What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
The use of stainless steel screw lines: The hardness of stainless steel screw lines causes them to have different uses. Generally, they are used as small screws in life, but also as car screws and compression screws. They are widely used in normal life. Types of stainless steel screw lines: In appearance, screw lines are generally divided into fog surface spring lines and bright surface screw lines. The hardness of matte surface screw lines is higher than that of bright surface screw lines. For products with low appearance requirements and relatively high elasticity requirements. Paper, oxalic acid, fertilizer and other production equipment; photography, food industry, facilities in coastal areas, ropes, CD rods, bolts, nuts.
Pedicle screws can be divided into four types: one-way short-tail screw, one-way long-tail screw, universal short-tail screw and universal long-tail screw. Pedicle screws can effectively complete the three-column fixation of the spine and are clinical The most widely used internal fixation method for the treatment of spine-related diseases. Due to the different types of pedicle screws, four different screwdrivers are required to complete the screw insertion. However, the implantation of pedicle screws is performed in a complex three-dimensional space, which has high difficulty and risk. Mis-implantation of screws may cause instability of the internal fixation frame in the early stage, and may cause false joint formation in the later stage. Therefore, in the process of spinal internal fixation, it is necessary to ensure the accurate implantation of pedicle screws is the key to the success of the entire spinal internal fixation, and the selected implanted instruments are particularly important.
Type 1) Slotted ordinary screws are mostly used for the connection of smaller parts. It has pan head screws, cylinder head screws, countersunk head screws and countersunk head screws. The head strength of pan head screws and cylinder head screws is high, and they are connected to common parts; the head of semi-countersunk head screws is arc-shaped, and its top is slightly exposed after installation, and it is beautiful and smooth. It is generally used for instruments or Precision machinery; countersunk head screws are used where the nail head is not allowed to be exposed. 2) The head of the hexagon socket head cap screw and the hexagon socket head flower screw can be embedded in the component, which can apply a large torque and have a high connection strength, which can replace the hexagonal bolt. It is often used in joints where compact structure and smooth appearance are required. 3) Cross recessed ordinary screws have similar functions to slotted ordinary screws, and can be replaced by each other, but the cross recessed ordinary screws have higher groove strength, are not easy to be bald, and have a more beautiful appearance. When using it, it must be loaded and unloaded with the matching cross-shaped screwdriver. 4) Lifting ring screw Lifting ring screw is a kind of hardware accessories for load-bearing during installation and transportation. When in use, the screw must be screwed in to the position where the supporting surface is tightly fitted, and tools are not allowed to be tightened, nor is a load perpendicular to the plane of the lifting ring allowed to act on it. 5) Set screws Set screws are used to fix the relative position of the parts. Screw the set screw into the screw hole of the part to be fastened, and press its end against the surface of the other part, that is, to fix the former part on the latter part. Set screws are usually made of steel or stainless steel, and their end shapes are conical, concave, flat, cylindrical and stepped. The end of the tapered or concave end set screw directly presses the parts, and is generally used in places that are not often disassembled after installation; the end of the flat end set screw is smooth and does not damage the surface of the parts after tightening, and is used for frequent adjustment of the position. At the connection, only a small load can be transmitted; the cylindrical end fixing screw is used in the fixed position that needs to be adjusted frequently, it can withstand a large load, but the anti-loosening performance is poor, and anti-loosening measures should be taken when fixing; Set screws are suitable for fixing parts with thicker walls. 6) Self-tapping screws When self-tapping screws are used on the connected parts, threads may not be pre-made at the connected parts. Use the screw to tap the thread directly when connecting. It is often used to join thin metal plates. There are two types of taper end tapping screws and flat end tapping screws. 7) Self-tapping locking screw Self-tapping locking screw not only has self-tapping effect, but also has low screw-in torque and high locking performance. Its thread is a triangular section, and the surface of the screw is hardened and has high hardness. Its thread specifications are M2 ~ M12.
At present, the standard parts on the market mainly include carbon steel, stainless steel and copper. A carbon steel. We distinguish low carbon steel, medium carbon steel and high carbon steel and alloy steel by the content of carbon in carbon steel material. 1 Low carbon steel C%≤0.25% is usually called A3 steel in China. Foreign countries are basically called 1008, 1015, 1018, 1022, etc. Mainly used for grade 4.8 bolts, grade 4 nuts, small screws and other products without hardness requirements. (Note: 1022 material is mainly used for drill tail screws.) 2 Medium carbon steel 0.25% 3 High carbon steel C%>0.45%. 4 Alloy steel is basically not used in the market: alloying elements are added to ordinary carbon steel to increase some special properties of steel: such as 35, 40 chromium molybdenum, SCM435, 10B38. Fangsheng screws mainly use SCM435 chromium molybdenum alloy steel, the main components are C, Si, Mn, P, S, Cr, Mo. Two stainless steel. Performance grade: 45, 50, 60, 70, 80 1 Mainly divided into austenite (18% Cr, 8% Ni) with good heat resistance, good corrosion resistance and good weldability. A1, A2, A4 2 Martensite, 13%Cr have poor corrosion resistance, high strength and good wear resistance. C1, C2, C4 ferritic stainless steels. 18%Cr has better upsetting and corrosion resistance than martensite. The imported materials on the market are mainly Japan. According to the level, it is mainly divided into SUS302, SUS304 and SUS316. Three coppers. Commonly used materials are brass...zinc-copper alloys. The market mainly uses H62, H65, H68 copper as standard parts.
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