  Naively, helicity flip amplitudes for fermions seem to vanish in the chiral
limit of light-front QCD, which would make it nearly impossible to generate a
small pion mass in this framework. Using a simple model, it is illustrated how
a large helicity flip amplitude is generated dynamically by summing over an
infinite number of Fock space components. While the kinetic mass is basically
generated by a zero-mode induced counter-term, the vertex mass is generated
dynamically by infinitesimally small, but nonzero, momenta. Implications for
the renormalization of light-front Hamiltonians for fermions are discussed.
