What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
Anti-corrosion technology Stainless steel screws are made of metal, and there are four main methods for metal anti-corrosion, namely the properties of the material itself, the environment of use, the interface between materials and the environment, and the improvement of the metal structure design. If a complete anti-corrosion alloy is used to make stainless steel Screws, unless there is a special need, are not cost-effective in terms of economics, and it is also impractical to completely isolate the appearance of the screw from environmental elements that can cause corrosion. Improving the metal structure design can improve the influence of special circumstances under certain conditions, but the design of most stainless steel screws cannot be fully corrected, and its maintenance effect is not permanent, so this method cannot basically solve the problem, as long as it is on the surface. Top anti-corrosion, that is, surface anti-corrosion treatment is the most widely used method. The anti-corrosion treatment on the surface of stainless steel screws refers to the use of various methods to apply a protective layer on the metal surface. The purpose of avoiding or mitigating corrosion. The protection layer should be able to meet the following requirements: 1. Corrosion resistance, wear resistance, high hardness, 2. The structure is tight, intact, and the pores are small. 3. It has strong separation and good adhesion with the base metal. 4. It is evenly distributed and has a certain thickness. The maintenance layer is usually divided into two types: metal coating and non-metallic coating. Metal coating refers to the use of metal or alloy with strong corrosion resistance to form a maintenance layer on the surface of metal that is easy to corrode. This coating is also called plating. There are quite a few methods and varieties to produce metal coatings, the most common of which is electroplating, followed by molten metal immersion plating (hot dipping) and chemical surface treatment. Non-metallic coating refers to the use of organic polymer materials such as paint and inorganic materials such as ceramics to form a protective layer on the surface of metal equipment or parts. The protective layer can completely isolate the base metal from the environmental medium and prevent the base metal from corrosion due to contact. Corrosion is formed in the medium of stainless steel standard parts.
On the other hand, especially in the aerospace field, the requirements for the sealing effect of screws are extremely strict, and the traditional screws are directly tightened when screwed into the workpiece or equipment, and the sealing effect is determined by the tightness, but due to the machining error of the workpiece or equipment The direct butt seal between the seals is difficult to achieve.
For hexagonal nuts, the commonly used standards are: GB52, GB6170, GB6172 and DIN934. The main differences between them are: the thickness of GB6170 is thicker than that of GB52, GB6172 and DIN934, commonly known as thick nuts. The other is the difference between the opposite sides, the opposite sides of DIN934, GB6170 and GB6172 in the M8 nut series are 13MM smaller than the opposite side 14MM of GB52, and the opposite sides of M10 nuts, DIN934 and GB52 are 17MM. The opposite side of GB6170 and GB6172 should be 1MM larger, M12 nut, DIN934, GB52's opposite side is 19MM larger than GB6170 and GB6172's opposite side 18MM is 1MM larger. For M14 nuts, the opposite side of DIN934 and GB52 is 22MM, which is 1MM larger than the opposite side of GB6170 and GB6172, which is 21MM. The other is the M22 nut. The opposite side of DIN934 and GB52 is 32MM, which is 2MM smaller than the opposite side of GB6170 and GB6172, which is 34MM. (Besides the thickness of GB6170 and GB6172 are the same, the width of the opposite side is exactly the same) The rest of the specifications can be used in general without considering the thickness.
A screw can be equipped with only one spring washer or only one flat washer, or it can also only be equipped with a two-piece combination of flower teeth. The national standard number of the combination screw is represented by GB9074. The commonly used cross recessed small pan head three combination screw national standard is GB9074.8. This .8 refers to the small pan head. That is, the size of the head of the pan head screw that is often said. Denoted by letters as PM. Professional combination screw manufacturers, the habitual expression method is three-in-one PM. The commonly used cross recessed large pan head combination screw national standard is GB9074.4. Professionally called large pan head combination screws. Or R head, or B head. That is to say, the head of this combination screw is larger and thicker than the head of the small pan head combination screw. There is also a commonly used external hexagon combination screw, which is a cross external hexagon combination screw. It is often called a socket hexagon combination screw. The national label is GB9074.13.
The above content is uploaded by Yueluo or the Internet. If there is any copyright issue, please contact [email protected].
