An apparatus for removing the molding flash from normally soft or resilient molded parts, such as rubber, which utilizes a nonsymmetrical tumbling barrel for tumbling and mixing the parts to be deflashed. Low temperature fluid is fed into the barrel to cause freezing or embrittlement of the molded parts to a predetermined extent and temperature-responsive speed control is used for rotation of the tumbling barrel to achieve uniform results and improved efficiency in the cost and effectiveness of the deflashing operation. The temperature sensing probe is isolated from the parts being tumbled, but is so located as to more accurately reflect the temperature of the parts, rather than the temperature of the atmosphere in the barrel. The electric motor utilized to drive the tumbling barrel is disposed in the path of exhaust flow of the cryogenic gas so as to be cooled thereby to reduce the heat factor and consequently the power requirements.