What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
Spring washers are widely used in the load-bearing and non-load-bearing structures of general mechanical products. They are characterized by low cost and easy installation. They are suitable for parts with frequent assembly and disassembly. Quick and easy automatic selection of washers is included, but the anti-loosening ability of spring washers is very low! Especially in European and American countries that require high reliability, the adoption rate is extremely low, especially the important load-bearing structural connection parts have long been abandoned. Our country still has some applications in the military industry, but it has been improved to stainless steel. Steel spring washers have long been banned in CASC! It is also said to be very unsafe, because there are two reasons: 1 is circle rise and 2 is hydrogen embrittlement.
According to the design of the screw washer 110 , when the metal piece 120 and the metal piece 130 are disassembled, after the screw 100 is loosened, the screw washer 110 is often easily dropped or lost, causing trouble for maintenance. Especially when replacing parts at the user end, if the screw washer is loose, it cannot ensure that the user can install it correctly; if the screw washer is lost, it is necessary to purchase new parts, causing a lot of inconvenience.
When the mechanical components are installed on the concrete foundation, the J-shaped and L-shaped ends of the bolts are embedded in the concrete for use. The tensile capacity of the anchor bolt is the tensile capacity of the round steel itself. The size is equal to the cross-sectional area multiplied by the allowable stress value (Q235B: 140MPa, 16Mn or Q345: 170MPA), which is the allowable tensile capacity at the time of design. The anchor bolts are generally made of Q235 steel, which is smooth and round. Rebar (Q345) is strong, and the thread of the nut is not as easy to be round. For light round anchor bolts, the burial depth is generally 25 times its diameter, and then a 90-degree hook with a length of about 120mm is made. If the bolt diameter is large (such as 45mm) and the buried depth is too deep, a square plate can be welded at the end of the bolt, that is, a large head can be made (but there are certain requirements). The burial depth and hook are all to ensure the friction between the bolt and the foundation, so as not to cause the bolt to be pulled out and damaged.
The head of the traditional screw is located outside the threaded hole and occupies a large space, which is not suitable for occasions with small space, nor is it suitable for occasions where the outer surface of the component is a working surface. For example, in the field of electronic products, or when connecting the shaft and the shaft sleeve, the machine screw with a fully threaded structure on the outer surface is widely used.
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