Standard fasteners are divided into twelve categories, and the selection is determined according to the use occasions and functions of the fasteners.
Bolts are widely used in detachable connections in mechanical manufacturing, and are generally used in conjunction with nuts
Screws are usually used alone (sometimes with washers), generally for tightening or tightening, and should be screwed into the internal thread of the body.
Studs are mostly used to connect one of the connected parts with a large thickness and need to be used in places where the structure is compact or the bolt connection is not suitable due to frequent disassembly. Studs are generally threaded at both ends (single-headed studs are threaded on one end), usually one end of the thread is firmly inserted into the body of the component, and the other end is matched with the nut, which plays the role of connection and tightening, but in the To a large extent also has the role of distance.
5. Wood screws
Wood screws are used to screw into wood for connection or fastening.
6. Self-tapping screws
The working screw holes matched with the self-tapping screw do not need to be tapped in advance, and the internal thread is formed at the same time as the self-tapping screw is screwed in.
Washers are used between the supporting surface of bolts, screws and nuts and the supporting surface of the workpiece to prevent loosening and reduce the stress of the supporting surface.
8. retaining ring
The retaining ring is mainly used to position, lock or stop the parts on the shaft or in the hole.
Pins are usually used for positioning, but also for connecting or locking parts, and as overload shearing elements in safety devices.
The rivet has a head on one end and no thread on the stem. When in use, the rod is inserted into the hole of the connected piece, and then the end of the rod is riveted for connection or fastening.
11. Connection pair
The connection pair is a combination of screws or bolts or self-tapping screws and washers. After the washer is installed on the screw, it must be able to rotate freely on the screw (or bolt) without falling off. Mainly play the role of tightening or tightening.
It mainly includes welding studs and so on.
Determine the variety
(1) Principles of selection of varieties
① Considering the efficiency of processing and assembling, in the same machinery or project, the variety of fasteners used should be minimized;
② From economic considerations, the variety of commodity fasteners should be preferred.
③ According to the expected use requirements of the fasteners, the selected varieties are determined according to the type, mechanical properties, precision and thread surface.
a) General purpose bolts: There are many varieties, including hexagonal head and square head. Hexagon head bolts are the most common application, and are divided into A, B, C and other product grades according to manufacturing accuracy and product quality, with A and B grades being the most widely used, and are mainly used for important, high assembly accuracy and those subject to greater impact, vibration or where the load changes. Hexagon head bolts can be divided into two types: hexagonal head and large hexagonal head according to the size of the head support area and the size of the installation position; the head or screw has a variety with holes for use when locking is required. The square head of the square head bolt has a larger size and a stress surface, which is convenient for the wrench mouth to be stuck or lean against other parts to prevent rotation. Loose adjustment position in slot. See GB8, GB5780～5790, etc.
b) Bolts for reaming holes: when in use, the bolts are tightly inserted into the reaming holes to prevent the dislocation of the workpiece, see GB27, etc.
c) Anti-rotation bolts: There are square neck and tenon, see GB12~15, etc.;
d) Special purpose bolts: including T-slot bolts, joint bolts and anchor bolts. T-type bolts are mostly used in places that need to be disconnected frequently; anchor bolts are used to fix the frame or motor base in the cement foundation. See GB798, GB799, etc.;
e) 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.
a) General purpose nuts: There are many varieties, including hexagonal nuts, square nuts, etc. Hexagon nuts and hexagon bolts are most commonly used, and are classified into product grades A, B, and C according to manufacturing accuracy and product quality. Hexagonal thin nuts are used as auxiliary nuts in anti-loosening devices, which play a locking role, or are used in places
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