What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
The hinge is a hinge, which is often composed of two folds. It is a part that connects the two parts of the object and can make it move. The hinge supporting screws are installed on the corresponding objects. For different use environments, the requirements for the supporting screws are also different. different. Most of the existing screws are set to a single-threaded structure. When used to cut into a wooden door, the cutting speed is slow, and the cutting effect is not ideal, which is not conducive to cutting into a hard wooden door, etc., and the commonly used screws are often made of iron materials. It is easy to rust after contact with water vapor, reducing the service life; in addition, when the screw is driven into the wooden door, the chips generated cannot be discharged in time, and stay inside the wooden door and surround the screw, forming expansion stress, thereby squeezing the wooden substrate, which is not conducive to the screw. The connection with the wooden door is stable, which easily affects the normal installation of the hinge, and the use effect is poor. To sum up, in order to solve the shortcomings of the existing screw structure for hinges, Guangdong Yueluo Hardware Industry Co., Ltd. designed a hinge screw with simple structure, convenient use, fast construction and good effect.
There is an anti-theft screw, which can prevent the use of any disassembly tool for disassembly, and effectively plays the role of anti-theft. Its structure is that the anti-theft screw is composed of two parts; the upper part is a hexagonal part, and the lower part is a threaded part; the hexagonal part and the threaded part are connected in rotation; The core shell is formed with the lock core; the lock core is rotatably connected with the lock core shell. The shell of the lock cylinder is fixedly connected with the hexagonal piece, and the starting structure is as follows: a pin hole is arranged on the hexagonal piece; The lower part of the hexagonal part is provided with a polygonal hole, which is connected with the polygonal hole on the threaded part; the lower part of the lock cylinder is a threaded rod; the threaded rod is located in the polygonal hole; The edge block moves up and down in the polygonal hole. When working, slowly twist the hexagonal piece from left to right and turn the key at the same time to achieve the alignment of the upper and lower polygonal holes.
In order to tighten the fastener, the holding element of the tightening tool can hold the washer in engagement with the bolt to prevent the washer from rotating while allowing the rotating element of the tightening tool to rotate the nut. Such tools are disclosed, for example, in Application Serial Nos. 0/010377 and 10/120343. In this structure, since the same size washer cannot be arranged on the driving part and the fixing part, the driving part is made into the inner socket of the nut, and the fixing part is made into the outer socket of the washer, so , regular hexagonal nuts cannot be used. This is because, when just tightening the nut, the outer cavity cannot be removed since the hexagonal surface of the nut will not align with the hexagonal surface of the washer. Due to the larger diameter of the fastener formed as the outer cavity, side clearance problems may arise, thus increasing the cross-sectional profile of the hexagonal surface of the washer, which is undesirable.
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
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