Thermal Heat Flattening and Ovality Correction are processes where parts are subjected to pressure during a stress relieving or temper operation for the purpose of improving the overall flatness and ovality of ring shaped parts. Parts can be flattened up to .250″ within a tolerance of .008″.
This is a process that we here at Modern Heat Treating perform often.
In the first photo you can see how the rings, when stacked, do not lay flat. You can see the gaps between them quite easily.