What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
There are two typical pin shearing fixture tooling, among which the traditional fixture shown in Fig. 1 is more complicated and consists of fixture, spacer, washer and shearing block guide post, hardened bushing, shearing block and so on. The cylindrical pin is installed in the hardened bushing, and the axial load is applied through the shear block to complete the shear test. The fixture is complicated in manufacture and has many consumables, because the size of the hardened bushing is similar to that of the cylindrical pin. , and to keep the notch of the cylindrical pin upward, it is difficult to install before the test, and the broken cylindrical pin after the test remains in the hardened bushing and is difficult to remove.
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.
Convex washers are mainly punched out of iron plates. The shape is generally a flat washer with a hole in the middle. Flat washers are usually thin pieces of various shapes to reduce friction, prevent leakage, isolate, prevent loosening or Dispersing pressure, the rationality of its design structure and the safety during use are very important.
Currently, a screw generally includes a shank body, a threaded portion formed on the outer edge of the shank body, and a conical head formed at the rear end of the shank body. When the current thread is in use, since the thread part is cylindrical, the thread part and the workpiece are vertical, so it is relatively laborious when in use, and it is difficult to locate, lock and unlock.
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