FIELD: machine engineering, metallurgical industry branches, namely manufacture and exploitation of heavy rolling mills. SUBSTANCE: apparatus is mounted in lower end of nut and on safety cone recess of screw and it is in the form of rings with wedge-shaped stops. Use of said stops provides jamming effort of screw when limit switch of motor of screwdown mechanism is not operated and rolling roll is raised upwards at level higher than admissible one. Said jamming effort is several times less than releasing force created by motors. Attachment for periodically measuring wear of turns of screw-nut pair is also mounted on said stops. EFFECT: simplified design, enhanced reliability of apparatus. 6 dwg
