If you try to cut deeper than the area with cutting flutes, the shank of the tool will rub on the side wall, so you won't get any cutting action. If you can't live with a slight step in your pocket, then get a tool with a longer cutting length. The only exception would be in the case of a tool with a fluted area larger in diameter than the shank of the tool. It would be able to cut deeper, but there aren't many end-mills like that.
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