Mechanical properties of screws

When using screws, simply tightening them is not enough. In order to connect two items to each other, screws that meet their conditions should be used and tightened accurately. In addition to size, mechanical properties need to be considered when selecting screws.
 Mechanical properties: The method of placing the screw into a universal material testing instrument and the method of cutting off the test piece before doing the experiment if the screw itself is too thick. A simple test method is screw hardness measurement. However, because the screw head and tip of the cold pressed product are hardened after processing, it is necessary to cut the shaft and measure its cross section.
The inspection of self-tapping screws is to install the screws on a test plate that meets the specified hardness, plate thickness, and inner diameter, and measure the torque of the protruding part of the screw on the opposite side. Clamp the tip of the screw and measure the torque until the screw is cut off. Self-tapping screws do not need to consider the location of the opposite hole, so they are widely used. When the corresponding steel plate is thin, repair processing is performed on the plate to increase the actual plate thickness. The selection of the relative lower hole diameter is very delicate from the perspective of operating performance. When used for synthetic resin, change the pitch, thread angle, and mountain shape.