a breather port 126 for the venting necessary to relieve the residual pressure urging the abrasive material 44 into the hopper compartment 42 the abrasive dispenser will thereby be at ambient pressure and be released through the non occluded portion of the metering orifice 54 sufficiently by gravity in certain alternate embodiments drive shaft 76 acts both as an aspiration conduit as well as a torque communicating member between the motor 78 and shutter assembly 74 it concurrently serves as the aspiration conduit through which the high speed air jet 58 is directed as shown in fig9 the drive shaft is formed in this embodiment as a hollow lightweight drive tube 76 u2032 the drive tube 76 u2032 then defines an axial bore which serves sufficiently to conduct the high speed air jet 58 induced during operation to minimize destabilizing inertial effects this drive tube 76 is preferably formed of a material of any suitable type known in the art having minimal weight yet sufficient strength and durability to effectively withstand the torsional forces to be encountered in the intended application while not shown for clarity a guide shaft tube 94 is preferably disposed coaxially about the drive shaft tube 76 u2032 much as it is in the embodiment described in preceding paragraphs the guide shaft tube 94 accordingly.