Such machinery have adopted the connecting bar thread-taking-up mechanism, the rotating hook thread-hooking mechanism and the connecting bar feeding mechanism. Compared with ordinary lockstitch sewing machinery, such machinery have been equipped with the advanced computer-control system and their maximum speed can reach 5000 R.P.M. They can function in automatic needle stopping, automatic thread cutting, automatic thread-wiping, automatic needle positioning, automatic stitch-set sewing and automatic bartacking. The low-tension design on the thread-passing parts can ensure that no wrinkle will happen when thin materials are sewn. Due to their reliable and stable thread cutting operation, such machinery can meet requirements on cutting of threads of different kinds and different diameters. Such machinery are particularly applicable to short-seam processes, like the sewing of brands, pockets and cuffs, to realize a perfect sewing effect. They have been applied for the national patent.