What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
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.
At present, injection molding screws are widely used in various electronic and automotive components, including a body, the middle of which is provided with a through hole 3, the body head 1 has a hexagonal cross-section, and the tail 2 is provided with screw teeth. When in use, the middle through hole 3 of the main body will first put the wire harness, and then fix it by injection molding from the head I, and the threads of the tail 13 should be connected and installed with other components. Because the head I of the main body is hexagonal, the torque provided after injection molding is insufficient. Therefore, after the external thread is installed and connected with other components, the head is prone to slip, the installation is not reliable, and there is no push-pull force, resulting in product failure and increased safety hazards.
It can be seen that the above processing method can only be used to process a relatively simple retaining ring (that is, only a ring body, which cannot be cut or punched), and the outer surface of the processed retaining ring still cannot be guaranteed to be completely flat.
The common types of wood screws are iron and copper, and the types are divided into round head type and other samples of wood screws according to different nail heads. There are two types of slotted screws and cross recessed screws. Generally, the round head screws are made of mild steel and are blue, and the flat head screws are polished. The oval head screws are usually plated with cadmium and chrome, and are often used to install hinges, hooks and other hardware accessories. Specifications are determined by rod diameter, length and nail head type. [1]
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