That's interesting and I appreciate the time you take to put into your remarks, but the ideas I was referring concerning the bench grinder, is best illustrated in a You Tube video.
Work Sharp 2000 Sharpener and Precision Grinder: Demo The part about hollow grinding with a bench grinder starts around 3:50. It's a little exaggerated when it come to the thickness of a lawn mower blade, but the principal is simular.
Anyway, thanks for your remarks.