If a gear with case-hardened teeth shows individual indications on five teeth, what is the probable identity of these indications?

The presence of individual indications on the teeth of a gear with case-hardened properties strongly suggests the presence of grinding cracks. Grinding cracks are typically shallow surface defects that can occur due to the thermal and mechanical stresses involved in the grinding process. When gears are machined to precise tolerances, the grinding operation can introduce microfractures, especially in materials that have been case-hardened, since the hard outer layer can be more susceptible to such cracking.

In this scenario, the indications are observed on multiple teeth, which is characteristic of grinding cracks as they often appear in clusters on surfaces that have undergone extensive grinding. This further supports the identification of the cracks as they are frequently associated with the grinding of high-hardness materials, which can lead to stress concentrations and subsequent cracks.

Understanding the type and cause of these indications is essential for assessing the integrity of the gear. Addressing grinding cracks in manufacturing processes is crucial to ensure reliability and performance in mechanical systems, especially in gears that transmit power and motion.