A
sewing machine comprising: a base defining a
support plane for at least one piece of fabric to be sewn; a needle designed to move through the fabric to be sewn with a
reciprocating motion comprising a forward
stroke to insert a main thread through the fabric to be sewn and a return
stroke to enable the main thread to form a loop below the fabric to be sewn; a feeding device of a secondary thread designed to provide an intermittent feed and to insert a
coupling portion of the secondary thread through the loop of the main thread; a
cutting device for separating the
coupling portion from the secondary thread; wherein the feeding device of the secondary thread comprises two rollers with parallel axes and provided with side surfaces facing each other and between which the secondary thread is tangentially fed; wherein, at least at the secondary thread, the distance between the side surfaces of the rollers is cyclically variable between a first distance less than a
diameter of the secondary thread, where the secondary thread is flattened between the rollers, and a second distance greater than the
diameter of the secondary thread, where there is clearance between the secondary thread and the rollers.