Lathe duplicators are an essential piece to make replicating spindles and other pieces on your lathe. The function of a duplicator is rather simple in theory, there is a stylus that passes over the piece to be replicated and a cutter attached to the stylus. Thus when the stylus moves with the contours of the piece the cutter moves as well. This produces an exact replica of the table leg or whatever item you are duplicating. By replacing the cutter when it is dull you can help prevent imperfect replicas and help the unit make smooth, clean cuts.