PURPOSE: To improve the efficiency of many kinds of take-up work by blocking the optical path of a photoelectric sensor by a second arm to make the center of a core diameter coincide with the center of a core chuck.

CONSTITUTION: A first arm 3 is tilted by the contact with the outer diameter of a core fed to a vertically moving V-shape core bearer 1, and the inclination of a second arm 4 moved integrally with the first arm 3 makes the screening position of a photoelectric sensor 6 by the downward movement of the V-shape core bearer 1. This difference of the screening position makes the core chuck center of a full automatic take-up machine coincide automatically with the center of each core supplied to a core chuck even if the diameters of cores are diverse. The efficiency of many kinds of take-up work is thereby improved.