Anglage
This is one of the most exacting and demanding finishes to apply. The description sounds simple: anglage consists of a rounding and polishing of the edge of a movement bridge or other component. There are multiple purposes that underlie application of anglage. First and foremost is the elimination of smudges and burs remaining after a part has been machined. Not only are these “left overs” from the cutting of the component unappealing in appearance, they are prime sites for corrosion to begin.
The challenges in creating a perfect anglage finish are many, even with the simplest of forms, but increase geometrically as the shape of the component becomes more complex. Consider for a moment the panoply of shapes at the disposal of watchmakers as they craft the bridges, plates, cams and levers of different movements: straight edges, sharp exterior corners, rounded bombée edges. The palate is essentially endless, limited only by the imaginations of the movement designers. And it is this boundless variety that calls up a broad repertoire of skills and talents for the watchmakers who practice the craft of anglage. Take, for example, an interior angle (“angle rentrant”). This is an interior corner or intersection, a shape found on many bridges. It is essentially impossible to form an interior corner perfectly when a part is machined.
Careful hand filing with a parade of different metallic files (some coarse, some fine, different widths, etc.), followed by even finer polishing with diamond paste impregnated peg wood, are required to achieve a perfect form with gleaming rounded angles coming together cleanly at the interior intersection.
The requirements for finely done anglage are strict. Notwithstanding the variance in possible outside edge shapes of the component, the rounding should be even throughout. Irregularities, flat spots, distortion of curves are all unacceptable. Most of all the edges should display a clean bright polish, done in a way to maximize brilliance.
