As the relative sizes of the feed, depth of cut and tool nose radius change, the shape of the uncut chip cross-section changes. Figure 6.15 shows four examples for the turning process, with which many engineers and certainly all tool engineers are familiar, but which could represent any process, as discussed in Chapter 2. The hatched areas are the uncut chip areas projected onto a plane normal to the cutting velocity. The directions and size of the feed and depth of cut are marked. Points such as 1 and 2 lie on the major cutting edge; and 3 and 4 on the tool nose radius or the minor cutting edge. Figure 6.15(a) is a case in which both the feed and depth of cut are large compared with the tool’s nose radius; in Figure 6.15(b), the feed is becoming small compared with the nose radius, but the depth of cut remains large; in Figure 6.15(c), the depth of cut is reducing; and in Figure 6.15(d), machining is confined entirely to the nose radius region. The different cross-section shapes in these cases lead to different detail in estimating the shear plane and other areas. The further detail in the figures is concerned with this and is returned to later.