Although many screw people have a thorough understanding of the types, shapes, and designs of fasteners, but the studious "screw people" have been looking for knowledge points. I believe that everyone will like this popular science article. , Quickly collect it!
One, determine the category
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.
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 still has a fixed distance function.
⑥ Self-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 it is used, and it 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.

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.
⑶ According to the expected use requirements of standard parts, determine the selection of varieties in terms of type, mechanical properties, precision and thread.
2. Type:
⑴ Bolt:
① General purpose bolts: There are many varieties, including hexagon head and square head.
② Bolts for reaming holes: When using, insert the bolts tightly into the reamed holes to prevent the workpiece from being misplaced.
③ Stop bolt: There are square neck and vertebral points.
④Special purpose bolts: such as bolts for T-slots, see GB37; joint bolts, see GB798; 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, see GB3632, etc.
⑵Nut:
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 above 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锁紧螺母:指具有锁紧功能的螺母,有尼龙嵌件六角锁紧螺母,见GB889、GB6182、GB6183和全金属六角锁紧螺母,见GB6184—6187。
④特殊用途螺母:如碟形螺母,见GB62;环形螺母,见GB63;盖形螺母,见GB802、GB923;滚花螺母,见GB806、GB807和嵌装螺母,见GB809等。
⑶ Screw:
①机器螺钉:因头型和槽型不同而分成许多品种。头型有圆柱头、盘头、沉头和半沉头几种,头部才形为开槽(一字材)和十字槽两种。见GB65、GB67—69及GB818—820等。
②紧定螺钉:紧定螺钉利用其尾端,起防止工件间相互位移及传递较少扭矩的作用。见GB71、GB73——75、GB77、GB78等。
③内六角螺钉:内六角螺钉适用于安装空间较小或螺钉头部需要埋入的场合。,见GB70、GB6190、GB6191和GB2672—2674等。
④特殊用途螺钉:如定位螺钉,见GB72、GB828、GB829;不脱出螺钉,见GB827—839、GB948、GB948和吊环螺钉,见GB825等。
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.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.
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.See GB848, GB95-97 and GB5287.
②Spring (elastic) washers: See GB93, GB859, etc. for spring washers, and GB860, GB955, etc. for elastic washers.
③止退垫圈:有内齿锁紧垫圈,见GB861;外齿锁紧垫圈,见GB862;单耳止动垫圈,见GB854;双耳止动垫圈,见GB855;圆螺母止动垫圈,见GB858等。
④Slanted washer: In order to adapt to the inclination of the supporting surface of the workpiece, an inclined washer can be used.The square bevel washer for I-beam steel, see GB852; the square bevel washer for channel steel, see GB853.
⑹Self tapping screws:
①普通自攻螺钉:螺纹符合GB5280(自攻螺钉用螺纹),螺距大,适合在薄钢板或铜、铝、塑料上使用。见GB845—847、GB5282—5284等。
② Self-tapping locking screw: The thread conforms to the ordinary metric coarse thread, which is suitable for use in occasions that require vibration resistance.See GB6560-6564.
⑺ Rivet:
①Hot-forged rivets: Generally, they have larger specifications and are mostly used in locomotives, ships, and boilers. Usually, hot forging is required to shape the head.See GB863-866.
②Cold-heading forming rivets: Generally, the diameter of the rivet 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.
①圆柱销:有无螺纹圆柱销,见GB119;内螺纹圆柱销,见GB120;外螺纹圆柱销,见GB878;弹性圆柱销,见GB879;带孔圆柱销,见GB880等。
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 bolt with hole and the slotted nut to prevent the bolt and nut from loosening.See GB91.
⑼Retaining ring:
① Retaining ring: Retaining ring with holes.See GB893; 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.
④ Shaft end retaining ring: shaft end retaining ring fastened with screws, see GB891 and shaft end retaining ring fastened with bolts, see GB892.
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 (in-line groove) and cross groove.See GB99-101, GB950-952, etc.
XNUMX. Mechanical performance level
⑴ Bolts, screws, studs and nuts
Ordinary self-tapping screws are not classified according to their mechanical properties. As long as the appropriate specifications are selected, see 3098.5 in GB3.6 and Table 3) to meet their general requirements.
The mechanical performance grades of self-tapping locking screws are divided into two grades: A and B. Grade A is a high-strength grade; Grade B is a low-strength grade.
Fourth, accuracy
Table: Product grade and degree of standard parts (fasteners)
Five, thread
Determine the specifications
① Try to choose a series of values ​​for the diameter specifications, and try not to use the values ​​in parentheses in the product standard size table and the values ​​in the specification table that are not used as much as possible.
②Length specifications generally do not adopt specifications other than those specified in product standards.Generally, when the bolts or nuts are matched and connected, the length of (0.2-0.3)d exposed at the end of the thread is appropriate.
③Specifications with matching diameter and length should be preferred to those within the scope of commodity specifications.