Understanding Industrial Blueprints 193
- Avoid duplicating dimensions; use reference dimensions if necessary to duplicate.
- Dimension lines should not cross other dimension lines.
- Dimension lines should not cross extension lines.
- No dimensions should appear on the body of a part. Offset 0.38 inch from the object outline.
- Place all dimensions for the same feature in one view if possible.
- Extension lines can cross extension lines.
- Use center marks in view(s) only where a feature is dimensioned.
- Use centerlines and center marks in views only if a feature is being dimensioned or referenced;
otherwise omit. - When multiples of the same feature exist in a view, dimension only one of the features and la-
bel as “NumberX DIM,” meaning that the feature exists in that view a certain number of times.
For example, “4X .250” implies that in the view, there are four like dimensions for the dimen-
sioned feature. - Minimize the use of centerlines between holes; they add little value and clutter the object being
drawn.
7.6 STANDARDS.
The main international standards organizations for geometrical dimensioning and tolerancing are:
- ASME
- ANSI
- ISO
For blueprint production, whether the print is drawn by a human hand or by computer-aided draw-
ing (CAD) equipment, the American industry has adopted a new standard, ANSI Y14.5M. It standard-
izes the production of prints from the simplest on-site handmade job to single or multiple-run items pro-
duced in a machine shop with computer-aided manufacturing (CAM) software.
There exist standards and practices for creating technical drawings of mechanical parts and assem-
blies. The governing agency mainly responsible for setting the standards in the United States is ASME.
There are a number of documents that cover various aspects of mechanical drawings,including:
- ASME Y14.100 -2004 Engineering Drawing Practices
- ASME Y14.4M -1989 Pictorial Drawing
- ASME Y14.3M -Multi- and Sectional View Drawings
- ASME Y14.1-1995 Decimal Inch Drawing Sheet Size and Format
- ASME Y14.5M-1994 Geometric Dimensioning and Tolerancing
- ASME Y14.13M-1981 Mechanical Spring Representation
It is important that these standards are implemented and followed by the drafter to ensure that the
drawings are correctly interpreted by others.