The reason for the 1/64" part not sharpened is because if it is not then it will dull faster. So you will have to sharpen more often and over a shorter time frame replace the blades. I have tested this although not through scientific testing procedures and it is true. Sharp edge blades compared to 1/64" dull. I took all the yards and split them in half and changed blades for each half. Same 2 sets of blades all day. By the end of the day, the sharp blades were ripping the grass and dull edge blades were still cutting the grass. It added about an hour to all the mowing but it was an eye opener.