Flywheel skimming in the lathe
Skimming the flywheel in the lathe allows you to get under and remove the work hardened spots caused by heat when slipping the clutch. These spots can be seen on the machined surface that I am cutting they on this pass, they look like little polished blemishes roughly the size of a small button.
These hardened spots will wear slower than the surrounding surface and damage your clutch disc.
I have found that the workshops that offer a stone ground job (Blanchard Grinding) do not always get in under those hardened spots and can thus cause premature wear of your clutch.