I have had these for years. I had the early standard blades with the square tips, I think, and sent them somewhere and "they" ground them to a diamond/Vee point. (I'm a little vague on this, it's been a long time.) Later I loaned them to a fellow and he ground them down from the top and ground away all of the hardened metal. They were were worthless. Also, they were not properly curved when I got them and a friend and I rebent them and worked well until the guy ruined them. Mike hunter intervened and I sent the knives to him and he installed a diamond shaped cutter on each of them. This was a generous offer on his part. Either he did not charge me or charged me a nominal amount. The problem is the cutter is not wide enough. It may have worked better if they had install a square turned to present a point. The cutter needs to cut a kerf wider than the blade and it does not. I have battled my way through two cores and it was a fight.
I looked at buying new blades but a set of three looks' like it would be over $200. Somehow, this system has been cursed from day one and I am uncertain about spending several hundred dollars to resurrect it.
PS. I was wondering if the cutters were dull so I decided to reverse them to see if they work any better. I can't get the d@mn screws out. I have the little torx driver Mike sent me. Should I soak them with PB Blast or something?