First of all, because the contact area between the straight and cross openings and the tool is not at the same level as the contact area between the inner and outer hexagons and the tool, there is almost no problem of twisting the inner and outer hexagons (but there are also screwed inner hexagons into round holes.
Furthermore, the screw-tightening tool must be suitable, it must be suitable (if you want to install it again, it will not be discussed at one time), everyone will easily find an unsuitable tool to screw the slotted and Phillips screws There are many situations (take a big, thick screwdriver to unscrew the small nails on the back of the laptop), but it is difficult to find an inappropriate tool for internal and external hexagons.
Next, the slotted and cross screws are not for you to twist hard, you just need to tighten them with appropriate force. Unfortunately, the person who will unscrew them later is not as strong and skilled as you, and there is a great risk of screwing them up. .
Finally, the slot is going to be spent or has already been spent. Please replace it with a new one after unscrewing it... At the same time, if it is rusty, please solve the rust problem first, and then unscrew it after removing the rust.
Emphasis, be a moral person, don't put back the screws that are almost spent! When I encounter a screw that has been spent in a bad shape, I wish I could find the person who touched it before.
For those who are engaged in mechanics, don't look at it. "If you want to learn mechanics well, you must draw the bolts skillfully." How many students who learn mechanics first fold on the bolts...After folding the bolts, they are checked bolt. The basic skills of drawing must be solid, so that you can complain about other people's pictures in the future. There are very few pictures that are drawn by one person without any mistakes. Learning drawing well can be "both offensive and defensive".
If you are only talking about the "screws" in the standard parts, rather than the wider "threaded connections" or "threaded fasteners", the common "screws" also have the words cross and one, and there is an inner Hexagonal (rare in household appliances, but can be seen in cars, bicycles, etc.). Of course, the non-standard parts are unconstrained, just to prevent you from disassembling them easily, so they must be different.
Let me talk about why there are at least three types: one character, cross, and inner hexagon.
In fact, one word is used less and less, and there will be more carpenters, because it does not have much advantage over the cross, and the processing cost that was once considered is no longer different. Easy to find replacements. Now these are not big problems, many places, or almost all occasions can be replaced by crosses. The advantage of the cross is that it is not easy to twist (tools must be suitable, not easy to twist too small or vice versa), and the inner hexagonal wrench is easier to tighten, because the inner hexagonal wrench usually looks like this:
To expand a little bit, what the subject may want to ask is: Why are there "joints" that are round, cylindrical and conical?
In fact, it mainly depends on the application occasion. The last two are countersunk head screws, which are used where countersunk heads are required. If you don’t understand, turn the laptop over and see that they are all countersunk heads. Why do you think for yourself. Then why not use the countersunk head? Because the countersunk head needs to be processed more (in fact, not necessarily, the "special" tool can fix the countersunk head and hole at once), and it saves money and trouble in occasions where it is not necessary. Especially for the cone, due to the self-centering feature of the cone, it can ensure that the two connected holes are concentric (see the difference between the third picture and the fourth picture, the cylindrical counterbore and the screw have a gap, and the conical one No).
In fact, mechanically, "threaded parts" are usually classified according to the thread, because the thread is the place where the characteristics are determined.
For the masses, what is the easy-to-understand classification of threaded connectors?
The first classification (with or without nuts): screws, bolts
The second classification (convex or not): countersunk head, non-sunk head
The third classification: cross, one character, inner hexagon, outer hexagon, special shape
I feel that this is enough, and other classifications are not popular.
Then please arrange and combine them yourself: for example, hexagon socket head bolts, cross countersunk screws, etc., almost theoretically possible, but some are not common.
Screws and bolts.
1. Screws and bolts
The main difference between a screw and a bolt is that the screw works alone, and the thread that matches the screw is processed on the workpiece; the bolt and the nut work together, and the thread that cooperates with the bolt is processed on the nut. They have similar functions, but they are used in different occasions. Bolts and nuts are pre-purchased standard parts, and the objects to be connected only need to punch a suitable through hole, which is simple and low in cost; screws are used when bolts cannot be used. For example, one of the objects to be linked is too thick (or for other reasons) to be drilled through the hole, so we have to process threaded holes on it and link them with screws, which increases the cost (the threaded hole needs one more step of tapping than the light hole).
2. Allen screws, bolts and Allen wrench
1. Hexagon socket screws are easy to see, and many bicycles are used, see the picture
picture
This product needs to be screwed with the following thing (there are also electric tools, and I will add it at the end)
picture
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The size must be correct. There are national standards. Generally, it will not be a special size. There must be suitable tools.
Outer hexagonal bolts, just say bolts, the default bolts are outer hexagonal bolts, also known as hexagonal bolts
Generally, it is more convenient to screw with a sleeve, and it can be repaired both internally and externally (it can be screwed with or without a sinking head, and it is more convenient)
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If the bolts are not countersunk and there is enough space for the wrench, you can also use a wrench, which is less efficient, but the wrench is versatile (the applicable diameter range is large), and the wrench has been seen
