Niagara Cutter N85908 Carbide Ball Nose End Mill, Weldon Shank, TiAlN Finish, Roughing and Finishing Cutting, 30-Degree Helix, 4 Flutes, 2.5" OAL, 0.250" Cut Diameter, 0.250" Shank Diameter NC tolerance end mills have a plus-tolerance cutting diameter to match those of high-speed steel end mills, allowing an upgrade from high-speed steel to carbide without changing diameter Four flutes produce a better finish than fewer flutes Titanium aluminum nitride (TiAlN) coating lubricates the end mill for high-temperature stability and abrasion resistance at high cutting speeds, offering better heat resistance than TiN and TiCN coatings Carbide can run at higher speeds than high-speed steel, resisting abrasion and high cutting temperatures Ball nose end mills (also called ball end) create contoured surfaces