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A chamfer with a "lark's tongue" finish

A chamfer /ˈtʃæm.fər/ is a transitional edge between two faces of an object. Sometimes defined as a form of bevel, it is often created at a 45° angle between two adjoining right-angled faces.

Chamfers are frequently used in the design of carpentry, furniture, concrete formwork, mirrors, printed circuit boards, and to facilitate assembly of many mechanical engineering designs.

Terminology

A "chamfer" may sometimes be regarded as a type of "bevel", but the terms are often used interchangeably.

In furniture-making, a lark's tongue is a chamfer which ends short of a piece in a gradual upward curve, leaving the remainder of the edge as a right angle. Chamfers may be formed in either inside or outside adjoining faces of an object or room. They are also used to "ease" otherwise sharp edges, both for safety and to prevent damage to them.

By comparison, a "fillet"^[a] is the rounding-off of an interior corner, and a "round" (or "radius") the rounding of an outside one.^[1]

Carpentry and furniture

Chamfers are used in furniture such as counters and table tops to ease their edges;^[why?] when the edges are rounded instead, they are called bullnosed. Special tools such as chamfer mills and chamfer planes are sometimes used.

Architecture

Chamfers are commonly used in architecture, both for functional and aesthetic reasons. For example, 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.^[2]

Urban planning

Many city blocks in Barcelona, Valencia 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,^{[citation needed]} 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.

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  A chamfered sidewalk street corner in historic Ponce, Puerto Rico
  

  
  

  
  


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  The Great gate (Darwaza-i rauza) gateway to the Taj Mahal, having chamfered tower corners
  

  
  

  
  


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  A chamfered building and street corner on Barcelona's Passeig de Gràcia. Here the building is chamfered but the sidewalk/street has taken on a conventional, 90-degree layout, eliminating the loading zone or parking spaces.
  

  
  

  
  


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  The original Barcelona Eixample city block design, showing the chamfered corners of buildings and streets, and including gardens that never materialized.
  

  
  

  
  

Mechanical engineering

Chamfers are frequently used to facilitate assembly of parts which are designed for interference fit.

Glass mirror design

Outside of aesthetics, chamfering is part of the process of hand-crafting a parabolic glass telescope mirror.^[3] Before the surface of the disc can be ground, the edges must first be chamfered to prevent edge 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.^{[citation needed]}

Printed circuit board (PCB) design

Right angled and chamfered intersections of a PCB track

In traditional printed circuit board (PCB) designing, a chamfer may be applied to a right-angled edge of a conductive junction in order to physically strengthen the conductive foil at that location. Chamfering of junctions may also be applied in high-frequency PCB design in order to reduce reflections.^[4] In high-voltage engineering, chamfers and rounded edges are used to reduce corona discharge and electrical breakdown.

With modern computer-aided design, rounded curve transitions are often used instead of chamfers, to further reduce stress and improve evenness of electroplating.

See also

• Bevel

References

External links

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  The dictionary definition of chamfer at Wiktionary


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   "Chamfer" . Encyclopædia Britannica. 5 (11th ed.). 1911.