The end mill is one of the most commonly used milling cutters in CNC milling, and its structure is shown in the figure. There are cutting edges on the cylindrical surface and end face of the end mill. The cutting edge on the cylindrical surface is the main cutting edge, and the cutting blade on the end face is the secondary cutting edge. The main cutting edge is generally a helical tooth, which can increase the cutting stability and improve the machining accuracy. Since there is no cutting edge at the center of the end face of an ordinary end mill, the end mill cannot be fed axially, and the end face edge is mainly used to process the bottom plane perpendicular to the side.
In order to improve the chip curling situation, increase the chip space, and prevent the chips from clogging, the number of cutter teeth is relatively small, and the radius of the chip groove arc is relatively large. Generally, the number of teeth of a coarse-tooth end mill is Z=3 to 4, the number of teeth of a fine-tooth end mill is Z=5 to 8, the sleeve structure is Z=10 to 20, and the arc radius of the chip flute is r=2 to 5mm. When the diameter of the end mill is large, it can also be made into an unequal pitch structure to enhance the anti-vibration effect and make the cutting process stable.
The helix angle β of standard end mills is 40° to 45° (coarse teeth) and 30° to 35° (fine teeth), and the β of sleeve type end mills is 15° to 25°.
End mills with smaller diameters are generally made in the form of a shank. The end mills of φ2～φ71mm are straight shank; the end mills of φ6～φ63mm are Morse push shank; the end mills of φ25～80mm are 7:24 taper shank with screw holes, and the screw holes are used to tighten the tool . End mills with a diameter of φ40～φ160mm can be made into a sleeve structure.
