What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
In view of this, a screw with waterproof, anti-loosening and anti-removal functions is provided. A screw comprises a screw rod and a screw head connected with the screw rod, the diameter of the screw head is larger than the diameter of the screw rod, and an annular groove is formed around the screw rod on the surface of the screw head connected with the screw rod, The screw head is also provided with a through hole penetrating the screw head, and the through hole is communicated with the annular groove for filling the annular groove with adhesive substances. Compared with the prior art, the screw provided by Guangdong Yueluo Hardware Industry Co., Ltd. has a structure in which a through hole and an annular groove are arranged on the screw head, so that after the screw is locked into the screw hole, the screw head is not locked. A glue storage flow channel is formed between the contact surface with the part, and then the glue material is injected into the glue storage flow channel through the through hole to form a sealing annular rubber ring, so as to better ensure the waterproof performance of the screw joint. Furthermore, by connecting the through hole with the screwdriver groove, while forming a sealing annular rubber ring, the driver groove can be directly filled for the purpose of preventing dismantling.
In the prior art, spring pads are fixed to the seat pan or to the height adjuster tube. However, in the absence of a seat pan, additional components are required to secure the spring pads to prevent movement of the spring pads in the longitudinal direction of the vehicle. FIG. 1 shows such a seat spring pad 2 , which is fixed to the seat pad 1 by means of additional fixing parts 4 . Additional weight is added due to the use of additional fixing parts and a separate step is required in the assembly process to connect the fixing parts to the spring pads. During use, there may be noise between the spring cushion and the seat cushion
With the rapid development of electronic technology, the integration of circuit boards is getting higher and higher, and the number of layers of circuit boards is increasing. Press-fit and fix to ensure accurate alignment during riveting and pressing. The rivets used on PCB boards are basically brass rivets. When riveting and pressing multi-layer PCB boards, metal chips are prone to appear, inner layer short circuits or foreign objects between layers, and because of the brass rivets With higher hardness and larger wall thickness, the riveted area of the PCB is thicker than the non-riveted area, which is easy to cause damage to the middle steel plate of the auxiliary tool. At the same time, the protruding rivets hinder the free expansion of the copper foil, which is easy to produce copper foil. wrinkling phenomenon. Now there are improved plastic rivets used to manufacture multi-layer PCB boards. The advantage is that no metal debris is generated, and at the same time, the tool steel plate is not damaged to the greatest extent. However, the existing plastic rivets are insufficient due to the inherent strength of plastics. When the PCB board is riveted and pressed, it is easy to deform, and the positioning is inaccurate, resulting in dislocation between layers, resulting in poor improvement of the product defect rate.
The lifting ring screw should be made of 20 or 25 steel (GB699). The lifting ring screw must be forged as a whole. The forgings should be normalized and the oxide scale should be removed. The grain size of the finished product should not be lower than grade 5 (YB27-77). There must be over-burning, crack defects.
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