All dimension and note text must be oriented to be read from the bottom of the drawing (relative to the drawing format). Placement of all text to be read from the bottom of the drawing is called unidirectional dimensioning . Aligned dimensions have text placed parallel to the dimension line with vertical dimensions read from the right of the drawing sheet. Dimensions are to be kept outside of the boundaries of views of objects wherever practical. Dimensions may be placed within the boundaries of objects in cases where extension or leader lines would be too long, or where clarity would be improved. If it is necessary to include a dimension that is out of scale, the out of scale dimension text must be underlined. The symbol X is used to indicate the number of times a feature is to be repeated. The number of repetitions, followed by the symbol X and a space precedes the dimension text. 9.3 DETAIL DIMENSIONING Holes are typically dimensioned in a view which best describes the shape of the hole. Diameters must be dimensioned with the diameter symbol preceding the numerical value. When holes are dimensioned with a leader line, the line must be radial. A radial lin e is one that passes through the center of a circle or arc if extended. When it is not otherwise clear that a hole extends completely through a part, the word THRU shall follow the numerical value. Symbols may be used for spotface, counterbore, and countersunk holes. These symbols always precede the diameter symbol. The depth symbol may be used to indicate the depth of a hole. The depth symbol is placed preceding the numerical value. When the depth of a blind hole is specified, it refers to the depth of the full diameter of the hole. When a chamfer or countersink is placed in a curved surface, the diameter given refers to the minimum diameter of the chamfer or countersink. If the depth or remaining thickness of material for a spotface is not given, the spotface depth is the smallest amount required to clean up the material surface to the specified diameter. Chamfers are dimensioned by providing either an angle and a linear dimension or by providing two linear dimensions. Chamfers of 45 degrees may be specified in a note. Slotted holes may be dimensioned any of several ways depending on which is most appropriate for the application.
Keyseats are dimensioned in a particular way, because they present some unusual problems. Summary of current (Y14.5-1994) and previous dimensioning standards used for various features. The diameter is specified for holes and blind holes. Blind holes are ones that do not go through the part. If the hole does not go through, the depth is specified, preceded by the depth symbol. Holes with no depth callout are assumed to go through.
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- Fall '09
- numerical value, LMC