1, what is the ultra-short bolt Ultra-short bolt is a very high resistance bolt, can resist acid, alkali salt corrosion. And the basic composition is different, it shows the resistance of the car focus is also different, so there is also rust resistance, but it can not resist acid. In our daily life, the ultra-short bolts used are derived from austenitic stainless steel, which is divided into austenitic 304, 316 and other models.
2, strength grade ① The performance grade of the common ultra-short bolt is 8.8, which refers to the tensile strength of 800MPa and the yield strength of 640MPa. Ultra short bolts from bolt to stud can be divided into 10 grades in performance, from 3.6 to 12.9. This decimal point does not represent a mathematical decimal point, the left of the decimal point represents the strength limit of the material, and the right of the decimal point represents the ratio of the yield limit to the tensile limit. ② The nut also has seven grades, from 4 to 12, and the larger the number, the minimum stress that the nut can withstand. ③ According to the bolt pattern, the external thread can be divided into 1A, 2A and 3A, and the internal thread is divided into :1B, 2B and 3B. The larger the number, the higher the level, the tighter the fit. 1A, 1B: The tightness needs to be improved, only applicable to the tolerance of internal and external threads. 2A, 2B: Adopts the inch series firmware, the most commonly used thread tolerance level. 3A, 3B: This grade is the tightest and is mainly used in some safety-critical designs. ④ Thread grade, there are external threads and internal threads. External thread :4H, 6H and 6G; Internal threads are divided into :5H, 6H and 7H. The fit of the thread is also best h/g, h/h or g/h, and the bolts of this combination are strong.
3, the type of ultra-short bolts there are very many types of ultra-short bolts, even dozens of points, and different specifications, their purposes are different. For example: outer hex bolts, hex tip set screws, half round head hex screws, cross slot large flat head self-tapping nails, hex nuts, butterfly nuts and so on.
