Those are quantom blades in that picture and they work great for reopening holes and I never had a problem with it being bad for the blades in fact that ring around the bit on the bottom is to help guide the blade when going through a preexisting hole
Mine looks like that. And it does reopen holes, and is sharp. But, had read in past it was not good for the blade. A friend indeed has attached a 10" Strikemaster, dual blade to his Eskimo so it does work. His impressively cuts holes quickly, at angles, etc. He spears so he does 5 holes side by side , 3 holes deep, then augers side ways to remove in between. Works well. Complete hole done, less scooping, in under 10 minutes.
Thanks for all the advice. Could use something larger than 8" anyway, so may go to 10. Also will redo back part by toy hauler door, under bunks to a 20" x 5' hole, covered and hinged of course. May spear, but even if not I love watching the fish and various movements of bait, etc.
Again, thanks for being generous.