Solid carbide end mills
Solid carbide end mills are a major component of carbide cutters (the other main component is carbide die milling cutters, which will be discussed in Chapter 5 of this book). The main part of the solid carbide end mill is shown in Figure 3-8. The solid carbide milling cutter is mainly divided into two parts: the working part and the shank. At present, the commonly used diameter range is 3~20mm. Milling cutters smaller than 3mm or larger than 20mm are also available, but they are not widely used and are not mainly discussed in this book.
3-8
The working part of a solid carbide milling cutter
The working part of the cutter is roughly composed of three cutting edge segments: the end teeth, the circumferential teeth, and the tip radius or chamfer that transitions between the two.
End teeth
The end teeth of the end mill are those parts of the teeth that are perpendicular to the tool axis at the head of the milling cutter. The main parameters of solid carbide end mill end teeth are shown in Figure 3-9. There are two main types of milling cutter end teeth, one kind of cutter tooth is longer, which will cross the axis of the milling cutter, and this cutter tooth is called the over-center cutter tooth; The other is a shorter tooth that does not cross the cutter axis. In Figure 3-10, the red size of the figure below is the long tooth (over the center tooth), while the blue size is the short tooth (but the center tooth).
3-9
Front and rear corners
Like all tools, carbide end mills have a rake and a relief angle. When the end teeth are inserted into milling (also referred to as "drilling") at a downward feed (see the right feed in Figure 3-11), the end teeth are the main cutting edge that undertakes the main machining task. Analyzed as a sharp point on one of the cutting edges (blue dot in the figure), the direction of the cutting speed is shown by the blue arrow when the feed rate is ignored. The cutting plane for this point is shown as a thicker red dot line in Figure 3-11, while the cutting plane is a thicker green line in the figure. Based on these planes, the rake and back angles of the end teeth can be obtained. Because the end mill end edge needs to contain more chips in a smaller space, it is often necessary to remove more material at the back of the end tooth to create a second relief angle of the end tooth. The second posterior angle is the darker yellow part of Figure 3-10.
3-10
3-11
End backlash angle
The end teeth of the end mill have a special angle, which is called the end backlash angle in Figure 3-11. This gap angle is more prominent in the outer circle of the end edge of the cutter than at the paraxial axis, and the teeth on the end face of the cutter form a concave "disc" shape, so this end backlash angle is also called the "disc core angle". The backlash angle at this end is generally about 2°.
Figure 3-12 is a schematic circle about the effect of the backlash angle at the end. When the milling cutter is axial feeded, the end edge is used as the main cutting edge, and the end backlash angle plus 90° is the entering angle of the end teeth: and when the milling cutter is radially fed, the circumferential edge becomes the main cutting edge, the end edge becomes the secondary cutting edge, and the backlash angle of the circumferential tooth is the secondary entering angle.
3-12
End tooth groove
For end mills with over-center cutting edges, there is also a structure on the end teeth: the end tooth groove. In Figure 3-13, the red circle is the end tooth groove.
3-13
