What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
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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In the manufacture of fasteners, the correct selection of fastener materials is an important part, because the performance of fasteners is closely related to its materials. If the material is improperly or incorrectly selected, the performance may not meet the requirements, the service life may be shortened, or even accidents or processing difficulties may occur, and the manufacturing cost will be high. Therefore, the selection of fastener materials is a very important link. Cold heading steel is a steel for fasteners with high interchangeability produced by cold heading forming process. Because it is formed by metal plastic processing at room temperature, each part has a large amount of deformation and a high deformation speed. Therefore, the performance requirements of cold heading steel raw materials are very strict. On the basis of long-term production practice and user research, combined with GB/T6478-2001 Technical Conditions for Cold Heading and Cold Extrusion Steel GB/T699-1999 High-Quality Carbon Structural Steel and target JISG3507-1991 Cold Heading Characteristics of Carbon Steel Wire Rod for Steel, taking the material requirements of grade 8.8 and grade 9.8 bolts and screws as an example, the determination of various chemical elements. If the C content is too high, the cold formability will be reduced; if it is too low, the mechanical properties of the parts cannot be met, so it is set at 0.25% - 0.55%. Mn can improve the permeability of steel, but adding too much will strengthen the matrix structure and affect the cold forming performance; when the part is quenched and tempered, it has the tendency to promote the growth of austenite grains, so it should be appropriately improved on the basis of international standards. 0.45 % - 0.80 %. Si can strengthen the ferrite and reduce the cold formability. SP is an impurity element, and their existence will cause segregation along the grain boundary, resulting in the embrittlement of the grain boundary and damage to the mechanical properties of the steel. It should be reduced as much as possible. B. The maximum value of boron content is 0.005%, because although boron element can significantly improve the permeability of steel, it will also increase the brittleness of steel. Excessive boron content is very unfavorable for workpieces such as bolts, screws and studs that require good comprehensive mechanical properties.
T-bolt with a spring, used for undercutting the opening of the outer closed cavity, including a head and a rod part connected in one piece, and also including a strip spacer, a spring and a pull rod, and the length of the strip spacer is greater than The opening, the connecting part of the head and the rod part are set as polygonal anti-rotation blocks, and the strip-shaped spacer is provided with anti-rotation holes for inserting the anti-rotation blocks, and the shape and size of the anti-rotation holes are the same as The size of the anti-rotation hole is smaller than that of the head; the spring is threadedly matched with the rod part, and is fixedly connected with the pull rod, and the pull rod moves away from the rod part along the axial direction of the rod part One side of the head extends. The utility model can be easily and reliably buckled in the opening of the airtight cavity, thereby facilitating the installation and connection of external parts.
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