This chapter discusses interconversion phenomena between spin and mechanical angular momtum. In moving objects, the spin gauge fields emerge from inertial effects and produce angular momentum transfer between mechanical motion and spin. Such spin-mechanial effects are predicted by quantum theory in non-inertial frames, and confirmed by recent experiments including the resonance frequency shift in NMR, the stray field measurement of rotating metals, and the inverse spin Hall voltage generation in liquied metals. These spin-mechanical effects that arise via the spin-gauge fields open a new field of spintornics, where spin and mechanical motion couple harmoniously.