Page "learned" Paragraph 1291

In the first picture ( 9a ) the knife is just beginning to advance into the inclined surface which was left from the previous chip formation.

In the next, the shear plane angle is high, and extends to the inclined work surface.

With increasing advance of the knife into the coating the shear plane extends to the coatings surface and the shear angle rapidly decreases.

Eventually, rupture occurs along the shear plane ( 9e ), and the cycle repeats itself.