There are 4 types of hex nuts commonly used:
1. GB/T 41-2016 "Type 1 Hex Nut Grade C"
2. GB/T 6170-2015 "Type 1 Hex Nut"
3. GB/T 6175-2016 "Type 2 Hex Nuts"
4. GB/T 6172.1-2016 "Hexagon Thin Nut"
The main differences between the four commonly used nuts are as follows:
1. Nut heights are different:
According to the provisions of the national standard GB/T 3098.2-2015 "Mechanical Properties of Fasteners Nuts", there are three types of nut heights:
——Type 2, high nut: minimum height min≈0.9D or >0.9D;
——Type 1, standard nut: minimum height min≈0.8D;
——Type 0, thin nut: minimum height 0.45D≤mmin<0.8D.
Note: D is the nominal diameter of the nut thread.
Among the above four commonly used nuts:
GB/T 41-2016 "Type 1 Hex Nut Grade C" and GB/T 6170-2015 "Type 1 Hex Nut" are Type 1 standard nuts, and the minimum height of the nut is min≈0.8D.
GB/T 6175-2016 "Type 2 Hex Nuts" is a type 2 high nut, and the minimum height of the nut is mmin≥0.9D.
GB/T 6172.1-2016 "Hexagon Thin Nut" is a type 0 thin nut, and the minimum height of the nut is 0.45D≤mmin＜0.8D.
2. Different product grades:
The product grades of nuts are divided into A, B, and C grades. The product grades are determined by the tolerance size. A grade is the most accurate and a C grade is the least accurate.
GB/T 41-2016 "Type 1 Hexagon Nuts Grade C" specifies nuts with grade C precision.
GB/T 6170-2015 "Type 1 Hexagonal Nuts", GB/T 6175-2016 "Type 2 Hexagonal Nuts" and GB/T 6172.1-2016 "Hexagonal Thin Nuts" stipulate the nuts with grade A and grade B precision.
In GB/T 6170-2015 "Type 1 Hexagonal Nuts", GB/T 6175-2016 "Type 2 Hexagonal Nuts" and GB/T 6172.1-2016 "Hexagonal Thin Nuts", Grade A is used for nuts with D≤16mm; Grade B is used for nuts with D>16mm.
According to the national standard GB/T 3103.1-2002 "Fastener Tolerance Bolts, Screws, Studs and Nuts", the internal thread tolerance grade of A-level and B-level precision nuts is "6H"; The tolerance grade of the internal thread is "7H"; the tolerance grades of other dimensions of nuts are different according to the accuracy of grades A, B and C.
3. Different grades of mechanical properties
According to the provisions of the national standard GB/T 3098.2-2015 "Mechanical Properties of Fastener Nuts", bolts made of carbon steel and alloy steel have 7 types of mechanical performance grades under the condition of an environmental dimension of 10°C to 35°C. They are 04, 05, 5, 6, 8, 10, and 12 respectively.
According to the provisions of the national standard GB/T 3098.15-2014 "Mechanical Properties of Fasteners Stainless Steel Nuts", when the environmental dimension is 10°C to 35°C, the performance grades of nuts made of stainless steel are specified as follows:
Nuts made of austenitic stainless steel (including A1, A2, A3, A4, and A5 groups) have mechanical properties of 50, 70, 80, 025, 035, and 040. (Note: The mechanical performance grade of stainless steel nuts is composed of two parts, the first part marks the steel group, and the second part marks the performance grade, separated by dashes, such as A2-70, the same below)
Nuts made of martensitic stainless steel of group C1 have mechanical property grades of 50, 70, 110 and 025, 035, 055;
Nuts made of martensitic stainless steel of group C3 have mechanical properties of 80 and 040;
Nuts made of martensitic stainless steel of group C4 have mechanical property grades of 50, 70, and 025, 035.
Nuts made of F1 group ferritic stainless steel have mechanical property grades of 45, 60, and 020, 030.
According to the provisions of the national standard GB/T 3098.10-1993 "Mechanical Properties of Fasteners - Bolts, Screws, Studs, and Nuts Made of Non-ferrous Metals":
Nuts made of copper and copper alloys have mechanical performance grades: CU1, CU2, CU3, CU4, CU5, CU6, and CU7;
Nuts made of aluminum and aluminum alloys have mechanical performance grades: AL1, AL2, AL3, AL4, AL5, and AL6.
The national standard GB/T 41-2016 "Type 1 Hexagon Nut Grade C" is applicable to grade C hexagon nuts with thread specifications M5 ~ M64 and performance grade 5.
The national standard GB/T 6170-2015 "Type 1 Hexagon Nut" is applicable to thread specifications M1.6~M64, performance grades are 6, 8, 10, A2-70, A4-70, A2-50, A4-50, CU2, CU3, and AL4 grade A and B hex nuts.
The national standard GB/T 6175-2016 "Type 2 Hexagon Nuts" is applicable to grade A and grade B hexagon head bolts with thread specifications M5~M36 and performance grades 10 and 12.
The national standard GB/T 6172.1-2016 "Hexagon Thin Nut" is applicable to thread specifications M1.6~M64, performance grades are 04, 05, A2-025, A2-035, A2-50, A4-035, CU2, CU3 and AL4 grade A and B hexagonal thin nuts.
Standard nuts (type 1) and high nuts (type 2) made of carbon steel and alloy steel should be used with externally threaded fasteners in the following table, and nuts with higher performance energy levels can replace nuts with lower performance grades.
Standard nuts (Type 1) are very widely used.
Tall nuts (type 2) are generally used in connections that require frequent disassembly.
Thin nuts (Type 0) have lower load-carrying capacity than standard or tall nuts, so they should not be designed for anti-tripping applications.
Thin nuts (type 0) are generally used in double-nut anti-loosening structures.
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