1. Turning force test: The changing power of a product is its ability to resist being changed in half. Various standards stipulate the minimum requirements for the changing force of self-tapping screws. This test is to clamp the screw in a chuck with a tapping center split on the force-changing test tool, and then use a torque wrench to apply force until the screw breaks. If the torque does not exceed the minimum requirement of the regulations, the product will fail the test. Failure indicates that the screw is too soft or the main diameter of the thread is too small.
2. Locking test: This test is to lock the screw to a test plate, which has regular hardness, thickness and hole diameter. If the screw is locked through the test plate but the thread is deformed, the product is unqualified. Unsatisfactory results indicate that the surface hardening treatment of the screw is too shallow or too soft.
3. Locking torque test: This test is only required for screws with rolled screws. When performing the locking test, the minimum locking torque of the test plate is observed. If the torque exceeds the specified standard value (the standard value is based on the size and surface treatment of the screw), the product is unqualified. Failure indicates that the surface of the screw is not smooth enough, or the thread is improperly formed and requires greater torque.