AutoCAD® 2009 & AutoCAD LT® 2009 All-in-One Desk Reference for Dummies®

Chapter 7. Precision Tools

The purpose of creating technical drawings, or drafting, is to convey enough information to a builder or fabricator so that he or she can construct or manufacture whatever it is that you've just technically drawn . . . er, drafted.

Manual drawings are as precise as the drafter can make them, which means as precise as a mechanical pencil dragged against a parallel rule or drafting machine. They're good enough to get the job done because the dimensions are going to confirm sizes and notes.

Dimensioning can be a major job in manual drafting, and luckily, you have an extra tool at your disposal with AutoCAD: You can add dimensions by clicking objects or selecting points. AutoCAD extracts the dimension value and adds the correct text to the dimension. Now, if you are precise in your drafting, the dimension values will be perfect, but if you are sloppy . . . you may be hearing from the builder that you've asked to locate a wall 12′–6 29/256″ from the corner!

This chapter tells you how to make use of AutoCAD's built-in drafting aids to create accurate and precise drawings.

Understanding Accuracy and Precision

You probably hear a lot of sloppy word usage in the technical-drawing field. One of the most common offenses is the idea that accuracy and precision mean the same thing. They're different, and here's how:

• Precision means the degree of fineness of measurement. AutoCAD is capable of extremely high levels of precision — and can create drawings much more precisely ...