What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
The performance grade is divided into 15 grades, stainless steel is grade 51, and the open type blind rivet is divided into two types: countersunk head and flat round head according to the shape of the head. Among them, open blind rivets with performance levels of 10 and 11 are widely used. In 2006, the National Standards Committee revised and released GB/T 12617.1-2006 Open Type Countersunk Head Blind Rivets Class 10 and 11 and GB/T 12618.1-2006 Open Type Flat Round Head Blind Rivets Class 10 and 11. National standards for 10 and 11 class open blind rivets. The two new standards, respectively adopting ISO15978:2002 and ISO15977:2002 international standards, were released on July 5, 2006 and officially implemented on December 1, 2006. After implementation, it will replace the two old standards GB/T 12617-1990 Open Type Countersunk Head Blind Rivets and GB/T 12618-1990 Open Type Oblate Head Blind Rivets.
The meaning of bolt performance grade is an international standard. Bolts of the same performance grade, regardless of the difference in material and origin, have the same performance, and only the performance grade can be selected in the design. Strength grade The so-called 8.8 and 10.9 grades refer to the shear stress grades of bolts of 0.88GPa and 1.09GPa 8.8 Nominal tensile strength 800N/MM2 Nominal yield strength 640N/MM2 General bolts use XY to indicate the strength, X *100=tensile strength of this bolt, X*100*(Y/10)=yield strength of this bolt (because according to the regulations: yield strength/tensile strength=Y/10, that is, 0.Y is the yield strength ratio ) If the grade is 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, and the meaning is otherwise explained Measurement: There are two main units of length measurement in the world today, one is the metric system, and the measurement unit is meters (m) and centimeters (cm). ), millimeter (mm), etc., are used more in Europe, my country and Japan and other Southeast Asian regions, the other is the British system, and the unit of measurement is mainly inches (inch), which is used more in the United States, Britain and other European and American countries. 1. Metric measurement: (decimal system) 1m2 =100 cm2=10000 mm2, imperial measurement: (8 decimal system) 1 inch = 8 inches 1 inch = 25.4 mm 3/8¢¢×25.4 =9.523, 1/4 ¢¢ The following products are indicated by their number, such as: 4#, 5#, 6#, 7#, 8#, 10#, 12#
The existing structure is found in the practical application experience that there are still the following problems and drawbacks: the screw structure and the screw space are combined with each other in a complementary manner, so they can provide a higher torque value, however, not every workpiece. The combination requires a high torque value, so it often results in excess quality. Although the price of the screw is low, if it can change the unchanging structure of the traditional screw, it can provide a technical means to simplify (change) the process. The effect of improving production capacity and convenience of use is indeed a technical bottleneck that the relevant industry should break through.
Pins are widely used. In the connection of the rotating mechanism of two moving components, such as the crank mechanism, the turning mechanism, the connection between the hydraulic cylinder and the moving parts, the pins are used. kind. In order to ensure the normal use of the running equipment and prevent the cylindrical pin from slipping out and falling off during use, some anti-falling methods are usually used at the head of the pin, such as 1. Drill holes and insert cotter pins to prevent the pins from slipping out; 2. The external thread is tightened with a nut to prevent the pin from slipping out; 3. The slot is clamped with a circlip to prevent it from slipping out, etc. These measures make the cylindrical pin very practical in the case of infrequent disassembly and assembly, but in the actual use of the field, in order to prevent the collision of some equipment during each troubleshooting or maintenance, the pin needs to be pulled out and turned up, etc. After the failure or maintenance is completed, put down and then insert the pin to restore, this process will bring trouble to the actual operator. For example, special tools must be brought with you every time you disassemble and assemble the pin, and the split pin or the circlip is easily damaged after repeated disassembly and assembly. , In order to save trouble, the operator sometimes uses iron wire to thread or fasten it instead, and even does not remove the pin for the sake of speed and convenience, which is easy to cause damage to the equipment when dealing with faults.
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