Angular distributions of 42-MeV $\ensuremath{\alpha}$ particles, elastically scattered from $^{40,42,44,48}\mathrm{Ca}$, $^{46,48,50}\mathrm{Ti}$, $^{52}\mathrm{Cr}$, $^{54,56}\mathrm{Fe}$, $^{58,60,62}\mathrm{Ni}$ have been measured in the forward region with an absolute accuracy of \ifmmode\pm\else\textpm\fi{}0.1\ifmmode^\circ\else\textdegree\fi{}; in particular, the locations of the minima near 35\ifmmode^\circ\else\textdegree\fi{} (c.m. system) have been determined to within \ifmmode\pm\else\textpm\fi{}0.1\ifmmode^\circ\else\textdegree\fi{}. The theoretical analysis has been done in three ways, using (a) the Fraunhofer model, (b) a direct parametrization of the scattering amplitude in terms of three parameters, and (c) a standard four-parameter optical model. Strong-absorption radii have been deduced from the critical angular momenta extracted from the scattering amplitudes. In addition, attempts have been made to determine, for the optical-model analysis, other sorts of strong-absorption radii that are more characteristic of the scattering than the usual midpoint radius of the potential. Our analyses indicate that the rate of increase of almost all such strong-absorption radii is smaller within the Ca and Ti isotopes than within the Fe and Ni isotopes, the radius of $^{48}\mathrm{Ca}$ being anomalously small for all types of analysis.