Engineering dimension(part 1)

 DIMENSIONING

(Reference check for more details)

Engineering dimension

Dimension Line

• A line terminated by arrowheads, Which indicates the direction and extent of a dimension

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Extension Line

• An extension line is a thin solid line that extends from a point on the drawing to which the dimension refers.  

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Leader Line

• A straight inclined thin solid line that is usually terminated by an arrowhead.

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👉Leaders may be terminated

without an arrowhead or dot if it ends within the outline of an object. with a dot if it ends within the outline of an object

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Arrowheads

• Arrowheads are drawn between the extension lines if possible.  If space is limited, they may be drawn on the outside.  

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Types of Dimensions

👉Linear distances  

They are usually arranged horizontally or vertically, but may also be aligned with a particular feature of the part.

 

👉Angles

Used to give the angle between two surfaces or  features of  a  part

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Spacing and Readability

• The spacing between dimension lines should be uniform throughout the drawing. 
• Do not dimension inside an object or have the dimension line touch the object unless clearness is gained.
• Dimension text should be horizontal which means that it is read from the bottom of the drawing.
• Dimension text should not cross dimension, extension, or visible lines.

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Correctly dimensioned

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• Dimension lines should not cross extension lines or other dimension lines.
• Extension lines can cross other extension lines or visible lines.  
• Extension lines and center lines should not connect between views.
• Leader lines should be straight, not curved, and point to the center of the arc or circle at an angle between 30 – 60

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Correctly Dimensioned

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Spacing and Readability

Dimensions shouldn't be duplicated or equivalent information given in two alternative ways. 

• If a reference dimension is used, the size value is placed within parentheses.

Duplicate dimensions

Exercise 👉Find the duplicate dimensions and cross out the ones that you feel should be omitted.

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Dimension Placement

• Dimensions should be placed in such a way as to enhance the communication of your design.  

                 👉Dimensions should be grouped whenever possible.Dimensions should be placed between views, unless clearness is promoted by placing some outside.

                 👉Dimensions should be attached to the view where the shape is shown best. Do not dimension hidden lines

                  👉Dimensions should be attached to the view where the shape is shown best.

                  👉Do not dimension hidden lines.

Exercise: 👉List the dimensioning mistakes and then dimension the object correctly.

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Correctly Dimensioned

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