into which are inserted electrically insulated copper bars 14 14 a having appropriate cross sections the purpose of these bars will become apparent further below the connection between roll cores 4 stub axles 8 and jacket 12 is shown to better effect in fig4 where it is seen that cores 4 are connected to flanges 15 of stub axles 8 by means of screws 16 with the interposition of sealing washers 18 jacket 12 is seated on a shoulder 20 of flanges 15 and is sealed off by a sealing ring 22 further seen is an electromagnet 24 of which two are provided one on each side of rolls 2 see fig6 electromagnet 24 has a laminated c shaped core 26 and sloping pole faces 28 windings 30 are made of copper tubing each of the poles of core 26 faces a laminated annular armature 32 each armature being attached by means of screws 34 to flange 15 of the stub axle 8 of its roll 2 core 26 is slidably mounted on a bracket 35 fig1 which in turn is mounted on chassis 36 as the angle of slope of annular armatures 32 and the angle of slope of pole faces are identical gap a between rolls 2 which determines the thickness of the cast sheet can be altered without altering the air gap between armatures 32 and pole faces 28 by shifting core 26 in either direction of double arrow c windings 30 of electromagnet 24 are connected to a high frequency 2 5 10 khz source of a voltage 38 fig6 returning to fig1 there are seen coils 40 surrounding but not touching stub axles 8 each of coils.