sewing machine 2 is equipped with a thread cutting device of known design e g according to german pat no 1 125 742 due to the positioning motor 3 in conjunction with a synchronizer not shown disposed on the main shaft 1 it is possible to stop the sewing machine 2 at the end of a seam in needle down position then to initiate the thread cutting process with the main shaft 1 executing approximately one half revolution and at the end of the thread cutting process to stop the sewing machine 2 with the thread feeding lever tl up this position is chosen because in this position the thread feeding lever has completed the thread pull up and therefore exerts no pull on the thread in the following start up of sewing this deviates the possibility that the thread feeding lever pulls the thread end out of the eye of the needle to determine an additional stopping postion in the needle up position there is fastened onto an end of the main shaft 1 which extends out of the sewing machine housing a cam plate 12 which has a cam portion 13 with a radial shoulder 14 and at an angular distance therefrom an additional radial shoulder 15 cooperating with the radial shoulder 14 is a crowned driver cam 16 of a driving lever 17 which is guided for longitudinal displacement in a straightway guide 18 and is under the action of a compression spring 19 arranged in the guide 18 the guide 18 is machined in a housing 20 which also has a cylinder space 21 for a pneumatic piston 22 whose piston rod 23 is brought out through a bore in a sealing plug 24 the cylinder space 21 has on either side.