Abstract: A machine for conveying and blast treating workpieces by an abrasive or blasting medium includes at least one rotatable barrel or drum in a blasting chamber, the axis of rotation of the drum being inclined downwardly in the direction of conveyance. The diameter of the drum decreases in the direction of conveyance and a blast wheel is mounted at the upper, larger, input end of the drum. The lowest generatrix of the drum is horizontal or slightly inclined upwardly in the downstream direction. In a preferred embodiment, the drum diameter decreases in stepwise fashion. Axially extending impeller members in the drum provide for uniform travel of the workpieces. In one embodiment, a discharge drum and a housing drum are rotatable with the blasting drum.