This work concerns analysis of spherical indentation experiments throughextensive finite element simulations involving the J2 flow and the J2 deformationplasticity theories both under finite and infinite deformationsto gain a fundamental comprehension into the mechanics of the transitionbetween elasto-plastic and fully-plastic contacts. A decrease in hardnesswith increasing penetration is found to be a manifestation of the differencesin material pileup responses between the two plasticity theories, so that incontrast to prior investigations, a peak in hardness cannot be taken to markonset of a so-called finite deformation fully-plastic regime. The accuracy ofTabor’s hardness relation is examined in detail in light of the simulationsand a general relation is proposed through dimensional analysis to correlatehardness with the uniaxial mechanical properties for any arbitraryelasto-plastic or fully-plastic contact. Experiments are also performed indifferent groups of metallic materials and a methodology is proposed to extractyield strength ys and power-law strain hardening parameter n froma minimum of two hardness measurements performed at different penetrationdepths. Influence of pressure sensitivity in the extracted properties isthen examined through the experimental results. The issue of the uniquenessin the extracted properties and of frictional effects between indenterand material are briefly covered. The investigation ends with a discussionon the robustness of mechanical property extractions through singlecrystal spherical indentation experiments. Along these lines, consistency isfound between simulations with the flow theory of plasticity and the crystalplasticity model for fcc metals. Finally, the potential of spherical indentationto distinguish between single crystal elastic and plastic anisotropy isconsidered.