AutoCAD
AutoCAD
The Vernier Caliper below is used to help understand the insertion
factor of a item in relation to a drawing using Inches, feet, or metric
mm, cm as a drawing unit.
Understanding drawing unitsIn AutoCAD I draw in a 1 to 1 scale. That is to say a box that is 12" x 12" is drawn 12" x 12". Or simply that things are drawn to their real life size. A drawing unit in AutoCAD can be thought of as one mile, yard, foot, inch, kilometer, meter, centimeter, millimeter. I have used one second per unit with a drawing once. Using any of the metric units is easy within AutoCAD. This is because all you have to do is move the decimal point right or left to write in kilometers to meters or millimeters. Unlike the American system that has no consistent difference from mile to yard to feet to inch. When a surveyor draws his plan his standard is to draw one unit equals one foot, 12". When an architect draws a plan he will usually use one unit equals one inch. The use of fractions within the american inch system complicates this discussion. Fortunately I yet to find a need to draw in units of a mile or yard much less fathoms (6'-0"). If I want to draw something from a metric definition I would either create a new drawing using decimal system and then import using a scale factor as above. Furthermore I could use a calculator to convert each dimension from one system to another before drawing a particular segment.This unit concept needs to be understood in the mind of the draftsman who is doing the work. The draftsman must provide his audience with something so that they understand what each dimension means. When a dimension is applied in the drawing a suffix may be added (mile, yard, meter, decameter). The suffix tells the reader of the drawing what the AutoCAD unit means (7.62mm, 7.62yrd or 7.62yard2). It is when the drawing is committed to paper that scale comes into play. What scale used is determined by the size of paper and available rulers with different scales printed on its edges. |
drawing units page
