The shot velocity in two pneumatic shot-peening machines has been examined by means of experiment and theory. The shot velocity was measured under various operating conditions by a high-speed shutter TV camera. As a result, the shot velocity over the usual range of shot diameter D, shot density p, and air-pressure p was related by the formula, V=K·Dα·ρβ·(p+pb)γ, where Pb is atmospheric pressure. α and β are almost independent of the shot-peening machine, and α ≈ 0.36, β ≈ 0.48, K and γ are dependent on the shot-peening machine. On the other hand, the theoretical consideration based on hydrodynamics tied to the derivation of the formula, V=K·D-0.44·ρ-0.44·(p+pb)0.43 for the suction type machine, and almost the same formula for the direct-pressure type. The theoretically derived formula coincided well with the experimentally induced formula.
