How To Match The Grade Of Bolt And Nut?

Nut grade analysis:

Nuts are classified into ordinary, non-standard, (old) national standard, new national standard, American, British and German standards according to different national standard numbers corresponding to product properties. Hexagon nuts are divided into Type I, Type II and thin type according to the nominal thickness. Nuts above Grade 8 are divided into Type I and Type II.

Type I hexagon nuts are the most widely used. Type I nuts are divided into three grades: A, B and C. Among them, Grade A and B nuts are suitable for machines, equipment and structures with low surface roughness and high precision requirements, while Grade C nuts are used for machines, equipment or structures with rough surface and low precision requirements; The thickness of Type II hexagon nut is relatively thick, and it is often used in situations where assembly and disassembly are often required.

Common national standards for nuts:

GB41 Type I Hexagon Nut - Grade C

GB6170 Type I Hex Nut - Grade A and B

GB6171 Type I Hex Nut - Fine Thread - Grade A and B

GB6172 Hexagon thin nut - Grade A and B - chamfer

GB6173 Hexagon thin nut - fine thread - grade A and B

GB6174 Hexagon thin nut - Grade B - no chamfer

GB6175 Type II Hexagon Nut - Grade A and B

GB6176 Type II Hexagon Nut - Fine Thread - Grade A and B

GB6177 Hexagon Flange Nut - Grade A

GB55 Hexagon thick nut

GB56 hexagon super thick nut

GB1229 large hexagon nut (high strength for steel structure)

Metric bolt grade: 4.6; 4.8; 5.8; 6.8; 8.8; 9.8; 10.9; 12.9.

Metric nut grades are: 4; 5; 6; 8; 10; 12 of which 4; 5 is the strength grade of thin nut.

Nut A; B; Grade C is equivalent to American made G2; G5; The performance level of G8 is basically the same as that specified in J995!

The thread specification of I-type nut is M1.6~M64, and the performance grade is 6; 8; 10; A2-50; A2-70; A4-50; A4-70; CU2; CU3 and AL4, product grade A and B, grade A is used for specifications smaller than or equal to M16; Class B is used for specifications larger than M16! (A and B here refer to the accuracy grade);

The thread specification of type II nut is M5~M36, the performance grade is 9 and 12, the product grade is A and B, and the grade A is used for the specification less than or equal to M16; Class B is used for specifications larger than M16! (A and B here refer to the accuracy grade);

Due to the high performance level requirements of Type 2, the thick bolts with nuts have more than 10 performance levels, including 3.6, 4.6, 4.8, 5.6, 6.8, 8.8, 9.8, 10.9 and 12.9. The bolts of Grade 8.8 and above are made of low-carbon alloy steel or medium carbon steel and heat treated (quenched and backfired). They are generally referred to as high-strength bolts, and the rest are commonly referred to as ordinary bolts.

How do the grades of bolts and nuts match? If the bolt adopts grade 8.8, what grade should the nut adopt?

Metric bolt grade: 4.6; 4.8; 5.8; 6.8; 8.8; 9.8; 10.9; 12.9.

Metric nut grades are: 4; 5; 6; 8; 10; 12 of which 4; 5 is the strength grade of thin nut.

Then, is it meaningful to use 8.8 for bolts and 4 for nuts?

First of all: 8.8 and 4 are too unscientific.

Generally, the grade of nuts is determined by removing the decimal number behind the bolt grade. Grade 8.8 bolts are equipped with Grade 8 nuts, and Grade 10.9 bolts are equipped with Grade 10 nuts.

That is, the strength grades of bolts and nuts are the same (the strength grades of bolts 8.8 and nuts 8 are the same, because the ". 8" behind the bolts indicates that the yield strength is 80% of the tensile strength.)

However, considering the use, if the nut is not easy to replace, the bolt is easy to replace, which can also be changed to bolt 4.8 and nut 5.

In some cases, the strength of the nut is lower than that of the bolt. The main reason is that the failure of the bolt is usually undetectable, sometimes sudden, and the failure of the nut is easier to be found. Safety is also considered. In this way, the service life of the screw is longer than that of the nut when it is used together, and the cost of disassembling and replacing fasteners will be lower and easier.

For Jinrui, whether you are a fastener demander/dealer/supplier, you can visit the official website of Jinrui:http://www.jinruibolt.com/

Part of Jinrui's product display

      

Jiangsu Jinrui Metal Products Co., Ltd. is the production base of Shanghai Jinrui standard parts. The factory covers an area of more than 20000 square meters, with a registered capital of 50 million yuan, a total investment of more than 100 million yuan, and an annual output of more than 20000 tons. Its products are exported to more than 40 countries.

Since its establishment in 2001, Jinrui Company has developed into a new layout with Hai'an in Jiangsu as its production base and Baoshan in Shanghai and Nanyang in Henan as its sales centers after more than 20 years of unremitting efforts.

At present, Jinrui's main products include the following six categories:

1. The main products of bolts include metric and American round head oval neck bolts (also called fishtail bolts), internal and external hexagon bolts, hexagon flange bolts, carriage bolts, wheel hub bolts, etc

2. Stud products: full thread thread, double head studs, etc

3. Nut products: hexagon nut, flange nut, heavy nut, square nut, butterfly nut, etc

4. Screw products: self tapping screws, self tapping self drilling screws, wood screws, various machine screws, etc

5. Washer products: flat washer, spring washer, square washer, lock washer, etc

6. Fastener related non-standard products

The wire drawing plant under Jinrui Company also provides processing services such as fine drawing, rough drawing and spheroidizing of wire rods, and supplies finished wire rods of various domestic famous steel mills.

Adhering to the business philosophy of "pioneering and innovation, pursuing excellence", Jinrui has successively introduced multiple types of heading and forming machines, thread rolling machines, nut machines, hot heading and rolling machines, lathes, large hot heading machines and their supporting testing equipment, such as magnetic particle flaw detectors, metallographic analyzers, salt spray testing machines, direct reading spectrometers and optical screening machines, tensile machines, Vickers hardness meters, Rockwell hardness meters, etc., and has set up independent research and development departments, It can produce all kinds of high-quality fasteners such as GB, DIN, ANSI, JIS and ISO international standards. The products are widely used in petroleum, chemical industry, boiler, wind power generation, highway guardrail board, elevator guide rail, machinery manufacturing, construction sites, auto parts, medical equipment and other fields.

Jinrui has been developing vigorously since its establishment. It integrates the advantages of each company, carefully designs and strictly selects materials to make the products more durable, and is highly praised by the majority of users. Jinrui won the ISO9001: 2000 international quality system certification in 2001, the special equipment manufacturing license in 2010, and the TS16949 automobile quality management system certification in 2012. The People's Insurance Company of China underwrites the "Global Product Liability Insurance" for its products, ensuring that every screw can be used with confidence, determination, and peace of mind!

Whether now or in the future, Jinrui will always adhere to the core service concept of "quality first, science and technology to revitalize enterprises, users first, and considerate service", sincerely provide you with high-quality services and high-quality products, and Jinrui will also become your most loyal long-term partner.