5 and their pitch is so selected that it corresponds to the desired pitch of the helices 1 1 39 for each helix 1 1 39 an upper conveyor spindle 24 and a lower conveyor spindle 24 39 are provided which grasp the helices 1 1 39 between them the helices are withdrawn from the heating chamber 5 through the cooling means 6 and through the shunt 7 by the draw off rolls 8 8 39 for smooth operation of the apparatus it is important that a predetermined pitch is precisely imparted to the helices 1 1 39 preferably the helices 1 1 39 are also advanced through the cooling means 6 by way of conveyor screws or spindles suitably the conveyor screws or spindles 24 24 39 extend from the entrance into the heating chamber 5 to the exit from the cooling means 6 so that the helices 1 1 39 are advanced by one conveyor spindle 24 24 39 through the heating chamber 5 and the cooling means 6 fig1 is a plan view of a conveyor spindle 24 the conveyor screw or spindle 24 has a diameter of 46 mm and 15 turns for example it is installed in a heat treating chamber comprising a heating zone 25 and a cooling zone 26 the direction of advance in fig1 is from left to right and is indicated by arrows from fig1 it is.