of the cam 12 the feed arm 51 is made oblique by u03b5 1 in the clockwise direction around the pin 49d via the feed arm 17 the screw 34 the rod 36 and the feed arm 37 from the position where the pin 51c gives the feed amount 0 to the feed adjustor 57 and thus the required forward feed is obtained in fig1 the follower 17 the follows a convex portion of the cam 12 the feed arm 51 is made oblique by u03b5 2 in the counterclockwise direction around the pin 49d via the feed arm 17 the screw 34 the rod 36 and the feed arm 37 from the position where the pin 51c gives the feed amount 0 to the feed adjustor 57 and thus the required backward feed is obtained the above mentioned u03b5 1 and u03b5 2 may be made equal on design and therefore super stitching may be performed which is equal in the forward and the backward feed when the knob 3 is rotated from the condition in fig9 and 10 to the plus direction the feed control cam 47 is as shown in fig1 rotated in the clockwise direction via the shaft 44 since the feed adjusting arm 49 is rotated around the pin 6d.