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- | Written by Allan Wise | + | Written by Allan |

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| Created 2-July-2004 | | Created 2-July-2004 |

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- | Lines | + | ==Lines== |

- | Projection lines indicate extremities of a dimension. A gap of 1mm is generally drawn from the object to the start of the projection line. An extension of 2mm is generally drawn past the dimension line. | + | *Projection lines indicate extremities of a dimension. A gap of 1mm is generally drawn from the object to the start of the projection line. An extension of 2mm is generally drawn past the dimension line. |

- | Dimension lines run between the projection lines. They generally terminate with and arrowhead or tick. Arrowheads are usually 3x1mm and ticks, 2mm long. | + | *Dimension lines run between the projection lines. They generally terminate with and arrowhead or tick. Arrowheads are usually 3x1mm and ticks, 2mm long. |

- | Thin linework should be used of dimension and projection lines. | + | *Thin linework should be used of dimension and projection lines. |

- | For dimensions that cannot be drawn to there true termination point, the free end is terminated in a double arrowhead. | + | *For dimensions that cannot be drawn to there true termination point, the free end is terminated in a double arrowhead. |

- | 15 x scale is the formula for working out the gap between dimension lines and the object. | + | *15 x scale is the formula for working out the gap between dimension lines and the object. |

- | Notation | + | |

- | Dimensions are usually in millimetres (millimeters). Place a note in the title block stating "ALL DIMENSIONS IN mm" to avoid the need to specify "mm" after every number. | + | |

- | Dimensions lest than 1 should lead with a "0" before the decimal point. Example: 0.5 | + | |

- | Angular dimesions are specified in decimal degrees, degrees and minutes or degrees minutes and seconds. Example: 10.5° - 10°30' - 10°30'30" | + | |

- | When specifying an overall dimension, one non-critical component dimension should be omitted. Where all component dimesions must be specified, and overall lenght should be specified as an auxiliary dimension. | + | |

- | Auxiliary dimensions should be shown in brackets or noted "REFERENCE". | + | |

- | Dimensions that are not to scale are underlined or noted "NTS". | + | |

- | Where the "plus minus" symbol appears after a number, the number has been rounded of to the nearest whole number. Generally this is not required, unless in clears up why a dimension string does not close off. | + | |

- | Alignment | + | |

- | There are two common methods of aligning notations, "Aligned" is the most common. | + | |

- | Aligned: The dimensions are parallel to the dimension line. Dimensions can always be readable either from the bottom or the right of the drawing. | + | |

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- | Unidirectional: All dimensions are written horizontally. | + | ==Notation== |

| + | *Dimensions are usually in millimetres (millimeters). Place a note in the title block stating "ALL DIMENSIONS IN mm" to avoid the need to specify "mm" after every number. |

| + | *Dimensions lest than 1 should lead with a "0" before the decimal point. Example: 0.5 |

| + | *Angular dimesions are specified in decimal degrees, degrees and minutes or degrees minutes and seconds. Example: 10.5° - 10°30' - 10°30'30" |

| + | *When specifying an overall dimension, one non-critical component dimension should be omitted. Where all component dimesions must be specified, and overall lenght should be specified as an auxiliary dimension. |

| + | *Auxiliary dimensions should be shown in brackets or noted "REFERENCE". |

| + | *Dimensions that are not to scale are underlined or noted "NTS". |

| + | *Where the "plus minus" symbol appears after a number, the number has been rounded of to the nearest whole number. Generally this is not required, unless in clears up why a dimension string does not close off. |

| + | |

| + | ==Alignment== |

| + | *There are two common methods of aligning notations, "Aligned" is the most common. |

| + | # Aligned: The dimensions are parallel to the dimension line. Dimensions can always be readable either from the bottom or the right of the drawing. |

| + | # Unidirectional: All dimensions are written horizontally. |