What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
① Nominal thread outer diameter (thread specification): divided into metric system and inch system. Metric thread → common specifications are 2; 2.3; 2.5; 2.6; 2.9; 3; 3.1; 3.5; 4; 4.2; 4.5; The unit is mm (millimeters). Inch thread→ Common specifications are 2#;4#;6#;8#;10#;12#;1/4;7/32;5/16;3/8;1/2 ;9/16;3/ 4. The unit is in (inches). ② Number of teeth/pitch: Definition of number of teeth → the number of teeth lines in one inch (25.4mm) length. Pitch Definition → Distance value between two adjacent threads. Conversion of number of teeth and pitch of teeth → pitch of teeth = 1 inch/number of teeth ③Nominal length: divided into metric system and inch system. Metric Nominal Length → Common values are 5, 6, 6.5, 7, 8, 9, 9.5, 10, 11, 12, 13, 14, 15, 16, 18, 19, 20, 21, 25, 28, 30, 31 , 32, 35, 40, 42, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 110, 120. The unit is mm (millimeters). Imperial Nominal Length → Common values are 1/4, 5/16, 3/8, 7/16, 1/2, 5/8, 3/4, 1, 2, 3. Units: in (inches). ④Head type: use letters to indicate the type of head type, please refer to the previous classification of commonly used screw head types. ⑤Tooth type/tail type: Use letters to indicate the type of tooth type/tail type, please refer to the previous Commonly used screw thread/tail type classification. ⑥Groove type: Please refer to the previous section Category of common screw groove types of our company. Cross-slotted or non-slotted (such as punched hexagon head screws) do not need to be marked here, and other groove types need to be described in words. ⑦Special labeling: In general, no labeling is required. When expressing its characteristics, it is described in words at this position. For example: the specification name of the screw is described as 4-0.7x70PM±tooth length 35, which means 4 is the nominal diameter of the screw thread, 0.7 is the pitch, 70 is the nominal length of the screw, and P means its The head type is a pan head, M means its tooth type/tail type is a wire thread type, ± means its groove type is ± groove and can also be expressed by plus or minus groove. Tooth length 35 is special Mark, specify the thread length value of this screw.
A screw suitable for a variety of tools is a single-structure threaded part, including a screw body and a screw head. The outer surface of the screw body is processed with an external thread 1, and the outer side of the screw head is formed by six screw heads. Prismatic, the top surface of each edge of the outer hexagonal prism is a boss, between each boss is an end face groove 4, and the middle of each boss is provided with an end face hole 3; the inner side of the screw head is formed by six screw heads. The side surface 5 forms an inner hexagonal prism hole, and the bottom of the inner hexagonal prism hole is processed with a cross groove 16 .
The research on rivet nuts started in the 1970s in my country and is still in the design and development stage. In the mid-1980s, equipment for the production of blind rivets was introduced from abroad, but no rivet nut has been produced so far. After the inventor's search, no low-carbon steel rivet nut was found to be publicly used.
T-bolts for channel steel usually include a head and a shank. The shank is provided with threads. Traditional T-bolts for channel steel are used for channel steel, and both channel steel and bolts are made of steel. , the two are prone to thermal expansion and contraction due to changes in the external ambient temperature, and are prone to loosening, resulting in unstable connections.
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