blade is then lowered into gripping contact with the chain and in readiness for the next seam to be sewn during this function the chain is stretched forwardly so as to enter the recess 33 located at the base of the tongue 13 and enters into the channel 29 thus placing said chain in alignment with the sewing axis and below the upper planar surface of the needle plate 11 the chain is caused to move in front of the needle and the loopers 12 and 14 to effect its entry into the recess 33 which locates said chain at a sufficient distance from the trimmer knife so as not to come into contact with it accidentally under these ideal conditions the seam may be picked up only if a new piece of material is moved into contact with the needle 10 the needle on its initial piercing of the material draws from its source of thread and restores the positions relative to the other stitching instrumentalities that are necessary for the required formation of the stitches because stitches at this point can only be formed when a piece of material is present there is no length of free stitches on the leading edge of the material to affect adversely the appearance of the finished seam in addition the pressure exerted by the workpiece on the work surface 15 and the needle plate 11 cannot displace the.