A heat brake for heating and softening a thermoplastic sheet for bending is disclosed. The heat brake has a split work piece support table having two edges defining a slot between adjacent portions of the table. A first plenum is provided below the split work support table. During operation, the first plenum has a negative pressure. Air is drawn into the first plenum through the slot when a work piece does not span the slot. When a work piece spans the slot, the flow of air into the first plenum is reduced. The heat brake has a tube heater with an outlet nozzle positioned in the first plenum. A portion of the tube heater is positioned in a second plenum which is pressurized during heating. Air is moved from the second plenum through the heater tube and is directed against a work piece supported on the table.