The difference and selection of commonly used hexagon bolts
There are 4 commonly used hexagon bolts:
1. GB/T 5780-2016 "Hexagon Head Bolts Class C"
2. GB/T 5781-2016 "Hexagon head bolts with full thread C grade"
3. GB/T 5782-2016 "Hexagon Head Bolts"
4. GB/T 5783-2016 "Hexagon head bolts with full thread"
The main differences between the four most commonly used bolts are as follows:
1. Different thread lengths:
The thread length of the bolt is full thread and non-full thread.
Among the above 4 commonly used bolts
GB/T 5780-2016 "Hexagon Head Bolts Class C" and GB/T 5782-2016 "Hexagon Head Bolts" are non-full threaded bolts.
GB/T 5781-2016 "Hexagon Head Bolts Full Thread Class C" and GB/T 5783-2016 "Hexagon Head Bolts Full Thread" are full threaded bolts.
GB/T 5781-2016 "Hexagon Head Bolts Full Thread Grade C" is the same as GB/T 5780-2016 "Hexagon Head Bolts Grade C" except that the product is made of full thread.
GB/T 5783-2016 "Hexagon head bolts with full thread" is the same as GB/T 5782-2016 "Hexagon head bolts" except that the product is made of full thread and the nominal length of the preferred length specification is up to 200mm.
Therefore, in the following analysis, it is only necessary to discuss the difference between GB/T 5780-2016 "Hexagon Head Bolts Class C" and GB/T 5782-2016 "Hexagon Head Bolts".
2. Different product grades:
The product grades of bolts are divided into A, B and C grades. The product grade is determined by the tolerance size. A grade is the most accurate, and C grade is the least accurate.
GB/T 5780-2016 "Hexagon head bolts C grade" stipulates the C grade precision bolts.
GB/T 5782-2016 "Hexagon head bolts" stipulates the bolts with grade A and grade B precision.
In the GB/T 5782-2016 "Hexagon Head Bolts" standard, Grade A is used for bolts with d=1.6mm～24mm and l≤10d or l≤150mm (according to the smaller value); Grade B is used for bolts with d>24mm or Bolts with l>10d or l>150mm (whichever is smaller).
According to the national standard GB/T 3103.1-2002 "Tolerance Bolts, Screws, Studs and Nuts for Fasteners", the external thread tolerance grade of bolts with grade A and B precision is "6g"; The tolerance level of external thread is "8g"; other dimensional tolerance levels of bolts vary according to the accuracy of A, B, and C grades.
3. Different mechanical properties:
According to the provisions of the national standard GB/T 3098.1-2010 "Mechanical Properties of Fasteners Bolts, Screws and Studs", the mechanical properties of bolts made of carbon steel and alloy steel under the condition of environmental dimension of 10 ℃ ~ 35 ℃ There are 10 levels, 4.6, 4.8, 5.6, 5.8, 6.8, 8.8, 9.8, 10.9, 12.9, 12.9.
According to the provisions of the national standard GB/T 3098.6-2014 "Mechanical Properties of Fasteners - Stainless Steel Bolts, Screws and Studs", under the condition of environmental dimension of 10℃～35℃, the performance grades of bolts made of stainless steel are as follows:
Bolts made of austenitic stainless steels (including A1, A2, A3, A4, A5 groups) have mechanical property classes 50, 70, 80. (Note: The mechanical property grade marking of stainless steel bolts consists 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)
Bolts made of C1 group martensitic stainless steel have mechanical property grades of 50, 70, and 110;
Bolts made of C3 group martensitic stainless steel have a mechanical property class of 80;
Bolts made of C4 group martensitic stainless steel have mechanical property grades of 50 and 70.
Bolts made of F1 martensitic stainless steels have mechanical properties grades 45 and 60.
According to the national standard GB/T 3098.10-1993 "Mechanical properties of fasteners - Bolts, screws, studs and nuts made of non-ferrous metals":
The mechanical properties of bolts made of copper and copper alloys are: CU1, CU2, CU3, CU4, CU5, CU6, CU7;
The mechanical properties of bolts made of aluminum and aluminum alloys are: AL1, AL2, AL3, AL4, AL5, AL6.
The national standard GB/T 5780-2016 "Class C Hexagon Head Bolts" is suitable for C grade hexagon head bolts with thread specifications M5 to M64 and performance grades 4.6 and 4.8.
The national standard GB/T 5782-2016 "Hexagon head bolts" is suitable for thread specifications M1.6～M64, and the performance grades are 5.6, 8.8, 9.8, 10.9, A2-70, A4-70, A2-50, A4-50, Grade A and B hex head bolts for CU2, CU3 and AL4.
The above is the main difference between these 4 commonly used bolts.
In practical applications, full-threaded bolts can be used instead of non-full-threaded bolts, and high-performance grade bolts can be used instead of low-performance grade bolts.
However, full-threaded bolts of the same specification are more expensive than non-full-threaded bolts, and high-performance grades are more expensive than low-performance grades.
Therefore, in normal occasions, bolts should be selected according to actual needs, and only in special occasions should "replace all faults" or "replace highs with lows".
