What is the appropriate length of the screw connection? This seems like a simple question, but there are many situations.
Let’s first take a look at the relevant provisions of the standards in the manual
The table above gives the remaining length of the internal and external threads of common threads, the remaining drilling depth and the end length of the bolt protruding beyond the nut.
If the depth of the threaded hole is designed (referring to the depth of the threaded part), the depth of our threaded hole is generally 1.5-2 times the diameter of the thread.
For example, how deep is the M10 screw hole? It can be designed based on 15-20mm depth, of course, it depends if your space is enough. If the thickness of the workpiece is relatively thick, the depth can be 20mm. If it is not very thick, the depth can be reduced appropriately.
The advantage of being deeper is that the screws have greater adaptability. For example, if the thread is only 10mm deep, the screw may only be available in one length. If it is 20mm deep, two or three lengths of screws can be used. It is simply a technique summarized in an actual assembly and is not necessarily rigorous.
If it is a combination of screws and nuts, it is recommended that the screws protrude at least 2-3 teeth from the nut, which is usually 3-4mm. Note that what is said here is at least, that is, try to make the nut protrude a certain distance after assembling the screw, so that it fits better!
Does material affect thread depth requirements? The answer is yes. Try to think about it. If soft material is used for only 3 teeth, will the teeth slide easily? In fact, the softer the material, the greater the thread depth should be. Different materials require different screw lengths.
For example, for steel, the threaded length of the M3 bolt is designed to be 4mm; if it is gray cast iron, the threaded length of the M3 bolt is designed to be 6mm; the M3 bolt is designed to measure 8mm. Of course, I personally think that if there is enough space, we can design the thread length of the M3 bolt to 8mm, so that it is easy to remember.
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