This machine adopts two straight needles,vertical-axis ritating hook wit h self-lubricating feature for catching thread loops and sliding bar take-up to produce two lines of double lockstitch .The needle bar can supported by ball bearings.It is provided with syynchro tooth belt for driving,plunger plunger pump for lubricating,knob-type stitch regulator and lever type reverse feeding mechanism .A bobbin thread pullbac k spring in the bobbin case guarantees the accordance of needle thread and bobbin thread .Besides it features synchronized feeding of needle bar and feed dog .