Abstract: Apparatus for the rapid removal of burrs from workpieces by the application of transient thermal energy in a closed chamber. The chamber comprises a downwardly open upper closure fixedly supported above a vertically movable lower closure, both closures being water-cooled. Means are provided for alternately moving work supporting platens into position above the retracted lower closure. After being raised by a yieldable motor, the lower closure is drawn into sealing contact with the upper closure by a plurality of screws mounted around the upper closure and supporting a clamping ring. Pressure tightness is achieved by an uncompensated seal which does not require excessive clamping forces. Combustible gases are metered to the chamber and at the same time to charging cylinders, the gases in the charged cylinders then being forced into the chamber to obtain the maximum gas charge.