Back in the SEVENTIES!
Mora, had a system of two blades on a single auger ( shaft ) ? Skipper should be right.
7" and 8" have the same hole spacing and shaft, 5" and 6", have the same holes and shaft, only in a smaller diameter! 5" and 4", might be a problem?
4" and believe it or not , 3", went together!
That's just a guess on my part?
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