What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
There is a standard for the outer hexagon bolt standard, which is a grade standard, which is divided into grade 4.8 and grade 8.8. These two levels are used a lot in the market. Especially grade 4.8 hex head bolts. Because it is much cheaper than 8.8 hex bolts. Of course it is more widely used. But for demanding products. Because of its high requirements in various aspects such as hardness. This requires the use of 8.8 hex bolts. Grade 8.8 hex bolts are harder in terms of hardness and screw torque. It is safer to use the product. Tighter and more stable.
Yueluo - a screw and nut disassembly tool for a narrow space, including a sleeve rod, a sleeve rod vertically arranged at one end of the sleeve rod, a connecting rod for fixedly connecting the sleeve rod and the sleeve rod, and a sleeve rod located at the end of the sleeve rod. The connecting rod in the axial through hole of the sleeve rod, the connecting rod located in the axial through hole of the sleeve rod, and the bearing for fixedly connecting the sleeve rod and the connecting rod and making the connecting rod rotate stably in the sleeve rod , and a sleeve head arranged at one end of the connecting rod, the connecting rod and the adjacent end of the connecting rod are provided with gears and the two gears are vertically meshed, so that when the external force drives the connecting rod to rotate, the force passes through The two gears and the connecting rod are transmitted to the sleeve head, thereby driving the screw or nut in the sleeve head to rotate;
The performance grade 8.8 of stainless steel bolts refers to the material's tensile strength limit of 800MPa and yield limit of 640MPa. The performance grades of stainless steel bolts, studs and studs are divided into 10 grades: from 3.6 to 12.9. The number before the decimal point represents 1/100 of the tensile strength limit of the material, and the number after the decimal point represents 10 times the ratio of the material's yield limit to the tensile strength limit. There are 7 grades of performance grades for nuts, from 4 to 12. The numbers roughly represent 1/100 of the minimum stress that the stainless steel nut is guaranteed to withstand. For unified inch threads, there are three thread grades for external threads: grades 1A, 2A and 3A, and three grades for internal threads: grades 1B, 2B and 3B, all of which are clearance fits. The higher the rating number, the tighter the fit. Classes 1, 1A and 1B, very loose tolerance classes, which are suitable for tolerance fits of internal and external threads. Grades 2, 2A and 2B are the most common thread tolerance grades specified for inch series mechanical stainless steel fasteners. Grades 3, 3A and 3B, screwed together to form the tightest fit, suitable for tight tolerance stainless steel standard parts, for safety critical designs. Metric threads, there are three thread grades for external threads: 4h, 6h and 6g, and three thread grades for internal threads: 5H, 6H, 7H. Thread fit is best combined into H/g, H/h or G/h. For bolts, stainless steel nuts and other refined fastener threads, the standard recommends 6H/6g fit. Carbon steel: The strength grade is marked by ? It consists of two separated numbers. The meaning of the number part before the ? in the marking code represents the nominal tensile strength, for example, 4 in grade 4.8 represents 1/100 of the nominal tensile strength of 400N/MM2. The meaning of the ? and the number part after the point in the marking code represents the yield-strength ratio, that is, the ratio of the nominal yield point or the nominal yield strength to the nominal tensile strength. For example, the yield point of grade 4.8 products is 320N/mm2. The strength grade mark of stainless steel products consists of two parts separated by —. The symbol before — in the sign code indicates the material. Such as: A2, A4 and other signs — indicate strength, such as: A2-70 Carbon steel: The mechanical properties of bolts can be divided into: 3.6, 4.6, 4.8, 5.6, 5.8, 6.8, 8.8, 9.8, 10.9, 12.9 in total 10 performance levels
Screw refers to a screw, which is a tool that uses the physical and mathematical principles of the inclined plane, circular rotation and friction of an object to gradually fasten objects and parts. A screw is a common term for fasteners. Fasteners are widely used in machinery, electrical appliances and buildings. They are generally made of metal or plastic, cylindrical in shape, and grooves engraved on the surface are called threads.
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