What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
Spring washers are often called spring washers in the screw industry. Its materials are stainless steel and carbon steel, and carbon steel is also iron. The commonly used spring washers are M3, M4, M5, M6, M8, M10, M12, M14, M16. These specifications are more commonly used. The national standard for spring washers is GB/T 94.1-87, which specifies standard spring washers with a size of 2-48mm. Reference standard GB94.4-85 Elastic Washer Technical Conditions Spring Washer
The existing machine screw structure is not conducive to assembly and automated production. The machine screw is in the form of a cylinder, the outer surface of the cylinder is provided with threads, and one end of the machine screw is provided with a notch. During installation, it is convenient to rotate the machine screw by the tool acting on the notch, so that the machine screw all enters the threaded hole and does not occupy the external space. However, the thread on the outer surface of the machine screw corresponding to the slot is easily deformed or scratched due to the external force of the tool and the threaded hole, which makes it difficult to screw in or disassemble, and reduces the versatility and interchangeability. affect product quality.
Existing wood screws are composed of a threaded portion with a tapered angle and arranged along a tapered stem and a screw head. The head of the screw can be a countersunk head, hemispherical, or other shapes, and the head of the screw has a groove that fits with the tool, a word groove, and a concave cross groove. The taper angle of existing wood screws is either 45 degrees or 60 degrees, and the front end of the taper angle is a pointed point formed by a rotating thread. The existing wood screws have the following three deficiencies in use. Because the taper angle is 45 degrees or 60 degrees, and the thread angle is 64 degrees, the resistance when entering the material is relatively large, so the existing wood screws are manually screwed. It is difficult to screw in, especially when it is used for hardwood materials, and it often happens that the groove of the screw head is screwed out; A large lateral moment will be formed when the screw is screwed, which is prone to the problem of deviation from the position; in addition, because the existing screw is tapered, it will be subjected to both radial force and axial force when entering the material, and its stress state It is more complicated, so it is easy to cause the cracked wood material to burst, and even cause the material to have longitudinal cracks and be unusable.
Now people often use spring washers to lock nuts and bolts, spring washers, generally stainless steel and carbon steel non-closed spiral washers, under the nut, above the flat washer, increase the friction between the nut and the bolt, used to prevent The loosening of the nut plays a role in preventing vibration and loosening, but it is often due to a radial external tension, which is caused by the tightening axial force generated by the tightening torque, and the phenomenon of open ring expansion occurs, and the hydrogen embrittlement of the spring washer often occurs. The pressure is unevenly applied to the flat washer through the spring washer, and the friction coefficient between the spring washer and the nut and the flat washer is small, resulting in vibration, rotation and relaxation.
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