weeks ago there were discussions on the need for hollow grinding. It had to digest this a while. In shop school I was taught that the reason for hollow grinding was to create 2 high points on the edge being sharpened. One cutting edge and a back edge just for angle reference. This was the days of chisel and plane irons. When ground with a hollow it is just shaping--not sharpening. When this blade is stroked on a flat stone only the metal on the cutting edge is removed. A bit on the back edge which merely keeps these 2 points in line. A consistent angle is easily maintained which is very condusive to a sharp edge. A blade can then be touched up on a stone many times between grindings. I got into the same procedure accidently when I rigged up some 6" diamond discs on a grinder. I still use my old wheels to shape (with a jig) and then hone on the flat discs of fine diamond grit. Almost no steel is removed by just barely touching the 2 high points to the diamond wheels and I go a long time between grindings. The dia. wheels are 6" lapidary discs by the way. Just rambling.
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