If you look at a car, look at the screws.
Let's start by popularizing fasteners. Screws are a kind of fasteners, I do mainly screws. Screws are broadly called, subdivided into screws (such as self-tapping nails, fiberboard nails, etc.) and bolts. Screws are divided into standard and non-standard parts according to standards, standard parts are produced according to various standards, such as the national standard, German standard, Japanese standard, American standard, etc., non-standard parts are customized according to customer requirements. Bolt size generally have two classifications, such as our common M6, M8, M10, etc. is the national standard called, 1∕4, 3∕8, 1∕2 is the British system called, the national standard called the size of our good understanding, then the British system? We can convert, as long as multiplied by 25.4 can be, such as 1∕4, 1∕4 * 25.4 is equal to the size of M6.
Bolt grade common 4.8 ∕ 8.8 ∕ 9.8 ∕ 10.9 ∕ 12.9 (GB), the higher the grade, the higher the hardness of the bolt, we look at the head of the bolt, there will be marked, if you are Japan and South Korea, it is the head of the general standard will be 7T ∕ 8T ∕ 10T, roughly equivalent to the 8.8 ∕ 10.9 grade, 4.8 grade screws do not need to go through the heat treatment, so it's softer! 4.8 grade screws do not need to be heat-treated, so it is softer, 4.8 grade and above need to be heat-treated.
Automotive screws are high-end fasteners in the project, is different from the ordinary screws, you may wonder, not just screws, and how high? In fact, not, car screws are mostly non-standard parts, from design to development, to production are different from ordinary screws. So I advise you, the car screws need to be replaced, do not catch a similar screws to load, which is by the security risks, even if it is a temporary emergency, we must also see the head label, do not use different levels of screws, which is the most minimal requirements. Screws seem to be very common, but in fact it does have a lot to learn, two screws of the same size, the slightest change in the nuances, then it is a big difference in mechanical properties, and these differences are often not by the naked eye to see. For example, a screw, its head and rod connection, there will be a very small arc, we call it R angle, this R angle in the design and production will have strict requirements, if too big or too small will have problems, after carrying a certain amount of force is likely to fracture, or even drop head!