What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
Screws are a kind of fasteners commonly used in machinery, but most of the screws commonly used in the market are standard parts. The screws themselves are ordinary and have no function of preventing loosening and protecting the matrix. Therefore, in order to prevent the screws from loosening during use , Usually it is necessary to configure additional elastic washers, flat washers, etc. that are suitable for screws, and these elastic washers and flat washers are mostly metal products. During use, it is easy to wear with the body base and damage the protection of the sheet metal base. After long-term use, metal washers are easy to rust, which affects the tightening effect and appearance of screws. In addition, the use of metal washers not only increases the weight and cost, but also the assembly process is complicated and cumbersome, and the anti-loosening and anti-wear effects are not ideal. .
In the process of electronic accessories such as mobile phones and computers, especially multi-layer circuit boards, there are generally fixed connections between multi-layer circuit boards or other components. At present, there are two main connection methods. One is to use laser welding. However, the laser welding equipment is expensive and has very high requirements on the position of the weldment. Therefore, during welding, it must be ensured that the final position of the weldment needs to be the same as the laser beam will impact. Solder joint alignment. The other is to use a metal rivet to pass through the positioning hole, and then impact the rivet with a punching needle, so that the open end of the rivet is deformed and opened and pressed on the fixed piece to form a rivet fixed state. However, in actual operation, when the open end of the rivet tube is opened and deformed by the impact, strong cracking often occurs, resulting in a small amount of conductive fracture debris, which falls on the circuit board or other devices to be connected, causing Short circuit, in view of this shortcoming, some manufacturers have changed the metal rivets to plastic materials, but the plastic rivets have poor ductility and often break when impacted with a punching needle, resulting in the failure to achieve the riveting fixing force of the original metal rivets. In addition, the above two fixing methods are complicated in operation and low in installation efficiency.
At present, when using the existing screwdriver to install the screw, it is necessary to fix the screw with the left hand and turn the screwdriver with the right hand. However, in some places where the installation space is small and the installation is difficult, there are many areas that cannot be accessed by hands, and the installation is very difficult. For example, on an airplane, when installing with a common screwdriver, it is very difficult to install the screws and the installation efficiency is low because the screws cannot be positioned; in addition, when installing screws on the aircraft wing or fuselage, the combination between the screwdriver and the screw is easy to slip, The blade of the screwdriver slipped out and could easily bruise the hand and damage the aluminum skin of the aircraft.
The existing way to achieve radial locking of the shaft is generally to sleeve the positioning block on the shaft, and then use a cylindrical pin to pass through the positioning block to lock the shaft. The locking structure and method are as follows: A locking groove with an arc-shaped cross-section is set on the outer side of the shaft along the direction perpendicular to the axis of the shaft, an opening is set on the positioning block, and then a cylindrical pin is used to pass through the positioning block from the outside of the positioning block and screw the lock at one end of the cylindrical pin. When the lock nut is tightened, the opening on the positioning block will be deformed inwardly and locked on the shaft.
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