Hello

Files are like stones though using them is easier with odd angles that have to smoothed out to shape. That along with resetting the bore of the barrel with new rifling. The length and width of the file allow for precise finishing and smoothness. Stones are little bit harder to hold and are better clamped down. That makes it were the pressure may not be equal on application on to the surface of the part. Crossing, flat, barrette, half, and needle files are the most common metal use files. They are distinguished by their overall appearance. They are used for specific coarseness of cuts that are to be achieved when used. The shape of each one can vary from each other though the widths are the same. The different shapes allow for some ergonomics or even precise work to be done. The bastard file can be used on metal to make coarse cuts a little smoother if the area needs a second cut. While a smooth cut milling file can also be used on wood to achieve a smooth surface cut. From my experience growing up and using these files on parts for cars and on wood. Though I would recommend using sandpaper on wood after getting the desired cut to smooth it out. The same could be said with metal as well though it depends on the part whether or not it needs some sandpaper polish. That along with how often the part has to move and how much friction should be there as well.