Precautions for Purchase and Use of Expansion Bolts
June 21,2022
Expansion bolt is a kind of fastener screw that uses wedge-shaped slope to promote the expansion of metal pipe to produce friction grip force, so as to achieve the fixed effect. Expansion bolts are widely used from construction sites to daily homes. For example, expansion bolts are required for fixing water heaters and water pipes.
How to choose suitable expansion bolts?
Confirm the size and weight of the object to be fixed, calculate the bearing load, and determine the diameter and length of the selected bolt.
According to the use environment, such as indoor, outdoor, or special environment, evaluate the selection of materials, such as stainless steel.
What should be paid attention to when using expansion bolts?
- drilling depth: the relevant information describes the length of the expansion pipe, but I found that this depth is not enough in the specific construction, which may be related to the residual amount of sundries in the hole, so you * * are still about 5mm deeper than the length of the expansion pipe. As long as you are greater than or equal to the length of the expansion pipe, the length of the expansion bolt left underground is equal to or less than the length of the expansion pipe.
- the requirement of expansion bolts on the ground is, of course, the harder the better, which also depends on the stress of the objects you need to fix. The stress strength installed in concrete (c13-15) is five times that in brick.
- after an m6/8/10/12 expansion bolt is correctly installed in the concrete, its not ideal static force is 120/170/320/510kg respectively.
In addition, the fixing of expansion bolts is not very reliable. Therefore, if the load has a large vibration, it may become loose. Therefore, it is not recommended to use expansion bolts when installing vibrating objects such as ceiling fans.
How to identify the strength grade of bolts and what is the difference between the grades?
The strength grade of bolts refers to the performance grade of bolts used for steel structure connection. There are more than 10 grades, such as grade 4.8, 8.8, 10.9 and 12.9. Bolts above grade 8.8 (including grade 8.8) are made of low-carbon alloy steel or medium carbon steel and heat treated (quenched and tempered), which are collectively referred to as high-strength bolts, and the rest are collectively referred to as ordinary bolts.
The bolt performance grade is composed of two numbers, which respectively represent the nominal tensile strength value and yield strength ratio of the bolt material. For example, a bolt with a performance grade of 4.8 means that the nominal tensile strength of the bolt material reaches 400MPa, and the yield strength ratio of the bolt material is 0.6; Nominal yield strength of bolt material up to 400 × 0.8=320mpa grade. By analogy, the nominal yield strength of grade 12.9 bolt material is 1200x0.9=1080mpa. The meaning of bolt performance grade is an international standard. Bolts with the same performance grade have the same performance regardless of their materials and origin. Only the performance grade can be selected in the design.
In life, we can often see some bolts with words like 4.8\8.8\12.9 on them. In fact, these are the marks of bolt strength grade, and sometimes we mistakenly think it is the size of the bolt.
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