Such machinery have adopted the connecting bar thread-taking-up, large rotating hook thread-hooking, needle bar swing, drop feed to form the 301 and 304 lockstitches. Their outline are beautiful. The sewing speed is high. The adoption of double-large rotation hooks greatly improves the working efficiency. The adoption of the rotating hook shaft directly-driven by the lower shaft eliminates the transition gears, simplifies the structure and reduces the clearance of the thread-hooking mechanism. The full-automatic lubrication system reduces the operation noise and extends the service life. They are applicable to the straight sewing, zigzag sewing and joint sewing of medium-thick, thick materials and are widely used for the sewing of garments, cases, leather, footwear and headwear.