Location of Features

Rectangular coordinate or polar coordinate dimensions locate features with respect to one another, and as a group or individually, from a datum or an origin. The features that establish this datum or origin must be identified. See para. 7.2.1.3. Round holes or other features of symmetrical contour are located by giving distances, or distances and directions, to the feature centers.

  1. Rectangular Coordinate Dimensioning
  2. Rectangular Coordinate Dimensioning Without Dimension Lines
  3. Tabular Dimensioning
  4. Polar Coordinate Dimensioning
  5. Repetitive Features or Dimensions
  6. Use of X to Indicate “By”

Rectangular Coordinate Dimensioning

Where rectangular coordinate dimensioning is used to locate features, linear dimensions specify distances in coordinate directions from two or three mutually perpendicular planes. See Fig. 1-49. Coordinate dimensioning must clearly indicate which features of the part establish these planes. For methods to accomplish this, see Figs. 4-2 and 4-8.


Rectangular Coordinate Dimensioning Without Dimension Lines

Dimensions may be shown on extension lines without the use of dimension lines or arrowheads. The base lines are indicated as zero coordinates. See Fig. 1-50.


Tabular Dimensioning

Tabular dimensioning is a type of rectangular coordinate dimensioning in which dimensions from mutually perpendicular planes are listed in a table on the drawing, rather than on the pictorial delineation. See Fig. 1-51. Tables are prepared in any suitable manner that adequately locates the features.


Polar Coordinate Dimensioning

Where polar coordinate dimensioning is used to locate features, a linear and an angular dimension specifies a distance from a fixed point at an angular direction from two or three mutually perpendicular planes. The fixed point is the intersection of these planes. See Fig. 1-52.


Repetitive Features or Dimensions

Repetitive features or dimensions may be specified by the use of an X in conjunction with a numeral to indicate the “number of places” required. See Figs. 1-53 through 1-57. Where used with a basic dimension, the X may be placed either inside or outside the basic dimension frame. A space is used between the X and the dimension. See Figs. 4-39 and 7-16.

Series and Patterns.

Features, such as holes and slots, which are repeated in a series or pattern, may be specified by giving the required number of features and an X followed by the size dimension of the feature. A space is used between the X and the dimension. See Figs. 1-53 through 1-57.

Spacing.

Equal spacing of features in a series or pattern may be specified by giving the required number of spaces and an X, followed by the applicable dimension. A space is used between the X and the dimension. See Figs. 1-55 through 1-57. Where it is difficult to distinguish between the dimension and the number of spaces, as in Fig. 1-55, one space may be dimensioned and identified as reference.


Use of X to Indicate “By”

An X may be used to indicate “by” between coordinate dimensions as shown in Fig. 1-43. In such cases, the X shall be preceded and followed by one character space.

NOTE: Where the practices described in paras. 1.9.5 and 1.9.6 are used on the same drawing; care must be taken to be sure each usage is clear.


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