A bearing unit comprising a stationary radially outer ring with a spherical radially outer surface with a convex shape, a radially inner ring that is rotary about a central rotation axis (X) of the bearing unit and is mounted on a rotating or oscillating shaft. A diametrical through-hole is formed in a first cylindrical portion that is used to receive an elastic element for locking the radially inner ring on the shaft, a plurality of rolling bodies interposed between the radially outer ring and the radially inner ring to enable the relative rotation of the two rings, and a locking element locking the radially inner ring on the shaft. The radially inner ring is provided with two threaded through-holes from opposite sides with respect to the radially outer ring and to the rolling bodies, for housing respective grub screws for locking the radially inner ring on the shaft.