Set up dimension in CAD
To set up dimension in CAD, firstly you must know dimension elements of CAD. A specified dimension includes the following major elements:
- Dimension line: Dimension line is limited by 2 arrows (slash or any symbol). If it is linear dimension, it is perpendicular with extension lines. If it is angular dimension, it is an arc with the center at vertex. In the case, you specify dimension of symmetric element, dimension line is drawn over symmetric axis without drawing the second arrow. When the center of arc is outside of limit to draw, dimension line of radius is broken or dashed without defining the center.
- Extension line: In general, extension line is the straight line which is perpendicular with dimension line. However, you can edit it to be oblique with dimension line. Extension line is extended over dimension line with a segment which equals 2 to 3 times the width of basic line. Two extension lines of a same dimension must be parallel with each oher.
- Dimension text: Dimension text is the size of the object specified dimension. In dimension text, you can specify tolerance, enter prefix, suffix of dimension. The height of dimension text in technical drawings is the standard value. In general, dimension text lies inside; if there is not enough space, it will lie outside. Unit of length following to Meter system is mm, on drawing you do not need to specify measurement unit. If using other units of length such as centimeter or meter, measurement unit is specified after dimension text or in the annotation of drawing. Arrowheads (Arrow, slash):
° Symbol at two heads of dimension line is commonly arrow, slash, dot or any block you create. In AutoCAD, there are 20 types of arrow available. Two arrows which are drawn inside limit dimension line. If there is not enough space, they will be drawn outside. It is allowed to replace two opposite arrows by a bold dot.
° For radius and diameter dimension, there are 4 dimension elements: dimension line, arrow (slash), dimension text and center mark or center line. At that time, we consider circler or arc to be extension lines.
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