First, visually inspect: Check if the screw head is missing or separated from the shank. If the screw head is missing, leaving only a hole or remnant, or if the head was found to have detached during disassembly, it can generally be determined that it is completely broken. For fractures within the hole, use a magnifying glass or endoscope to observe the fracture surface.
Second, try applying slight torque: Gently rotate the screw with a matching screwdriver. If there is no resistance, it spins freely, and the screw shows no signs of moving up or down, it indicates that the shank has lost connection with the head, and it is likely completely broken.
Furthermore, verify the connection function: If the screw is responsible for fastening two parts, and the connected parts are noticeably loose, displaced, or cannot be tightened, even if the head has not detached, internal fracture may have caused functional failure.
Finally, use auxiliary methods for confirmation: Apply lubricant and wait a moment before trying to remove it; if it still cannot engage or withstand force, combined with any unusual feel during previous installation (such as a sudden "click"), this further confirms that it is completely broken.
