Screws are commonly called "screws".
The shape of the nut is usually hexagonal, and the inner hole is an internal thread, which is used to cooperate with the bolt and tighten the related parts.
The difference between screws, nuts, nuts, bolts, screws, and studs
The standard statement is that there are no screws and nuts.
Screws are commonly called "screws".
The shape of the nut is usually hexagonal, and the inner hole is an internal thread, which is used to cooperate with the bolt and tighten the related parts.
The nut is commonly called, and the standard should be called "nut".
The head of the bolt is generally hexagonal, and the shank has an external thread.
The screw is small, the head has a flat head, a cross head, etc., and the rod has an external thread.
The actual stud should be called "double-ended stud", both ends have external threads, and the middle is generally a polished rod. The long end of the thread is used to connect to the deep hole, and the short end is connected to the nut.
Definition of thread
Thread is a shape with uniform spiral lines on the outer or inner surface of a solid.
Thread effect
1. Fastening and connection function: suitable for most screw products at this stage.
2. Transmission function (displacement function): such as a micrometer used for QC check size.
3. Sealing function: such as the sealing of the connection of the pipeline.
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 bolts of grade 8.8 and above are made of low-carbon alloy steel or medium-carbon steel and are heat-treated (Quenching and tempering), commonly known as high-strength bolts, and the rest are commonly known as ordinary bolts. The bolt performance grade label consists of two numbers, which respectively indicate the nominal tensile strength value and the yield ratio of the bolt material. E.g:
Bolts of performance class 4.6, its meaning is
The nominal tensile strength of the bolt material reaches 400MPa; the yield ratio of the bolt material is 0.6; the nominal yield strength of the bolt material reaches 400×0.6=240MPa.
Performance grade 10.9 grade high-strength bolts, after heat treatment, can reach:
The nominal tensile strength of the bolt material reaches 1000MPa;
The yield ratio of the bolt material is 0.9;
The nominal yield strength of the bolt material reaches 1000×0.9=900MPa level.
The meaning of the bolt performance grade is the international standard. The bolts of the same performance grade, regardless of the difference in material and origin, have the same performance. Only the performance grade can be selected in the design.
Measure
There are two main 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 more commonly used in Southeast Asia such as Europe, my country and Japan, and the other The species is in the British system, and the measurement unit is mainly inches (inch), which is equivalent to the market inch of my country's old system, and is used more in the United States, Britain and other European and American countries.
Metric measurement: (decimal system) 1m =100 cm=1000 mm
Imperial measurement: (octal system) 1 inch = 8 cents 1 inch = 25.4 mm
Products below 1/4 are designated by designations, such as: 4#, 5#, 6#, 7#, 8#, 10#, 12#
Thread
Thread is a shape with uniform helix protrusions on the cross-section of the solid outer or inner surface. According to its structural characteristics and uses, it can be divided into three categories:
Ordinary thread: the tooth shape is triangular, 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.
Transmission thread: the tooth shape includes trapezoid, rectangle, saw and triangle.
Sealing thread: used for sealing connection, mainly pipe thread, taper thread and taper pipe thread.
Thread fit grade
Thread fit is the size of looseness or tightness between screwed threads, and the level of fit is used in the specified combination of deviations and tolerances on internal and external threads.
For unified inch threads, 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 level number, the tighter the fit. In the inch thread, the deviation is only specified for 1A and 2A grades, the deviation of 3A grade is zero, and the grade deviations of 1A and 2A grades are equal. The larger the number of levels, the smaller the tolerance.
1A and 1B grades, very loose tolerance grades, which are suitable for tolerance matching of internal and external threads.
Grades 2A and 2B are the most common thread tolerance grades specified for inch series mechanical fasteners.
3A and 3B grades, the screwing forms the tightest fit, suitable for tight tolerance fasteners, and is used for the key design of safety.
For external threads, 1A and 2A have a matching tolerance, and 3A does not. The 1A tolerance is 50% larger than the 2A tolerance and 75% larger than the 3A tolerance. For internal threads, the 2B tolerance is 30% larger than the 2A tolerance. Class 1B is 50% larger than Class 2B and 75% larger than Class 3B.
For metric threads, there are three thread grades for external threads: 4h, 6h and 6g, and three thread grades for internal threads: 5H, 6 H, and 7H. (Japanese standard thread accuracy grades are divided into three grades: I, II, and III. Normally, it is grade II.) In metric threads, 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.
H is the commonly used tolerance zone position for internal threads. Generally, it is not used as a surface coating, or a very thin phosphating layer is used. The basic deviation of G position is used in special occasions, such as thicker plating, which is generally rarely used.
g It is commonly used to plate a thin coating of 6-9um. For example, the product drawing requires a 6h bolt, and the thread before plating adopts a tolerance zone of 6g.
The thread fit is best combined into H/g, H/h or G/h. For refined fastener threads such as bolts and nuts, the standard recommends the use of 6H/6g fit.
Main geometric parameters of self-tapping and self-drilling threads
1. Major diameter/tooth outer diameter (d1): It is the diameter of the imaginary cylinder where the thread crest overlaps. The major diameter of the thread basically represents the nominal diameter of the thread size.
2. Minor diameter/bottom diameter (d2): the diameter of the imaginary cylinder where the thread bottom overlaps.
3. Tooth pitch (p): It is the axial distance between two adjacent teeth corresponding to two points on the middle meridian. In the imperial system, the number of teeth per inch (25.4mm) is used to indicate the pitch.
The following lists the common specifications of the pitch (metric system) and the number of teeth (imperial system)
(1) Metric system self-tapping:
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
Tooth 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:
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
Dongguan Qisheng Metal Technology Co., Ltd. is a professional manufacturer of screws and nuts and other fastener products integrating R&D, production, processing and sales. Specializing in the production of special precision screws and nuts of various standards such as national standard GB, Japanese standard JIS, British BS, American ANSI, ISO and so on. Our products can meet the environmental testing standards of the European Union, the United States, Japan and other countries, and even more stringent testing standards. Look forward to working with you!
