Characteristics of end mills

Entering angle
The main feature of an end mill is that it has a entering angle of 90°. Larger diameter end mills can also be used as face mills with a 90° entering angle, so these end mills have some of the characteristics of the face mills discussed in Chapter 2. However, end mills often have a smaller diameter than face mills. In general, face mills are very rare under 20mm diameter, while 3mm diameter end mills are common for end mills.
Cutting edge
An end mill usually has two sets of cutting edges, one on the end face of the cutter and one on the circumference of the cutter. The cutter teeth located on the end face of the milling cutter are called "end teeth" or "end edges", while the cutter teeth located around the circumference of the milling cutter are called "circumferential teeth" or "circumferential edges", as shown in the figure.