With larger diameters than end mills, these cutters remove greater amounts of material to create a smooth, flat channel in the face of a plate, bar, or other wide workpiece. Compared to fly cutters, they’re more rigid, which makes for a better finish. Also known as shell cutters. Cutters with fewer teeth provide better chip clearance for high-volume, high-speed cuts. Those with more teeth provide a finer finish and generate less vibration at high speeds.

Cobalt steel cutters have better heat and wear resistance than high-speed steel. They can run at higher speeds and provide better performance on hard material such as iron, stainless steel, titanium, and tool steel.

Use uncoated cutters for general purpose milling and short production runs. They stay sharper than coated cutters when used on soft materials like aluminum. Use coated cutters for demanding, high-speed jobs in hard material as well as for longer production runs. The coating reduces friction and vibration as they’re used, making them more wear resistant than uncoated cutters.

Titanium-nitride (TiN) coated cutters create less friction than uncoated cutters, which means they last longer when run at similar speeds. Aluminum-titanium-nitride (AlTiN) coated cutters dissipate heat better than other cutters, especially at high speeds. At high temperatures, the coating creates a layer of aluminum oxide that transfers heat to the chips, keeping the tool cool, even when used without lubrication.