Milling cutters come in a variety of sizes, materials and configurations. The operation to be performed will generally determine the type of cutter to be used. High-speed steel (HSS) cutters have to be used at lower speeds and will not last as long as some other materials such as carbide. Carbide or cobalt cutters can produce work more quickly. The higher cost of these materials will need to be considered. The selection of the cutter will be affected by the size, shape and hardness of the part to be machined as well as the operation that needs to be performed.
A frequent operation on a vertical mill is cutting slots or keyways. With the proper feed, speed and coolant, a sharp end mill can cut a slot to within two one-thousandths of an inch. If great precision is required in the slot or keyway, an end mill slightly under-size can be used and then the part moved over with the mill table to make the finish cut. Climb-milling or moving against the rotation of the cutter can be used to make finish cuts depending upon the condition of the milling machine and depth of the cut.
Wide, shallow cuts can be made with fly cutters or slab mills.Face cutters can perform similar operations with replaceable carbide or ceramic inserts. Operations on gears can be performed with hob cutters or involute gear cutters. Hollow mill cutters can be used as alternatives to turning parts on a lathe. Contoured shapes can be machined using a ball-nosed end mill. Slot drills can cut straight down into a part and are designed to form keyways. Slots for woodruff keys can be cut using a woodruff cutter.
The design and shape of the cutter can affect the results. Larger cutters and more teeth allow faster material removal. Swarf removal is affected by the depth and angle of flutes.A greater number of flutes will allow faster feed rates. The helix angle will determine suitability to hard or soft materials. Extremely precise tolerances can be achieved with a single point cutter and light cuts. Better finishes can be achieved with finishing cutters that have a high rake angle.