What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
In order to solve the above-mentioned technical problems, the technical solution adopted by Guangdong Yueluo Hardware Industry Co., Ltd. is: shear rivets, including a mandrel and a deformation sleeve ring sleeved on the mandrel, one end of the deformation sleeve ring is a boss structure, and the It includes an adhesive collar sleeved on the deformation collar, the adhesive collar is a hollow annular sleeve and is filled with adhesive material; one end of the mandrel is a hemispherical head, and the spherical surface of the hemispherical head is outward, The connection between the hemispherical head and the mandrel is a conical connecting section, and the diameter of the conical connecting section gradually decreases from the hemispherical head inward; the mandrel is provided with a stress concentration groove, and the position of the stress concentration groove is close to the deformation The boss structure of the collar.
Yueluo relates to a self-tapping screw according to the preamble of claim 1. A self-tapping screw is known from EP0623759B1, the ratio of the outer diameter to the smaller diameter of the self-tapping screw is about 1.25-1.5, the ratio of the outer diameter to the pitch lead is about 1.5-1.6 and the thread The flank angles of , are < 50° and ≥ 35°. EP0433484B1 proposes a self-tapping screw whose thread is provided with cutting teeth of approximately arcuate design, and the cutting edge and the thread crest are at the same horizontal position and are set in opposite directions. One purpose of Yueluo is to realize a general type of self-tapping screw so that it can be screwed particularly easily into holes drilled in concrete or other materials such as bricks and the like. According to Yueluo, this object is achieved by the features in the characterizing part of claim 1, and surprisingly, it has been found that the parallel arrangement of the flanks, ie with a flank angle of about 0°, will make screwing particularly easy when screwing in , especially if the diameter of the hole varies within an allowable tolerance. One reason may be due to the fact that there is no lateral pressure on the material screwed into the thread, even if threads of different depths are cut in concrete or other materials such as brick, chipped plywood, or hardwood. The thread cuts into the material over its entire width by cutting grooves. In particular according to the embodiment of claim 3 the material cut out when screwing in the screw can be discharged without any accumulation, the dependent claims reflecting many advantages of further embodiments.
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 71 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.
When the tightening effect is achieved by the nut, it is often necessary to use a wrench to fix the nut or turn the nut to achieve the fixing effect. During the use process, the size of the nut is fixed, so it is necessary to use the corresponding type of wrench and the corresponding nut. In the tightening operation, during the installation process, the size of the wrench is large, that is, the nut cannot be manipulated, and it takes time to find a suitable wrench, which is inefficient.
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