Small-caliber high-pressure tapping machine and tapping method thereof

The invention discloses a small-caliber high-pressure tapping machine which comprises an outer sheath and a drill pipe; the outer sheath is formed by a fixed sleeve and a rotary sleeve, the rotary sleeve is formed by an inner wall and an outer wall, an external thread is formed on the outer surface of the inner wall of the rotary sleeve fixedly sleeving on the rear part of the drill pipe, an internal thread is formed on the inner wall of the fixed sleeve inserted between the inner wall and the outer wall of the rotary sleeve; a thrust bearing is fixedly sleeved at the tail part of the rotary sleeve, a bearing block of the thrust bearing is in sealed connection with the inner and outer walls of the rotary sleeve, a threaded pipe cap is screwed on the bearing block, and a ratchet wrench is arranged on the drill pipe extending out from a center hole of the threaded pipe cap; and a copper cover and a sealing cover sleeve on the drill pipe at the front end of the fixed sleeve, a vent valve is arranged in a through