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A 6 inch auger will be more than big enough. I've seen 36 inch pike come through 6 inch auger holes. Anything over 6 inches can be tough to drill by hand.
6" hole = 28.27433 sq. in. -- 8" hole = 50.26548 sq. in.
I also will opt for a sharp 8 over a dull 6, but that was not the question. As for having room for the transducer, just yank it out before you bring the fish to the hole. Drill a 50 hole grid with that 8 and tell me you're not tired.
You are saying that a quality 8 cuts better than a cheap 6. Come on, we all know that. A 61 years old guy was asking about ease of use / adequate size. You are introducing 2 variables into the question. 1=your high quality auger vs an unknown quality other brand. 2: your physical condition vs that of the OP. Sure your auger is fast. No argument there. You could use the same make and style in 6 inches and be almost twice as fast doing just over half the work per hole.
Please, guys. Let's not get into an argument. granted, Nils is a great auger. I know that you guys that own them can't say enough about them. out of my price range. also sharpening the blade is tricky (from what I have heard) also replacement blades are more expensive. when you guys talk about "Mora" is that the strikemaster Mora that you refer to? anyone ever have an exkimo hand auger?
6" nils. Best ice fishing purchase I've made.