In gear design, how is the top and bottom of gears related to crest and what corresponding element in screw threads?

In gear design, the crest of the gear teeth is analogous to the topmost point of the tooth profile, while the root refers to the lowest point, which is the space between adjacent teeth. This relationship is similar to the terminology used for screw threads, where the root is the lowest point of the thread profile, while the crest (or top) is the highest point of the thread.

The essence of this comparison is that both gears and screws utilize a tooth-like feature, where the height and depth of these features play a crucial role in their functionality. In gears, the driving force is carried through the contact points on the teeth, with the root being the point where the teeth are spaced apart and the crest being the point at which they engage with other teeth.

The other terms, while related to the geometry of gears or screws, do not directly correspond in the same way as the crest and root do. The flank of the tooth refers to the sloped surface connecting the crest to the root, rather than a distinct point like the root. The top land is a flat surface on top of the gear tooth but does not represent the lowest point in the profile. These distinctions highlight why the root is the most appropriate term to correspond with the crest in