  Spinor fields with a vortex structure in free space that allow them to have
arbitrary integer orbital angular momentum along the direction of motion have
been studied for some time. Relatively new is the observation in a certain
context that the vortex center of this field structure is, unlike a classical
whirlpool, not singular. We point out that there are several ways to calculate
the local velocity of the spinor field and that all but one show a singular
vorticity at the vortex line. That one, using the Dirac bilinear current with
no derivatives, is the only one so far (to our knowledge) studied in the
literature in this context and we further show how to understand an apparent
conflict in the existing results.
