Malentendido del uso de pieza de fijación

Actualizar:28-07-2020
Resumen:

Fasteners are very widely used connection parts in our […]

Fasteners are very widely used connection parts in our lives, but we will encounter some misunderstandings in the process of use. In response to these problems, the following are summarized.

1. Use coarse teeth instead of fine teeth

There are many important connections on the machine, such as drive shafts, and most of the bolts are fine thread. If there are missing parts during maintenance, some maintenance personnel will use coarse bolts instead, which should be avoided.

Because the inner diameter of the fine pitch bolt is larger, the pitch and outer angle are smaller, the strength is high, the self-locking performance is good, and the ability to withstand impact, vibration and exchange loads is relatively strong. Once replaced with coarse-threaded bolts, it is easy to loosen or fall off, disassemble, and even cause mechanical accidents.

2. Pore is not matched

The bolts on the machine that bear the lateral load and shearing force, such as the drive shaft bolts and flywheel bolts, are in transitional fit with the bolt holes. The assembly should be strong and reliable and able to withstand lateral forces.

Someone does not pay attention to the inspection during the assembly process, and the installation continues when there is a large gap between the bolt and the bolt hole, which is prone to bolt loosening or cutting accidents.

3. Thicken nuts increase connection reliability

Some people mistakenly believe that thickening the nut can increase the number of working turns of the thread and improve the reliability of the connection. But in fact, the thicker the nut, the more uneven the load distribution between the threads of each circle, and the easier the connection piece to loosen.

4. Tighten it tightly

Many people think that bolts should be “tighter than loose”, so they deliberately increase the tightening torque, resulting in bolts slipping. In addition, for some important bolts that need to be tightened with torque, some people use adjustable wrenches to save trouble. As a result, insufficient torque causes the bolts to loosen and even causes mechanical failure.

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5. The washer is too large

Sometimes there is a lack of washers of the right size, and some workers use washers with larger inner diameters instead. In this case, the contact area under the bolt head with the washers is small, which will reduce the bearing pressure or locking force of the washers. If there is vibration and shock in the working environment, the bolts are easy to loosen.

6. Improper locking

The bolts should be locked with anti-loosening devices after the assembly is completed. Here are four cases to explain. If a split pin is used for locking, it must not be locked with a thin split lock or half-piece split lock; if a spring washer is used for locking, it must not be used with a washer that has too small an opening gap; if a lock plate is used for locking, the lock plate must not be locked in The edges and corners of the nut; if a double nut is used for locking, the thinner nut must not be installed outside.

7. False and solid

If the bolts, nuts or threads are rusted, or impurities such as scale, iron filings, etc. must be cleaned before assembly, and the joint surface of the coupling must be cleaned of impurities such as burrs, sand, etc. Otherwise, when the bolts are tightened, the surface looks Tightened, but in fact the coupling is not really compressed. Under such false solidity, the bolt will loosen quickly if vibration, load shock and temperature change occur.

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