What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
As my digital TV technology becomes more and more mature, more and more people with digital-to-analog signal conversion function enter people's lives. Therefore, the number of production and processing is also increasing day by day. There are many requirements for the form, reliability and cost of PCB fixing screws in production. One of the existing fixing methods is to fix by means of bolts and nuts. The operation steps are to place the PCB board on the inner threaded copper column connected to the casing, and pass through the bolts with fine teeth. Screw holes on the PCB board, and then fix them on the copper posts with nuts. The connection method of this solution is reliable, but its manufacturing cost is high, and the copper column and the metal shell need to be screwed together, resulting in low production efficiency and high cost. In addition, there is also a common way that the PCB is supported by a plastic column, and the self-tapping screw is passed through the screw hole on the PCB board, and the PCB board and the metal bottom shell are connected by the self-tapping thread on the screw. The main disadvantage of this solution is that after the screw is fixed on the metal shell, the screw head is exposed at the bottom of the machine. If the user is not careful during use, the hand scratching phenomenon will occur, which will bring changes and harm to the user's use. . And when the machine slides on the desktop, if the screw head is too exposed, it will scratch the desktop. Therefore, how to provide a PCB fixing method with convenient operation, reliable connection and low production cost is a technical problem to be solved urgently in the industry.
In chemical production equipment, the cylinder body and the head cover need to be connected and sealed. The traditional sealing structure is to connect the two with a screw, add a non-metallic gasket in the middle and fix it with a nut. However, such a sealing structure only controls the tightening torque, and has the technical defect that the sealing ring will be twisted or even broken during repeated loading and unloading of the cylinder head cover, resulting in poor sealing performance.
The process factors that affect the quality of high-strength fasteners include steel design, spheroidizing annealing, peeling and dephosphorization, drawing, cold heading, thread processing, heat treatment, etc., and sometimes the superposition of various factors.
Common types of common screws All kinds of common screws (20 pieces) a. Slotted: a word ( Minus ) b. Phillips: cross ( Plus ) c. Phil-Slot: a word / cross d. Hex Socket: hexagon socket e. One Way: One-way (can only be locked in, not out) A-4: Head Code/ head shape. a. Flat: Flat head (after locking, the top is flush with the work piece) b. Oval: salad head, O head, countersunk head screw unit of measure screw unit of measurec. Round: round headd. Pan: round flat heade. Truss: large round flat headf. Hex: hexagon head. A-5: Finish Code/Appearance treatment. Metric Self-tapping screw: Mark Tapping Type directly behind the product name. Ex: M3 x 6 –PPB, Tapping Type: M3 self-tapping screw, 6mm long, cross, round flat head, black plated. Generally, it is determined by product type or mark. For Sheet Metal or plastic parts. *Pitch = Threads per inch
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