Motoman here. The original blade on my craftsman DYT 4000 48" had 3 "hollow ground blades Yes, like the straight razor. When you sharpen the blades a couple times the hollow is gone and you are faced with the same task as in sharpening chisels,knives, drill tips , etc. How to obtain an edge that is sharp ,but that will last.
The blades are thick .080" ? The problem is as you proceed the thickness is an obstacle to a sharp blade and I alway take down about up to 1/8" of thickness behind the final, desiired cutting edge. This is sometimes referred to as the secondary bevel. The final edge is tapered down from the thinned bevel behind it. I do this on a hand grinder with a lowly grey wheel. But the technique is not acquired overnight. I make one or two uninterrupted passes for the secondary with fairly heavy pressure against the wheel and stop. Then tilt the blade infward to put the primary cutting edge on.
The blades are thick .080" ? The problem is as you proceed the thickness is an obstacle to a sharp blade and I alway take down about up to 1/8" of thickness behind the final, desiired cutting edge. This is sometimes referred to as the secondary bevel. The final edge is tapered down from the thinned bevel behind it. I do this on a hand grinder with a lowly grey wheel. But the technique is not acquired overnight. I make one or two uninterrupted passes for the secondary with fairly heavy pressure against the wheel and stop. Then tilt the blade infward to put the primary cutting edge on.