Tony M Apr 8, 2023:

@ Asker Yes, it' a 6.3 mm drill bit (foret), and this is the size required to drive the 'core hole' to accommodate the central, 'solid' part of a screw, as distinct from the 'clearance hole', which the screw will pass freely without touching the threaded part.

florence metzger Apr 8, 2023:

foret à queue cylindrique diamètre 6,3