
b) Slotted nut: mainly refers to the hexagonal slotted nut, that is, the slot is processed above the hexagonal nut. It is used in conjunction with screw with hole bolts and open pins to prevent bolts from turning relative to nuts, see GB6178~6181, etc.;
c) Lock nut: refers to the screw with locking function, such as nylon insert hexagonal lock nut and all-metal hexagonal lock nut. Hexagonal nylon ring lock nut has a very reliable anti-loosening ability, in the use of temperature -60 ~ +100 °C and a certain medium conditions, with no damage bolts and connections and can be frequent loading and unloading and other points. See GB889, GB6182~6187, etc.;
d) Special-purpose nuts: such as butterfly nuts, cover nuts, knurled and squat aurisy, fu take 5 nuts can generally be disassembled without tools, usually used in places where the need to be disassembled frequently and the force is not large; the cover nut is used in the place where the end screw needs to be covered. See GB62, GB63, GB802, GB923, GB806, GB807, GB809, etc.
(3) Screws
a) Machine screws: divided into many varieties due to different head types and groove shapes. The head type has several types of cylindrical head, pan head, countersunk head and semi-sink head, and the head groove is generally three kinds of slot (one-word slot), cross groove and hexagonal groove. The cross groove screw is good for neutrality when screwed, the head strength is larger than the word groove, it is not easy to twist bald, and it is generally used in mass production. Hexagonal screws and hexagonal flower screws can apply a large tightening torque, the connection strength is large, and the head can be buried in the body, which is used for the connection of the required compact structure and outer Tang. See GB65, GB67~69 and GB818~820, etc.;
b) Fixing screws: compact screws are used for the relative position of fixed parts, and the head has types such as slotted, hexagonal and square head. The square head can apply a large tightening torque, the top tightening force is large, it is not easy to twist bald, but the head size is large, it is inconvenient to bury in the parts, it is not safe, especially the sports parts are not suitable for use. Slotted, hexagonal ones are easily sunk into parts. According to the different requirements of the use of the screw end, the most commonly used are tapered end, flat end, cylindrical end three. The taper end is suitable for parts with low hardness; when using unspired taper screws, the pit eye should be punched on the top tight surface of the part, and the cone surface should be pressed on the edge of the pit hole. Screws with flat ends, large contact area, do not hurt the surface of the part after top tightening, and are used for occasions where the top tightening hardness is more than that of the titan to correct the position of the worm. The screw at the end of the cylindrical end does not damage the surface of the part, and is mostly used to fix the parts installed on the pipe shaft (thin-walled parts), and the hole on the cylindrical end is pushed into the shaft, and the anti-shear effect of the round end can transmit a large load. See GB71, GB73~75, GB77~78, etc.;
c) Hexagonal screws: Hexagonal screws are suitable for occasions where the installation space is small or the screw head needs to be buried, see GB70, GB6190~6191 and GB2672~2674;
d) Screws for special purposes: such as positioning screws, non-detachable screws and lifting ring screws, see GB72, GB828~829, GB837~839, GB948~949 and GB825.
(4) Studs
a) Unequal length double-head stud: suitable for the occasion of connecting or tightening the body of the component at one end, see GB897~900;
b) Equal length double head stud: suitable for the two ends and the nut to match the connection or fixed spacing. See GB901, GB953, etc.
(5) Wooden screws
There are many varieties due to different head shapes and groove shapes. The head type has several kinds of round head, countersunk head, semi-sink head, etc., and the head groove is slotted (one-word slot) and cross groove, see GB99~101, GB950~952.
(6) Self-tapping screws
a) Ordinary self-tapping screws: the thread conforms to GB5280, the screw pitch is large, suitable for use on thin steel plates or copper, aluminum, plastic, see GB845~847, GB5282~5284, etc.;
b) Self-tapping locking screw: the thread conforms to the ordinary rice coarse tooth thread, suitable for use in the need to resist vibration, see GB6560~ 6564.
(7) Gasket
a) Flat gasket: used to overcome uneven workpiece support surface and increase the stress area of support surface, see GB848, GB95~ 97 and GB5287;
b) Spring (elastic) washer: Spring washer relies on elasticity and bevel friction to prevent the loosening of fasteners, and is widely used in connections that are often disassembled. The inner tooth elastic gasket and the outer tooth elastic gasket have many sharp elastic teeth on the circumference, and the thorn is pressed on the support surface to prevent the loosening of the fastener. The inner tooth elastic washer is used under the screw head with a smaller head size, and 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, and the fasteners are evenly stressed and reliable to prevent loosening, but they should not be used in often disassembled places. See GB93, GB859~860 and GB955;
c) Snap washer: there are inner tooth lock washer, outer tooth lock washer, Gou stop washer, binaural stop washer and round nut with stop washer, etc. Single-ear and two-ear stop washers allow nuts to be tightened in any position to be locked, but it is advisable for fasteners to be at the edge, see GB861~862, GB854~855, GB858, etc.;
d) Inclined washer: In order to adapt to the slope of the working support surface, an inclined gasket can be used. The square inclined washer is used to flatten the inclined surface such as channel steel and I-beam flange, so that the nut support surface is perpendicular to the nail rod, so as to avoid the bending force of the screw when the nut is tightened. See GB852~853 et al.
(8) Retaining ring
a) Elastic retaining ring: the elastic retaining ring for shafts and holes is stuck in the shaft groove or hole slot for rolling bearings to stop and retreat after loading, and there are also open retaining rings for shafts, which are mainly used to be stuck in the shaft groove for part positioning, but cannot withstand axial forces. See GB893~894 and GB896;
b) Steel wire retaining ring: with hole (shaft) steel wire retaining ring and steel wire locking ring. The steel wire retaining ring can also withstand a certain axial force when installed in the shaft groove or hole slot for part positioning. See GB895.1~.2, GB921;
c) Locking ring for shaft parts: The retaining ring locked with a cone pin and the retaining ring locked with screws are mainly used to prevent the axial movement of parts on the shaft. See GB883~892.
d) Shaft end retaining ring: shaft end retaining rings that are screw-tightened and shaft end retaining rings that are bolted, mainly used to lock parts fixed at the shaft end. See GB883~982.
(9) Pin
a) Cylindrical pin: Cylindrical pin is mostly used for fixing parts on the shaft, transmitting power, or as a positioning element. Cylindrical pins are available in different diameter tolerances and can be used with different fit requirements. The B-bar pin is generally fixed in the hole by interference, so it should not be disassembled more. See GB119~120, GB878~880, etc.;
b Cone pin: Cone pin has a taper of 1:50, easy to install on the eye, but also to ensure self-locking, generally used as a positioning element and connecting element, mostly used for frequent disassembly of the place. Female taper pins and screw tail taper pins for holes that do not pass through or in holes where it is difficult to punch pins. The end of the open-tail conical pin can be opened after being punched into the hole to prevent the pin itself from sliding out of the hole. See GB117~118, GB881 and GB877.
Cylindrical pins and various conical pins, generally need to go through reaming processing, after multiple installation and disassembly will reduce the accuracy of positioning and the fastening of the connection, can only transmit a small load. The elastic cylindrical pin itself has elasticity, maintains tension in the hole, is not easy to loosen, is easy to disassemble, and does not affect the nature of the fit, and the pin hole does not need to be hinged. With perforated pins and pin shafts, both for hinge joints;
c) Open pin: The open pin is a anti-loosening device for connecting the machine parts, which is worn into the nut, bolt with pin hole or other pin hole of the connecting part when used, and then the foot is separated. See GB91.
(10) Rivets
a) Hot forging forming rivets: general specifications are larger, mostly used in locomotives, ships and boilers, etc., usually need to be shaped by hot forging, see GB863 ~ 866;
b) Cold heading forming rivets: the general diameter specification of 16mm, usually through cold heading to shape the head, see GB867 ~ 870, GB109 and so on.
c) Hollow and mid-hollow rivets: Hollow rivets are used in places where the shear force is not large, and are often used to connect non-metallic parts such as plastic, leather, wood, canvas and so on.