plate 48 liftable by means of a compressed air cylinder 47 the right workpiece half 42 34 is clamped between the lower and upper clamping plates 46 48 both plates 38 44 are bridged by a rail 49 fig1 and 2 formed with an oblong hole 50 and displaceably secured by means of screws 51 to the plates 38 44 the rail is laterally guided in guide pieces 52 secured to the plates 38 44 by means of screws 53 disposed underneath the carrier bodies 10 and 12 are two master cam halves 54 and 55 fig1 and 3 arranged along the profile of which rolls a motor driven magnetic roller 56 which is located in the supporting arm 9 and the axis of which extends coaxially to the needle 57 of the sewing machine 8 both master cam halves 54 and 55 are connected by means of a bridging rail 58 fig1 along which the magnetic roller 56 rolls when shifting from one cam half to the other one disposed on the connecting girder 5 of the frame 1 is device 59 for properly inserting the workpiece the workpiece cuts 42 to be sewn into and sewn workpieces out of the clamping holders 38 39 42 the device 58 comprises.