What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
When the mold is manufactured, many positioning pins need to be installed to fix the relative position between the two parts. The positioning pins are usually sunk into the positioning pin holes on the mold. Since the mold needs to be pulled out frequently during assembly, in order to Remove the parts and make corrections. At the same time, the mold also needs to pull out the positioning pins during maintenance to remove the damaged parts for maintenance. Therefore, the workload of pulling the pins is large. The existing methods are: 1) When installing the pins, The operator uses a self-made long screw that matches the threaded hole of the pin to screw it into the pin, and then aligns the pin hole with a hammer to hit the screw to make the pin snap in, and then screw the screw out by hand. The disadvantage is: on the one hand, the hammer hits the screw It is easy to cause the screw to be damaged or deformed, and it cannot be used normally. On the other hand, it is labor-intensive to remove the screw by hand and may not be able to be removed; 2) When pulling out the pin, the operator will screw the screw into the pin and use force directly or with pliers To pull out a screw, a few companies use a large pin puller to pull it out. The disadvantage is that it is too laborious and time-consuming to pull out by hand or with pliers. Even if a large pin puller is used, the weight of the pin puller itself is large. , it is inconvenient to use.
The conventional auger bit structure 1 includes a rod body 11, a screw head 12 provided on one end of the rod body 11, a drill tail 13 provided on the other end of the rod body 11, and a plurality of threads 14 arranged around the rod body 11; Wherein, the periphery of the drill tail 13 defines a parting line 15, and the parting line 15 makes the drill tail 13 symmetrically divided into a side 131 and a side 132, and a cutting end 133 is formed at the junction of the end of the side 131 and the end of the side 132, respectively. The cutting end 133 is concavely provided with a quarter-turn chip flute 134 in the same direction of the helix, and the edge 132 continues the chip flute 134 and has a quarter-turn chip flute 135 with different helical curvatures. , by connecting the chip groove 134 and the chip groove 135 through different helical curvatures, the drill tail 13 can form a symmetrical and complete chip groove of 188 degrees.
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 4 the material cut out when screwing in the screw can be discharged without any accumulation, the dependent claims reflecting many advantages of further embodiments.
Nuts cooperate with screws to achieve the fixing and connection of components. SMD nuts are generally used in the circuit board industry to fix electronic components. That is, the chip nut is soldered on the circuit board by solder, and the electronic components are fixed by turning the screw. However, when the current chip nut is soldered on the circuit board, there may be uneven soldering, which makes the soldering untidy. At the same time, during soldering, the excess solder overflows from the periphery of the nut, which affects the appearance and may affect its appearance. electrical properties. In addition, the nut is only welded with the circuit board on one end face, and its firmness and reliability after welding are low.
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