Abstract: A thread tension control system for a sewing machine comprises the following elements arranged in sequence in a path of thread travel extending between the thread supply and needle of a sewing machine, an infinitely variable thread tension control device; a tortuous path thread tension control device; a check spring; and a take-up arm. The tortuous path thread tension control device comprises a generally cylindrical thread tension control post for receiving at least one wrap of thread, the thread tension control post being disposed approximately orthogonal to the path of thread travel. The tension control post is disposed in the path of thread travel between the infinitely variable thread tension control device and in the check spring to effectively multiply the tension provided by the infinitely variable thread tension control device and insulate the same from changes in pressure along the stitch line.