Precautions for the use of standard parts
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- Time of issue:2021-07-21
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(Summary description)For important couplings on the machine, such as drive shafts, flyshafts, etc., the bolts mostly use fine thread. When parts are missing in the repair, someone replaces them with coarse-threaded bolts. Because of the larger inner diameter, smaller pitch and outer angle, the fine pitch bolt has the advantages of high strength, good self-locking performance, etc., and strong ability to withstand impact, vibration and exchange load; it is easy to loosen or fall off and break after being replaced by coarse-threaded bolts. , Causing a mechanical accident.
Precautions for the use of standard parts
(Summary description)For important couplings on the machine, such as drive shafts, flyshafts, etc., the bolts mostly use fine thread. When parts are missing in the repair, someone replaces them with coarse-threaded bolts. Because of the larger inner diameter, smaller pitch and outer angle, the fine pitch bolt has the advantages of high strength, good self-locking performance, etc., and strong ability to withstand impact, vibration and exchange load; it is easy to loosen or fall off and break after being replaced by coarse-threaded bolts. , Causing a mechanical accident.
- Categories:Industry News
- Author:
- Origin:
- Time of issue:2021-07-21
- Views:0
Precautions for the use of standard parts
Common misunderstandings in the use of standard parts:
01 Substitute coarser for finer
For important couplings on the machine, such as drive shafts, flyshafts, etc., the bolts mostly use fine thread. When parts are missing in the repair, someone replaces them with coarse-threaded bolts. Because of the larger inner diameter, smaller pitch and outer angle, the fine pitch bolt has the advantages of high strength, good self-locking performance, etc., and strong ability to withstand impact, vibration and exchange load; it is easy to loosen or fall off and break after being replaced by coarse-threaded bolts. , Causing a mechanical accident.
02 Pore does not match
The bolts (such as drive shaft bolts, flywheel bolts) on the machine that bear the lateral load and shearing force, their fit with the bolt holes are transitional fits, and the assembly should be strong and reliable, and can withstand lateral forces. Someone did not pay attention to the inspection during the assembly, and the bolt was still installed when there was a large gap between the bolt and the bolt hole. As a result, the bolt was loose or cut off.
03 Thick nut
Some people often mistakenly believe that thickening the nut can increase the number of working turns of the thread, thereby improving the reliability of the coupling. In fact, the thicker the nut, the more uneven the load distribution between the threads of each circle, and the easier it is to loosen the coupling.
04 One female with multiple pads
During installation, sometimes the bolts after assembly are too long, so someone installs many spring washers on a bolt. In this way, the spring washers are not evenly stressed during the tightening process, and some will break, which will pre-tighten the bolts. The force drops; or eccentric load is generated, which reduces the reliability of the bolt connection.
05 Washer is too large
Sometimes, due to the lack of suitable gaskets, some people use gaskets with larger inner diameters instead. In this way, the contact area under the head of the bolt with the washer is small, the bearing pressure or locking force of the washer is reduced, and the bolt is easy to loosen under the action of vibration and impact load.
06 Torque does not match
Many people think that bolts should be “tighter than loose”, so they consciously increase the tightening torque of the bolts, which results in the bolts slipping. On the other hand, for important bolts that need to be tightened with torque, some people try to save trouble by using adjustable wrenches. Unscrew, the result is often loose due to insufficient torque, leading to mechanical failure.
07 Improper locking
Important bolts should be locked with anti-loosening device after assembly. When using a split pin to lock, the common mistake is to use a thin split lock or a half-piece split lock to lock; when using a spring washer to lock, the common mistake is that the gap of the washer opening is too small and loses elasticity; using a lock plate to lock Yes, the common mistake is to lock the lock plate at the corners of the nut; the double nut is used to lock, the common mistake is to install the thinner nut on the outside and not tighten it tightly.
08 sturdy
There are impurities such as rust, scale, iron filings, sand particles in the threads of bolts, nuts or screw holes, or there are impurities such as burrs and sand on the joint surface of the coupling parts, which have not been removed before assembly. When tightening the bolts, due to impurities Blocking effect, the surface is tightened very tightly, the torque value meets the requirements, but in fact the coupling is not really compressed; in addition, there is another situation, due to the supporting effect of impurities such as sludge and scale in the screw hole, Although the bolt torque complies with the regulations, the work piece is not compressed. Under such sturdiness, vibration, load shock and temperature changes often cause the bolts to loosen quickly.
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