Abstract: Sheet Metal thermal control dampers are disposed in the cavities between turbine blades to bear against the undersides of opposed blade platforms portions of angularly adjacent blades under centrifugal loading to dampen blade vibrations and to seal the gaps between platforms against the radial flow of working fluid into the interblade cavities. The dampers are configured to cooperate with forward and aft seals to also block the axial flow of working fluid through the interblade cavities. Holes are provided in the dampers through which cooling air introduced into the interblade cavities can flow into contact with the platform undersides and cool the platforms, thereby controlling temperature rise in the blade attachment structure.