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The Basis Of Machining, The Difference And Usage Of Various Types Of Fasteners

Mar 06, 2021

Standard fasteners are divided into ten categories, and the selection should be determined according to the use occasion and function of the standard fasteners.


① Bolts: Bolts are generally matched with nuts (usually add a washer or two washers), and are used for connection and fastening occasions.


②Nut: match the nut with the bolt.


③Screw: The screw is usually used alone (sometimes with a washer), and generally serves as a tightening or tightening function.


④ Stud: 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 the role of fixed distance.


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 usually plays a role of connection or positioning.


⑨ Retaining 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.


Determine standards and varieties


1. The principle of selection 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 performance, precision and thread.


2. Type:


⑴ Bolt:


① General purpose bolts: There are many varieties, including hexagonal head and square head.


② Bolts for reaming holes: When using, insert the bolts tightly into the reamed holes to prevent dislocation of the workpiece.


③ Stop bolt: There are square neck and vertebra.


④Special purpose bolts: such as T-slot bolts, joint bolts, and anchor bolts.


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.


⑵Nut:


①Nuts for general purpose: mainly refers to hexagonal nuts, and there are also square nuts, with many varieties.


②Slotted nut: mainly refers to the hexagonal slotted nut, that is, the groove is processed on the top of the hexagonal nut. It is used in conjunction with a bolt with a hole in the screw and a split pin to prevent the relative rotation of the bolt and the nut.


③Lock nut: refers to a nut with locking function, a hexagonal lock nut with nylon inserts, and an all-metal hexagonal lock nut.


④Special purpose nuts: such as disc nuts, ring nuts, cap nuts, knurled nuts, and embedded nuts.


⑶ Screw:


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. The head shape is slotted (in-line material) and cross-slotted.


②Set screw: The set screw uses its tail end to prevent mutual displacement between the workpieces and transfer less torque.


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.


④Special purpose screws: such as positioning screws, do not come off screws, eyebolts, etc.


⑷ Stud:


①Unequal length double-ended studs: suitable for occasions where one end is screwed into the body of the component for connection or fastening.


②Equal-length double-ended stud: suitable for matching the connecting end and the nut to play the role of connection or distance.


⑸ Washer:


①Flat washers: used to overcome the unevenness of the supporting surface of the workpiece and increase the stress area of the supporting surface.


②Spring (elastic) washer: spring washer, elastic washer.


③ Non-return washers: lock washers with internal teeth; lock washers with external teeth, single-ear lock washers; double-ear lock washers; round nut lock washers.


④Slanted washer: In order to adapt to the inclination of the supporting surface of the workpiece, an inclined washer can be used. Square bevel washers are used for I-beam steel, and square bevel washers are used for channel steel.


⑹Self tapping screws:


①Ordinary self-tapping screws: the thread conforms to (threads for self-tapping screws), with a large pitch, suitable for use on thin steel plates, copper, aluminum, and plastics.


② Self-tapping lock screw: The thread conforms to the ordinary metric coarse thread, which is suitable for use in occasions that require vibration resistance.


⑺ Rivet:


①Hot-forged forming rivets: Generally, they have larger specifications and are mostly used in locomotives, ships, and boilers, etc. The heads are usually formed by hot forging.


②Cold-heading forming rivets: Generally, the diameter of the rivet is ≤16mm, and the head is usually formed by cold heading.


③Hollow and semi-hollow rivets: hollow rivets, semi-hollow rivets, etc.


④Special purpose rivets: headless rivets, tubular rivets, and sign 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 rapid, safe and convenient, and has the advantages of waterproof and anti-leakage.


⑻Sales:


①Cylinder pins: cylindrical pins with or without thread, cylindrical pins with internal threads, cylindrical pins with external threads, elastic cylindrical pins, cylindrical pins with holes.


②Taper pin: with or without thread cylindrical pin, internal thread cylindrical pin, threaded taper pin, taper pin with open end.


③ Split pin: Generally, it is matched with screw bolts with holes and slotted nuts to prevent the bolts and nuts from loosening. .


⑼Retaining ring:


① Retaining ring: Retaining ring with holes. Retaining ring for shaft. Open retaining ring for shaft.


② Wire retaining ring: wire retaining ring for holes, wire retaining ring for shaft, wire locking ring.


③Locking retaining ring for shaft parts: retaining ring locked with taper pin, retaining ring locked with screw, etc.


④Shaft end retaining ring: A shaft end retaining ring fastened with screws, and a shaft end retaining ring fastened with bolts.


⑽Wood screws:


It is divided into many varieties due to different head and trough types. The head type has round head, countersunk head, half countersunk head, etc. The head groove shape is slotted (slotted groove) and cross grooved.