How many teeth are exposed in a bolt-nut connection?
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Recently, I encountered a design from headquarters where the bolts and nuts are flush after being tightened. Based on my previous experience, it’s usually necessary to leave 1–3 threads exposed. I would like to ask this knowledgeable forum: is there any change in standards or regulations that has led to this change? Thank you!
I found a relevant regulation: GB50235—2010 7.3.4 Flange connections shall use bolts of the same specification, and the installation direction shall be consistent. The bolts should be tightened symmetrically. Bolt tightening
GB50235—2010 7.3.4 Flange connections shall use bolts of the same specification, and the installation direction shall be consistent. The bolts should be tightened symmetrically. After bolt tightening, it should be in close contact with the flange, with no wedging gap. When washers need to be added, no more than one should be used per bolt. All nuts should be screwed onto the bolts, and the bolts and nuts after tightening should be at the same level.
In our country, it is generally required that the bolt protrude 2 to 3 threads above the nut, but most foreign standards require that the bolt and nut be tightened so that they are level with each other.
This post was last edited by Forgetting = Forgetting on 2019-8-22 at 13:48. Generally, 2-3 threads of the bolt head are exposed, and this will not change. 1. The part that extends beyond the nut is not subject to tightening forces; the bolt is kept short, which facilitates installation and maintenance. 2. The threads at the chamfered end of the bolt are subjected to relatively low stress, about 1 tooth per 3. Due to the difference between the theoretical and actual gasket compression ratios, bolts are usually chosen to be slightly longer; for those who are not very familiar with this process, the bolts generally protrude by about 1 centimeter
GB50235-2010 Code for Construction of Industrial Metal Piping Projects (Bolt Tightening 7.3.4) and Interpretations
Under normal circumstances, it’s 2 to 3 deductions; of course, as someone mentioned earlier, it’s also correct to follow the requirements specified in \"GB50235-2010 Code for Construction of Industrial Metal Piping Projects (Section 7.3.4 on bolt tightening) and its interpretations\"
These days, it is generally better for the bolt and nut to be at the same level after tightening
There are often conflicts in the regulations in our country; however, from level to 3 threads, there is evidence to support it, but it must not be insufficient.