FLANK

The flank is the lateral wall of a part, the surface that forms its perimeter or thickness. In watchmaking, the term is commonly used for components andExternal parts (case, dial, hands): the flank of aBridgeor aMain plate, the flank of a wheel (the thickness of itsRim), the flanks of aCase middleor aHorn (lug)ofCase. Flanks are highly visible surfaces and, as such, are often finely worked: polished, satin-finished, beveled (chamfered and polished on the edges), even diamond-cut, they fully contribute to the perceived quality of amovement or a case. On movement components, the treatment of flanks — notably the Beveling / Angling of the edges — is a major criterion of fine watchmaking. On the external parts (case, dial, hands), the Vibration of polished and brushed flanks structures the set of Light of the case. Technically, the flank of a tooth refers to the lateral face of a tooth, whose profile (involute, epicycloid) determines the quality of meshing. The context clarifies the meaning: the lateral surface of a part, or the face of a tooth of a Gear.