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A chamfer /ˈʃæm.fər/ is a transitional edge between two faces of an object. It can also be known as a bevel but connotes more often cutting and is more often 45° with respect to the two adjoining faces. If the un-chamfered intersection of the adjoining faces would otherwise form a right angle, 90° as is most common, the chamfer will typically be uniform and pitched at 45° . A fully chamfered square interior would thus be octagonal. (By contrast, a fillet is the rounding-off of an interior corner, and a rounding of an exterior corner is called a "round" or a "radius")
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"Chamfer" is a term commonly used in mechanical and manufacturing engineering. Special tools such as chamfer mills and chamfer planes are available. In tile work, or furniture such as counters or table tops, an edge or arris that has been eased by rounding instead of chamfering is called a bullnose. Where a chamfer does not go to the end of the piece, but "lifts out" in a smooth curve, the end is called a lark's tongue.
In non-aesthetic uses, chamfers are necessary in parabolic glass mirror manufacture and desirable in certain printed circuit boards. A chamfer is also often used to make an otherwise sharp edge safer when a machined metal part is intended to be handled by a person.
Architecture
In architecture, the base of the Taj Mahal is a cube with chamfered corners, thereby creating an octagonal architectural footprint. Its great gate is formed of chamfered base stones and chamfered corbels for a balcony or equivalent cornice towards the roof.
Many city blocks in Barcelona, València and various other cities in Spain, and street corners (curbs) in Ponce, Puerto Rico, are chamfered. The chamfering was designed as an embellishment and a modernization of urban space in Barcelona's mid-19th century Eixample or Expansion District, where the buildings follow the chamfering of the sidewalks and streets. This pioneering design opens up broader perspectives, provides pleasant pedestrian areas and allows for greater visibility while turning. It might also be considered to allow for turning to be somewhat more comfortable as, supposedly, drivers would not need to slow down as much when making a turn as they would have to if the corner were a square 90 degrees, though in Barcelona, most chamfered corners are used as parking spaces or loading-unloading zones, leaving the traffic to run as in normal 90-degree street corners.
In parabolic glass mirror design
Outside of aesthetics, chamfering is part of the process of hand-crafting a parabolic glass telescope mirror. Before the surface of the disc can be ground, the edges must first be chamfered to prevent chipping. This can be accomplished by placing the disc in a metal bowl containing silicon carbide and rotating the disc with a rocking motion. The grit will thus wear off the sharp edge of the glass.
In printed circuit board (PCB) design
In printed circuit board (PCB) designing, a chamfer occurs when a right-angled edge is eliminated from the tracks, to strengthen the places where a track meets another at a right angle. It also reduces reflections, which is important for high-frequency design.