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   Dimension to Centerlines When it Makes Sense

Many past Tips have illustrated dimensioning from and to center lines. There continues to be questions about when it is okay to dimension with center lines and when it is not appropriate. Dimensions may be to and from center lines on a drawing if the dimensions are basic and the center line is representing the:

  • axis, center point or centerplane of a feature of size
  • center of a pattern such as a bolt pattern
  • center of a radius
  • center of a slot length or width 

In all of these cases if direct tolerancing is used, confusion may result. There is no reason to have this confusion except to fall back on "that's the way we've always done it". If you always do what you've always done, you'll always get what you've always got. In other words, you will never improve. The drawing below shows the common correct application of dimensions to center lines. In every case the dimensions to and from the center lines are basic.

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