Dimensioning with AutoCAD - Section 6

CHAPTER 27: DECREASE

As we wanted to reflect in the title of this guide, drawing in Autocad usually aims to bring the drawing of the screen to reality. For this to be possible, the theory of technical drawing establishes two indispensable requirements that must be fulfilled if, for example, something has been drawn that has to be manufactured in a workshop: that the views of the drawing do not give rise to doubts about its form and that the description of its size is accurate. That is, that the drawing is correctly bounded.
We therefore understand by dimensioning the process of adding measurements and notes to drawn objects so that they can be created. As we have insisted throughout this work, the possibility that Autocad gives to draw the objects at their "real size" (in drawing units), also allows the dimensioning process to be automated, since it is not necessary to capture measurement values.
In fact, as we will see in this chapter, the tools that Autocad offers to limit are so simple to use, that it is enough with a brief review of its characteristics so that the reader can handle them quickly. However, this simplicity in use can lead to error in users who do not master the criteria established in the technical drawing. The fact that Autocad allows to point two points so that a dimension is automatically generated from there, does not mean that this dimension is correct.
So, although it seems unnecessary, let's see the anatomy of a typical dimension, the elements that compose it, other aspects that we must take into account and briefly review the basic criteria for its use; then we will study the tools to limit that Autocad offers, the definitions that correspond to it according to its type and some application examples for each one of them.

 

Agree? Okay. Agree.

27.1 Criteria for limiting

To add dimensions to a drawing we have these basic criteria:

 

1.- When we create a drawing with several views of the same object, we must place the dimensions between the views, whenever this is possible (In the 29 chapter we will see how to automate the creation of views with graphical windows).

2.- When the shape of an object forces us to create two parallel dimensions, the smaller dimension must be closer to the object. The program's “Baseline Dimension” tool does this for you, but if you don't use it and then need to add a minor dimension parallel to another already created, don't forget its correct location.

3.- The dimensions should preferably be in the view that best shows the characteristic shape of the object. In the following example, 15 measurements might be in the other view, but would poorly reflect their shape.

4.- If the drawing is large enough, the dimensions can be in it if the detailed measurements require it.

5.- A quota must not be repeated in two different views. On the contrary, different details must be considered, even when they measure the same.

6.- In small details, we can change the criteria of signaling limits of the dimensions, to improve its presentation. As we will see later, it is possible to modify the parameters of the dimensions to fit these needs.