Engineering Drawing - Dimensioning and Sectioning

Topics: Dimension, Technical drawing, Engineering drawing Pages: 4 (1118 words) Published: February 27, 2013
Dimensioning Fundamentals
By William Bussard, March 2004
* Dimension lines: Lines located between extension lines ending with an arrow and to include a numerical value. They should be spaced uniformly approximately .375 to .500 inches apart. * Extension lines: Extend away from a view to indicate a size or location constraint origin. When extension lines cross object or extension lines, no gap in either line should be made. * Leader Lines: Lines drawn at an angle (never horizontal or vertical) extending from a note to a feature to which the note applies.  

Dimension and Extension line placement
1. Always place shorter dimensions nearest to the object lines. Dimension lines should never cross. However, extension lines may cross each other. 2. Extension lines should never be shortened.

3. Dimension lines should never coincide with any object line or center line of the drawing. Therefore no line should be used as dimension line nor coincide with a dimension line. 4. Dimensions should line up in chain fashion or be grouped together as much as possible. 5. Do not repeat a dimension.  Repeating a dimension will only confuse the reader and could cause errors in the manufacturing process. 6. Dimensions should be given in views where the shapes are presented in profile and/or contour. 7. Dimensions should always be placed off or outside of a view where possible. 8. Hole features must be located and given size in the view where they appear as a circle not as a rectangle or hidden lines. Never dimension to hidden lines. 9. Avoid a complete chain of dimensions. Either omit one or use reference notation. Reference notation indicates that a dimension is used for information purposes only. Indicate a reference dimension by placing a parenthesis around the dimension 10. Cylinder location and size constraint. Locate cylinders in the circular view but give its diameter and length in the rectangular view....
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