Tapping machine for screw machining and machining method thereof

The tapping machine comprises a workbench, a clamping assembly, a heat dissipation box and a frame body, a limiting barrel is arranged on the inner wall of the clamping assembly, a rack is installed on the inner wall of a limiting ring in a penetrating mode, and a positioning block is fixedly installed at one end of the rack; a plurality of sets of power supply assemblies are installed on the inner wall of the clamping assembly, and a plurality of sets of micro motors are installed on the inner wall of the clamping assembly. Screws of different sizes are rapidly fixed by installing the clamping assembly and the positioning block, when the tapping machine is used for machining and tapping the screws, the screws to be machined are placed in the limiting barrel, the output end of the micro motor rotates, the gear drives the rack to slide, and the screws can be clamped by the clamping assembly and the positioning block. When the rack moves, the positioning block is pushed to move, after the positioning block move