What are the grades of screws and bolts?
Steel structure connecting bolts 3.6, 4.6, performance grade 4.8, 5.6, 6.8, 8.8, 9.8, 10.9, 12.9 and more than 10 levels, of which 8.8 or more bolt material for low carbon alloy steel or carbon steel by heat treatment (quenching and tempering), known as the high strength bolts, known as the rest ordinary bolt. There are two parts in the performance grade of bolts. They are the nominal tensile strength of the bolt material and the ratio of the tensile strength. Such as:
A bolt with a performance rating of 4.6:
1. Nominal tensile strength of bolt material reaches 400MPa grade;
2, the bolt strength ratio is 0.6;
3. The nominal yield strength of bolt material is 400 * 0.6=240MPa class
Performance class 10.9 high strength bolt whose material can be reached after heat treatment:
1. Nominal tensile strength of bolt material reaches 1000MPa grade;
2, the bolt strength ratio is 0.9;
3. The nominal yield strength of bolt material is 1000 * 0.9=900MPa class
The meaning of the performance grade of a bolt is an international standard. The performance of the bolt of the same performance grade is the same regardless of the material and the place of origin. The performance grade can only be used in the design.
The strength grades, grade 8.8 and grade 10.9, refer to the shear stress levels of the bolts 8.8GPa and 10.9GPa
8.8 nominal tensile strength 800N/MM2 nominal yield strength 640N/MM2
The ordinary bolt is expressed with the strength of "X.Y", the tensile strength of the bolt X*100=, X*100* (Y/10) = the yield strength of the bolt (as specified by the mark: yield strength / tensile strength =Y/10)
Class 4.8
The tensile strength of the bolt is 400MPa, and the yield strength is 400*8/10=320MPa.
Another: stainless steel bolts are usually labeled "A4-70", "A2-70" look, meaning otherwise explained
There are two main measures: one of the world's length measuring unit, a metric unit of measure for the meter (m), cm (CM), mm (mm), is widely used in Europe, China and Japan in Southeast Asia, the other one is British, mainly for inch units of measurement (inch) in China, the equivalent of the old rural, is widely used in the United States, Britain and other European countries.
1, metric measurement: (10 hexadecimal), 1M, =100, cm=1000, mm
2 inch (8 m) measurement: 1 inch =8 1 inch =25.4 mm British 3/8's =9.52 * 25.4
3, 1/4's following products used to represent the size designation name, such as: 4#, 5#, 6#, 7#, 8#, 10#, 12#
Thread
A thread is a solid outer surface or inner surface of the cross section, there is a uniform spiral line convex shape. According to its structure, characteristics and uses can be divided into three categories:
(1) ordinary threads: the teeth are triangular in shape and are used for connecting or fastening parts. The ordinary thread is divided into two kinds of coarse and fine thread according to the pitch, and the connection strength of the fine thread is higher.
(two) driving thread: tooth shape has ladder, rectangle, saw shape and triangle etc..
(three) sealing threads: used for sealing connections, mainly for threads, taper threads and taper pipe threads.
Two, thread matching level:
The thread matching is the loose or tight size between the screw threads, and the grade of fit is the combination of the deviation and the tolerance on the inside and outside threads.
(1) to the unified English thread, there are three kinds of thread grades: 1A, 2A and 3A. There are three grades of internal thread: 1B, 2B and 3B, all of which are clearance fit. The higher the grade, the tighter the tie. In British threads, deviations are only specified for grades 1A and 2A, deviations from class 3A are zero, and class deviations for 1A and 2A are equal. The larger the grade, the less the tolerance.
1, 1A and 1B class, very loose tolerance level, which is suitable for internal and external thread tolerance match.
2, 2A and 2B class, is the British family of mechanical fasteners, the most common thread tolerance class.
3, 3A and 3B grade, spin forming the most tight fit, suitable for tight fasteners, for security critical design.
4, the external thread, 1A and 2A class has a matching tolerance, 3A class no.. The 1A tolerance is 50% larger than the 2A tolerance, 75% larger than the 3A grade, and the 2B tolerance is 30% greater than the 2A tolerance for internal threads. 1B is 50% larger than 2B, 75% larger than 3B.
(two) metric thread, the external thread has three kinds of thread grades: 4h, 6h and 6G, the internal thread has three kinds of thread grades: 5H, 6, H, 7H. (Japan standard thread accuracy grade is divided into I, II and III three, usually under the II class) in metric thread, the basic deviation of H and H is zero. The basic deviation of G is positive, and the basic deviation of E, F and G is negative. As shown:
1 and H are common tolerances for internal threads. They are generally not used as surface coating or with extremely thin phosphating layers. The basic deviation of G position is used for special occasions, such as thicker coating, which is seldom used.
2 and G are often used for 6-9um plating of thin coating, such as product drawings require 6h bolt, its plating thread before using 6G tolerance zone.
3, screw with the best combination of H/g, H/h or G/h, for bolts, nuts and other refined fasteners thread, the standard recommended by the use of 6H/6g coordination
(three) thread mark
Four 、 the main geometric parameters of self drilling and self drilling thread:
(1) big diameter / tooth outer diameter (D1), the diameter of the imaginary cylinder that coincides with the top of the thread. The big diameter of screw thread basically represents the nominal diameter of thread size.
(two) path / tooth bottom diameter (D2): the imaginary cylinder diameter of the bottom of the screw thread.
(three) the distance between teeth (P): the axial distance between adjacent teeth on the middle meridian corresponds to the two points. In English, the number of teeth per inch (25.4mm) indicates the pitch of the teeth.
The following table lists the tooth distance (Metric) teeth (English) of the commonly used specifications
1, metric self tapping teeth:
Specifications: S, T 1.5, S, T1.9, S, S, T2.6, S, T2.9, S, T3.3, S, S, T3.9, S, T4.2, S, T4.8, S, T2.2, T5.5, S, T3.5, T6.3, S,, T8.0, S, T9.5
Tooth distance: 0.5, 0.6, 0.8, 0.9, 1.3, 1.3, 1.1, 1.3, 1.4, 1.6,, 1.8, 1.8, 2.1, and 2.1
2, British self tapping teeth:
Specifications: 4#, 5#, 6#, 7#, 8#, 10#, 12#, 14#
Number of teeth: AB teeth 24, 20, 20, 19, 18, 16, 14, and 14
A teeth 24, 20, 18, 16, 15, 12,, 11 and 10
