Bolt detection divided into manual and machine types. Manual is the most originaland most common use of the same detection. In order to minimize the outflow ofdefective products, general production staff through a visual approach to packaging or delivery of the products tested to rule out defective (bad including tooth injury, blending, rust, etc).

Another way to machine-automatic testing primarily magnetic particle inspection.Magnetic powder testing is using bolt defects at of leak magnetic field and magnetic powder of mutual role, for bolt may exists of defects (as crack, clip slag, mixed material,) permeability and steel permeability of differences, magnetization Hou these material not continuous at of magnetic field will occurred Qi variable, formed part magnetic pass leak at artifacts surface produced has leak magnetic field, to attract magnetic powder formed defects at of magnetic powder stacked--magnetic marks, in appropriate of light conditions Xia, appeared out defects location and shape, on these magnetic powder of stacked be observation and explained, Achieve the objective of eliminating defective products.