Abstract: An improved system for generating an abrasive fluid jet is shown and described. In a preferred embodiment, abrasive is fed from a bulk hopper into an air isolator having a baffle that limits the flow of air and abrasive through the air isolator, thereby venting air from the abrasive. An on/off device having a rod coupled to a stopper is provided within the air isolator, the rod being selectively raised and lowered in a vertical direction. A discharge orifice is provided in a bottom surface of the air isolator, the stopper covering the discharge orifice when the rod is in a lowered position, thereby preventing the discharge of abrasive from the air isolator.A metering disk is provided adjacent the discharge orifice, an orifice in the metering disk being aligned with the discharge orifice, such that abrasive exiting the air isolator flows through the metering disk.