2. To describe an object completely, a drafter needs to define both the shape and the size of the object.
3. After all, a machinist cannot build a part, a carpenter cannot build a house, unless all the sizes on the drawing are accurate and complete.
4. Another name for size description is Dimensioning.
5. There are two main types of dimensions: Size and Location
7. There are two main Methods of dimensioning Unidirectional and Aligned
8. Unidirectional (ANSI Preferred)
9. Standards for dimensioning technique, dimension placement, and general rules for dimensioning are published in Dimensioning and Tolerancing, ASME Y14.5M-1994.
10. Dimensioning Techniques
11. DIMENSIONING INCLUDES MEASUREMENTS, NOTES AND SYMBOLS
12. PLACEMENT OF DIMENSIONS
13. ARROWHEADS SIZE AND STYLES
14. DIMENSIONING DIAMETERS
15. DIMENSIONING RADII which do not need their centers located
16. DIMENSIONING RADII when locating the radius center.
17. Decimal Inch Decimals are the ANSI standard.
Decimals are easier to add, subtract, multiply and divide than fractions.
Preferably, decimals should be rounded to two decimal places (Unless more precision is required).
18. Metric Where linear measurement are less than 10,000 millimeters, the millimeter is the standard unit of measure.
The abbreviation for millimeters (mm) is usually omitted when all dimensions are in millimeters.
The period is used as a decimal point only in English speaking countries, others use a comma.
19. Leading and Trailing Zeros
20. The following are a few basic rules that summarize what might well be a list of hundreds of very specific rules that apply to dimensioning. Review the list carefully. Make each of these items a part of your dimensioning practices.
21. Each dimension should be clearly shown and stated so that it can be interpreted in only one way.
22. Dimensions should not be duplicated or given on a drawing in two different ways.
23. Avoid dimensioning to hidden lines when possible.
24. Dimensions should be placed in the view where the best shape and true form are shown.
25. Avoid long extension and leader lines.
26. Place a dimension between views, especially if it applies to both views and will improve clarity.
27. Do not assume that a part is symmetrical. Dimension both sides of a symmetrically shaped part or use the centerline symbol or note to avoid confusion.
28. Spacing between dimensions should be consistent within a drawing.
29. Line up dimensions horizontally and vertically where possible.
30. Avoid crossing dimension lines or leaders where possible.
31. Make full use of notes, abbreviations, and symbols to show how many times a dimension applies. For example, use 2X in a note to designate that a detail specified in the note exists in two places on the drawing. Dimension separately if the times (X) designation would be confusing.
32. Good Luck!
