Threaded Connection Assembly Knowledge

Threaded connection is a widely used detachable fixed connection, which has the advantages of simple structure, reliable connection, convenient assembly and disassembly, and is widely used in mechanical equipment.

1. Assembly of stud bolts

Figure 1 Fixing form of stud bolts

1. In order to prevent the bolts from being stuck when they are screwed in, and to facilitate disassembly and repeated installation, lubricating oil can be applied to the stud bolts.

2. The axis of the stud bolt must be perpendicular to the surface of the machine body. Use a square to check during installation. If the axis and the body surface have a slight inclination, you can use a tap to correct the threaded hole, or use the installed stud bolts to correct it; if the inclination is large, do not forcibly correct it to prevent the reliability of the bolt connection from being damaged. .

3. Make sure the connection between the bolts and the body is sufficiently tight.

4. Several common methods of screwing in stud bolts:

① Screw in with two nuts. As shown in Figure 2a), lock the two nuts on the double-ended stud, and then turn the upper nut to screw the double-ended stud into the screw hole.

② Screw in with a long nut. As shown in Figure 2b), the upper screw is used to prevent the relative rotation between the long nut and the double-ended stud, and then the long nut is pulled, and the double-ended stud can be screwed in. The long nut can be removed by loosening the set screw.

Figure 2 The method of screwing in the stud bolts

③ Screw in with a special tool. The picture shows the special tool for screwing in the stud. The three rollers are placed in the cavity of the tool body, and their circumferential and axial positions are determined by the limit sleeve 4. The limit sleeve is fixed by the groove retaining ring, and the loosening and clamping of the roller is controlled by the curve of the inner cavity of the tool. The roller should be clamped on the polished part of the bolt, and the stud bolt can be screwed in by turning the tool body in the direction of the arrow shown in Figure 3, otherwise the bolt can be loosened. The direction of the groove curve of the tool for removing stud bolts shall be opposite to the direction of the curve of the screw-in tool.

Figure 3 Special tool for screwing in stud bolts

(2) Assembly of nuts and screws

1. The surface of the nut or screw and the fastened part should be smooth and flat to avoid additional bending moment when tightening.

2. Strictly control the tightening torque. Excessive tightening torque will elongate or even break the bolt or screw, or cause deformation of the connected parts. When the tightening force is insufficient, the connection is easy to loosen, affecting reliability.

3. After the nut is tightened, the spring washer should be in contact with the nut and the surface of the connected part on the entire circumference. The length of the thread exposed outside the nut should not be less than two buckles, but it should not be too long, generally 3~5mm.

4. When tightening the group nuts, it must be carried out in a certain order and tightened step by step, otherwise the bolts and the body will be deformed due to uneven force. When tightening a group of nuts arranged in a rectangle, it should start from the middle and gradually expand to both sides, as shown in Figure 4. When tightening group nuts arranged in circles or squares, they must be tightened symmetrically, as shown in Figure 5.