Abstract: The spin blast tool includes a housing having a tubular member rotatably disposed on bearings in the housing. A nozzle is mounted on one end of the tubular member and the other end of the tubular member is connected to a pressurized air and sand source. That end of the tubular member adjacent the presurized air and sand source includes a counterbore for receiving a tungsten carbide throat insert. The throat insert has an inner diameter which is smaller than the inner diameter of the tubular member. The insert has an annular radial flange juxtaposed with the end of the pressurized air and sand source. A polyurethane seal washer circumscribes the throat insert and is housed between the radial flange and the end of the tubular member. A wafer spring section is compressed between the outboard surface of the radial flange and the end of the pressurized air and sand conduit. The wafer spring section provides constant pressure on the throat insert as the throat insert wears.