The pure shear strength for the all-simply supported plate has not yet been found; what is described as pure shear in that plate, is, in fact, a pure-shear solution for another plate clamped on the "Y-Y" and simply supported on the long side, X-X. A new solution for the simply supported case is presented here and is found to be only 60-percent of the currently believed results. Comparative results are presented for the all-clamped plate which exhibits great accuracy. The von Misses yield relation is adopted and through incremental deflection-rating the effective shear curvature is targeted in aspect-ratios. For a set of boundary conditions the Kirchhoff's plate capacity is finite and invariant for bending, buckling in axial and pure-shear and in vibration.