What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
As shown in FIG. 1 and FIG. 2 , a rivet die in the prior art includes a set of top die 1 and cover die 2 arranged opposite to each other. The top die 1 is provided with a cavity 1 in the center that matches the shape of the rivet dome head 3-1. -1, the center of the cover mold 2 is provided with a mold cavity 2-1 that matches the shape of the rivet dome head 3-3.
At present, there are mainly the following methods for classifying screws of different lengths mixed together: First, visual identification and manual sorting. This method is time-consuming, labor-intensive and inefficient. Second, the screws are centrifuged and screened according to the quality and size of the screws. However, the quality of screws of the same length is not necessarily the same when the materials of the screws are different. Third, sorting is carried out using a screening device with sieve holes, but the sieve holes are generally simple geometric shapes, which can only roughly distinguish the length of the screws. Moreover, the specific position where the screw falls into the screen hole will also affect the degree of screening. It can be seen that the above-mentioned methods for classifying screws all have the problem of poor effect.
At present, the electrical control boxes of the market regulators all include a box body with built-in circuit board components and a box cover that is fastened together with it. The box cover is mostly fastened on the box body by self-supplied screws. The following problems are: First, there are many electric control lines on the circuit board in the box. When installing the self-supplied screws, the electric control lines may be damaged, which may easily cause a short circuit of the electric control, which is a potential safety hazard; Electric batch and other tools are inconvenient to install and disassemble, and the production cost is high.
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.
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