(3) GD&T Symbols - Diameter, Radius, Controlled Radius and Spherical Radius/Dia

• Diameter (ø) -
  Indicates a circular feature when used on the field of a drawing or indicates that tolerance is  diametrial when used in a feature control frame.
                 OR
   Diameter symbol replaces the word "Diameter". It should be used anywhere there is a diameter on the drawing,abd when a tolerence zone is cylindrical.
  
  Ex-
  
  
  
• Radius (R)-   A straight line extending from the center of an arc or circle to its surface.
  
  
  EX-
  
  
  
  
  

Controlled Radius (CR)-  Creates a tolerance zone defined by two arcs (the minimum and maximum radii) that are tangent to the adjacent surfaces. Where a controlled radius is specified, the part contour within the crescent-shaped tolerance zone must be a fair curve without flats or reversals. Additionally, radii taken at all points on the part contour shall neither be smaller than the specified minimum limit nor larger than the maximum limit.
The Abbreviation CR is defined by 1994 standard to indicate a controlled radius dimension.

• Spherical Radius (SR) Or Spherical Diameter (Sø)- 
  
  Spherical Diameter - shall precede the tolerance value where the specified tolerance value represents spherical zone. Also, a positional tolerance may be used to control the location of a spherical feature relative to other features of a part. The symbol for spherical diameter precedes the size dimension of the feature and the positional tolerance value, to indicate a spherical tolerance zone.
  
  SR
  Spherical Radius - precedes the value of a dimension or tolerance.
  
                               OR
  Spherical Features may be dimensioned by giving either the radius of diameter of a sphere.
  
  Ex-
  

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