With blades pointing front to back ,the back edge should be 3 1/4 " off the ground,the front should be 3 ' off the ground with the deck in the lowest setting. If the star is worn off on the shaft it will let the blade lean to one side or the other thus making it not cut level. make sure your blades are not rounded on the edges ,if they are replace them...I know craftsman mowers just about as well as sears as i have sold them along with poulan which is the same mower..If i can help call me 423-586-6071..Thanks Bill