M2 standard 0.40 fine thread 0.25
M2.5 standard 0.45 fine thread 0.35
M2.6 standard 0.45 fine thread 0.35
M3 standard 0.50 fine thread 0.35
M3.5 standard 0.60 fine thread 0.35
M4 standard 0.70 fine thread 0.50
M5 Standard 0.80 Fine Thread 0.50
M6 standard 1.00 fine thread 0.75
M8 standard 1.25 fine thread 1 1.00 fine thread 2 0.75
M10 standard 1.50 fine thread 1 1.25 fine thread 2 1.00 fine thread 3 0.75
M12 standard 1.75 fine thread 1 1.50 fine thread 2 1.25 fine thread 3 1.00
M14 standard 2.00 fine thread 1 1.50 fine thread 2 1.00
M16 standard 2.00 fine thread 1 1.50 fine thread 2 1.00
M18 standard 2.50 fine thread 1 2.00 fine thread 2 1.50 fine thread 3 1.00
The performance grades of bolts for steel structure connection are divided into more than 10 grades such as 3.6, 4.6, 4.8, 5.6, 6.8, 8.8, 9.8, 10.9, 12.9, among which the bolts of grade 8.8 and above are made of low-carbon alloy steel or medium-carbon steel and have been heat-treated (quenching, tempering), commonly known as high-strength bolts, and the rest are commonly referred to as ordinary bolts.
The bolt performance grade label consists of two parts of numbers, which respectively represent the nominal tensile strength value and yield strength ratio of the bolt material. For example: bolts with performance grade 4.6, its meaning is:
1. The nominal tensile strength of the bolt material reaches 400MPa; 2. The yield ratio of the bolt material is 0.6;
3. The nominal yield strength of the bolt material reaches 400×0.6=240 MPa level.
Performance grade 10.9 high-strength bolts, after heat treatment, can reach:
1. The nominal tensile strength of the bolt material reaches 1000MPa;
2. The yield strength ratio of the bolt material is 0.9;
3. The nominal yield strength of the bolt material reaches 1000×0.9=900MPa level
The meaning of bolt performance grade is an international standard. Bolts of the same performance grade have the same performance regardless of the difference in their materials and origins. Only the performance grade can be selected for design.
The so-called 8.8 and 10.9 strength grades mean that the shear stress grades of the bolts are 8.8GPa and 10.9GPa8.8, the nominal tensile strength is 800N/MM2, and the nominal yield strength is 640N/MM2
General bolts use "X.Y" to indicate strength, X*100=tensile strength of this bolt, X*100*(Y/10)=yield strength of this bolt (because according to the label: yield strength/tensile strength =Y/10)
Such as grade 4.8, the tensile strength of this bolt is: 400MPa; the yield strength is: 400*8/10=320MPa.
Another: stainless steel bolts are usually marked as A4-70, A2-70, the meaning is explained otherwise
Measurement: There are mainly two types of length measurement units in the world today, one is the metric system, and the measurement units are meters (m), centimeters (cm), millimeters (mm), etc., which are widely used in Southeast Asia such as Europe, my country, and Japan. The other is the imperial system, and the unit of measurement is mainly inches, which is equivalent to the old system in my country, and is widely used in the United States, the United Kingdom and other European and American countries. The public account "Mechanical Engineering Literature", a gas station for engineers!
1. Metric measurement: (decimal system) 1m = 100 cm = 1000 mm
2. Inch measurement: (octal system) 1 inch = 8 cents 1 inch = 25.4 mm 3/8¢¢×25.4 =9.52 3. Products below 1/4¢¢ use numbers to indicate their appellation diameter, such as: 4#, 5#, 6#, 7#, 8#, 10#, 12# thread
1. The thread is a shape with uniform helical protrusions on the cross-section of the outer or inner surface of a solid. According to its structural characteristics and uses, it can be divided into three categories:
(1) Ordinary thread: the tooth shape is triangular, which is used to connect or fasten parts. Ordinary threads are divided into coarse and fine threads according to the pitch, and the connection strength of fine threads is higher.
(2) Transmission thread: The tooth shape includes trapezoidal, rectangular, zigzag and triangular.
(3) Sealing thread: used for sealing connection, mainly pipe thread, tapered thread and tapered pipe thread.
2. Thread fit level:
Thread fit is the degree of looseness or tightness between screwed threads, and the degree of fit is the prescribed combination of deviations and tolerances acting on internal and external threads.
(1) For the unified British thread, there are three thread grades for external threads: 1A, 2A and 3A, and three grades for internal threads: 1B, 2B and 3B, all of which are clearance fits. The higher the grade number, the tighter the fit. In the inch thread, the deviation only stipulates grades 1A and 2A, the deviation of grade 3A is zero, and the grade deviation of grade 1A and grade 2A is equal. The larger the number of grades, the smaller the tolerance.
1, 1A and 1B grades, very loose tolerance grades, which are suitable for tolerance fit of internal and external threads.
2, 2A and 2B grades are the most common thread tolerance grades specified for imperial series mechanical fasteners.
3, 3A and 3B grades, screwed together to form the tightest fit, suitable for fasteners with tight tolerances, and used for safety-critical designs.
4. For external threads, grades 1A and 2A have a fitting tolerance, but grade 3A does not. Class 1A tolerances are 50% larger than Class 2A tolerances, 75% larger than Class 3A tolerances, and Class 2B tolerances are 30% larger than Class 2A tolerances for internal threads. Class 1B is 50% larger than Class 2B and 75% larger than Class 3B.
(2) For metric threads, there are three thread grades for external threads: 4h, 6h and 6g, and three thread grades for internal threads: 5H, 6H, and 7H. (The Japanese standard thread accuracy grade is divided into three grades: I, II, and III, and it is usually grade II.) In the 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 the picture shows:
1. H is the commonly used tolerance zone position for internal threads, and is generally not used as a surface coating, or a very thin phosphating layer is used. The basic deviation of the G position is used for special occasions, such as thicker coatings, and is generally rarely used.
2. g is often used to plate a thin coating of 6-9um. If the product drawing requires a bolt of 6h, the thread before plating adopts a tolerance zone of 6g. The public account "Mechanical Engineering Literature", a gas station for engineers!
3. The thread fit is best combined into H/g, H/h or G/h. For the thread of refined fasteners such as bolts and nuts, the standard recommends 6H/6g fit
(three), thread mark
Fourth, the main geometric parameters of self-tapping and self-drilling threads:
(1) The major diameter/tooth outer diameter (d1) is the diameter of the imaginary cylinder where the crests of the threads overlap. The thread major diameter basically represents the nominal diameter of the thread size.
(2) Minor diameter/root diameter (d2): It is the diameter of the imaginary cylinder where the thread bottom overlaps.
(3) Tooth pitch (p): It is the axial distance between adjacent teeth corresponding to two points on the mid-meridian. In the imperial system, the tooth distance is indicated by the number of teeth per inch (25.4mm).
The following table lists the common specifications of the tooth pitch (metric system) and the number of teeth (imperial system)
1. Metric self-tapping teeth:
Specifications: ST 1.5, ST1.9, ST2.2, ST2.6, ST2.9, ST3.3, ST3.5, ST3.9, ST4.2, ST4.8, S T5.5, S T6.3, S T8.0, S T9.5
Pitch: 0.5, 0.6, 0.8, 0.9, 1.1, 1.3, 1.3, 1.3, 1.4, 1.6, 1.8, 1.8, 2.1, 2.1 2. Inch self-tapping teeth:
Specifications: 4#, 5#, 6#, 7#, 8#, 10#, 12#, 14# Number of teeth: AB teeth 24, 20, 20, 19, 18, 16, 14, 14 A teeth 24, 20 , 18, 16, 15, 12, 11, 10
Specifications and standards - GB standards
Square head bolts Grade C GB 8-88 Countersunk head square neck bolts GB 10-88 Countersunk head tenon bolts GB 11-88 Half round head square neck bolts GB 12-88 Half round head tenon bolts GB 13-88
Large half-round head square neck bolts Grade C GB 14-1998 Large half-round head bolts with mortise GB 15-88
Cross recessed hex head bolts GB 29.2-88
Lower head bolts Grade B GB 35-88 Bolts for slots GB 37-88
Reinforced half-round head square neck bolts GB/T794-93 Swing bolts GB 798-88 Anchor bolts GB 799-88 Countersunk head double mortise screws GB 800-88
Small round half head low square neck bolts Grade B GB/T 801-1998
GB/T 9 0-1985 Acceptance Inspection, Marking and Packaging of Fasteners (eqvISO 3269:1984) GB/T 1 96-1981 Basic Dimensions of Ordinary Threads (Diameter 1-600mm) GB/T 1 97-1981 Ordinary Threads Tolerance and fit (diameter 1^355mm) GB / T 1237-2000 Marking method for fasteners (eqvI SO 8991:1986)
GB/T 3098.1-2000 Mechanical properties of fasteners Bolts, screws and studs (idtISO 898-1:1999) GB/T 3 103.1-1982 Tolerances of fasteners Bolts, screws and nuts (eqvI SO 4759-1:1978 ) GB /T 5267-1985 Electroplating coating for threaded fasteners
GB/T 5276-1985 Fastener bolts, screws, studs and nuts size codes and markings (eqvI SO 225:1983) GB/T 1 3912-1992 Technical requirements for hot-dip galvanized coating of steel products with metal coatings (neqI SO 1459 :1973)
GB/T 16938-1997 General specifications for fastener bolts, screws, studs and nuts (idtI SO 8992:1986) GB/T 18230.3-2000 Large hex nuts for bolted structures Grade B 8 and 10 (eqvI SO 4775 :1984) GB/T 18230.4-2000 Type 1 large hexagonal nuts for bolted structures, Grade B, Grade 10 (eqvISO 7414:1984) GB/T 18230.5-2000 Flat washers for bolted structures, quenched and tempered (neqISO 7416: 1984)
Bolt size standard (with photos)
1. The reference standard for inch bolts is ANSI/ASME B18.2.1, and the Japanese standard refers to JIS B1180 (Webster's thread). Inch system refers to BSW916 (Webster tooth).
(1) HEX MACHINE BOLT: no washer, with beam end, half tooth hexagonal bolt,
(2) HEX TAP BOLT: no washer, no beam end, full tooth hexagonal bolt,
(3) HEX CAP SCREWS: Hexagon bolts with washers, beam ends, and half teeth,
2. The reference standards for metric bolts are as follows, and their differences are shown in the table:
Old national standard New national standard ISO standard DIN (German standard) GB30
GB5780 (half tooth) GB5781 (full tooth) GB5782 (half tooth)
GB5783 (full teeth) ISO4016 ISO4018 ISO4014
ISO4017 DIN601 DIN558 DIN931
