Determine standards and varieties
1. Selection principles of varieties:
(1) Considering the working efficiency of processing and assembly, the number of standard parts should be minimized within the same machine or project.
(2) For economic reasons, priority should be given to the selection of commodity standard parts.
(3) According to the expected use requirements of standard parts, the selection of varieties is determined according to type, mechanical performance, accuracy and thread.
2.Type:
(1) Bolts:
① General purpose bolts: there are many varieties, there are hexagonal head and square head, see national standards GB5780-GB5790 and so on.
② Bolts for hinge holes: When using the bolts, insert the bolts tightly into the holes made by the hinge to prevent the workpiece from being displaced. See GB27 and so on.
③ Stop bolt: There are square neck and vertebra, see GB12-15 and so on.
④ Special-purpose bolts: such as T-slot bolts, see GB37; joint bolts, see GB798; foundation bolts, see GB799 and so on.
⑤ Steel structure with high-strength bolted joints: Generally used for friction-type connection of steel structures such as buildings, bridges, towers, pipe supports and cranes, see GB3632 and so on.
(2) Nuts:
① General purpose nuts: mainly refers to hexagon nuts, and square nuts, there are many varieties, see GB41, GB6170-6177 and so on.
② Slotted nut: mainly refers to the hexagonal slotted nut, that is, the top of the hexagonal nut is processed. 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 and so on.
③Lock nut: Refers to the nut with locking function, hex lock nut with nylon insert, see GB889, GB6182, GB6183 and all-metal hexagon lock nut, see GB6184-6187.
④ Special-purpose nuts: such as dish nuts, see GB62; ring nuts, see GB63; cap nuts, see GB802, GB923; knurled nuts, see GB806, GB807, and built-in nuts, see GB809.
(3) Screw:
①Machine screws: There are many types depending on the head shape and groove type. There are several types of head types: cylindrical head, pan head, countersunk head and semi-recessed head. The head is shaped as a slotted slot (slotted bar) and a cross slot. See GB65, GB67-69 and GB818-820.
② Set screw: The set screw uses its tail end to prevent mutual displacement between workpieces and transmit less torque. See GB71, GB73-75, GB77, GB78 and so on.
③ Hex socket screws: Hex socket screws are suitable for occasions where the installation space is small or the screw head needs to be embedded. See GB70, GB6190, GB6191 and GB2672-2674.
④ Special-purpose screws: See GB72, GB828, and GB829 for positioning screws; see GB827-839, GB948, GB948, and eyebolts for screws that do not come out, see GB825.
