Ballnose

A ballnose, also called a ball-end mill, is a milling cutter with a hemispherical tip that forms rounded surfaces and complex three-dimensional shapes. Ballnose cutters are commonly made from carbide or high-speed steel and may be coated with wear-resistant layers such as TiN, TiAlN, or AlTiN. They are manufactured in a wide range of diameters, from fractions of a millimeter to several millimeters or more, with two, three, or four flutes and helix angles typically between 30 and 45 degrees. The tool radius determines the curvature produced in the workpiece.

The defining feature is the hemispherical tip; the radius of the cut equals half the tool diameter. This geometry makes ballnose mills well suited for 3D contouring and finishing of curved surfaces, but less efficient for sharp corners or pockets with acute radii. Surface finish depends on step-over, step-down, feed rate, spindle speed, tool diameter, and whether climb or conventional milling is used. Smaller-diameter tools provide finer detail but wear faster; larger tools remove material more rapidly but create larger scallops if the path steps are not sufficiently small.

Applications include sculpting and finishing complex surfaces in wood, plastics, and metals, as well as mold making and relief carving. In CAM workflows, ballnose milling is paired with toolpaths designed for 3D surfaces, such as parallel, offset, or Z-level passes, to create smooth, continuous curvature.

Selection and use: choose a diameter that matches the desired curvature, select an appropriate coating for wear resistance, and set feeds, speeds, and step-over to achieve the target finish. Proper clamping and cooling/lubrication are recommended to extend tool life.