The taper mill are mainly used to repair the deformed fish top or trim the curling of the casing at the butt hoop of various tools and the burrs and flaring caused by perforation during the drilling process, and to clean up the mineral crystallization and other hard sundries trapped on the shaft wall, so as to restore the size.  Conical shoes are composed of conical body and YD alloy surfacing or insert welding hard alloy, as shown in the figure.  The taper of the cone is 30°, the cone is wing like, and the surface of the cone of the wing is welded with carbide.  The upper part of the shoe is a drill pipe thread, connected to the drill pipe, and the cylinder has a centering block to prevent severe milling of the casing wall during the operation.  There are 3-5 flume along the axial direction, and the body has straight-through or bypassing water holes from top to bottom to ensure smooth well cleaning. The taper mill are by the alloy on the cone milling protruding casing wall and stranded in the casing wall crystals and other impurities.  The cylinder section acts as a stabilizer, and the milling debris is carried back to the surface by the well cleaning fluid.