With industrial drawings and blueprint reading, as with other types of graphical representation, it is always advisable to follow the best industry practices current at the time:
1. Draw one part to one sheet of paper. If this is not practical, apply enough spacing between parts and draw all parts using the same scale. Otherwise, the scale should be clearly noted under each part's drawing. Standard parts such as bolts, nuts, pins, and bearings do not require detail drawings.
2. Always use decimals.
3. Lettering should be all in capitals.
4. Select a front view that best describes the part.
5. Omit hidden lines unless absolutely necessary to describe the shape of the object.
6. Consider data and dimensioning schemes based on feature relationships.
7. Place dimensions between views where possible.
8. Where possible, minimize mathematical equations.
9. Do not dimension hidden lines.
10. Check that the product is designed for manufacturability and that an inspection process is in place to check dimension accuracy.
Figure 7.22B Typical helical spring nomenclature.
11. Avoid duplicating dimensions; use reference dimensions if necessary to duplicate.
12. Dimension lines should not cross other dimension lines.
13. Dimension lines should not cross extension lines.
14. No dimensions should appear on the body of a part. Offset 0.38 inch from the object outline.
15. Place all dimensions for the same feature in one view if possible.
16. Extension lines can cross extension lines.
17. Use center marks in view(s) only where a feature is dimensioned.
18. Use centerlines and center marks in views only if a feature is being dimensioned or referenced; otherwise omit.
19. When multiples of the same feature exist in a view, dimension only one of the features and label 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 dimensioned feature.
20. Minimize the use of centerlines between holes; they add little value and clutter the object being drawn.
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