Depends on how you cut them. If you use a pipe cutter it gives smooth edges. But if like most of us you cut it with a hacksaw you get a ragged edge. Take a sharp knife and run it around the outside to trim the strings. Then do the same to the inside called reaming. If this is not smooth enough for you run some sandpaper around the inside and inside. If the cut is not square enough for you put a piece of sandpaper on a flat surface and scrub the end of the pipe over it until flat. Start with fairly course paper to remove the most materia until flat. Use progresseively finer grades until you get the smoothness you want.