Shank Allows you to add an extra inch to the milling faces and loosen the shank 1 inch. Then it just fits in between the 16 center bolts (a standard heavy duty Milwaukee Hole Hog drill bit if you have a $300 90 degree drill bit). Why doesn't anyone do that in the 6" version? The short one is too small and clogs easily, this one is too long. A long shank isn't necessary. If you need more, you probably need a lot more and would still use a 10- Buy inch or longer version Also flutes can be sharper (Mo Betta stone mine now)