Appendix 3: Color, Linetype and Line Weights – Machine Drawing with AutoCAD

Appendix 3

Color, Linetype and Line Weights


AutoCAD provides the facility to control the properties of an object such as color, linetype, line thickness, and so on, as per the requirement of the user. At times it may be essential to assign different colors to different objects in the same layer so that the understanding of the drawing is improved. There are instances when it is necessary to specify a fixed color for a layer to have all the objects drawn on that layer look alike.

You may also use different line types in your drawing to represent object outlines, hidden lines, center lines, and so on. The linetypes are controlled by setting the same in AutoCAD. Similarly, you can adjust the line thickness by controlling the line weights as referred to in AutoCAD environment. You can find all these control tools on the Object Properties toolbar, as shown in Fig. A3.1.


FIG. A3.1


When you start a new drawing, all the objects are drawn in a color set through ByLayer as displayed in the color control box. It means that all the objects you draw in a layer will be drawn with the color assigned to that layer (Refer discussion on layer). You know already that initially layer 0 is set as the only default current layer. Generally its default color is white (if your screen color is white, then it will be black).

AutoCAD has 255 regular colors and 2 additional color properties. You can use the first seven colors by name. They are red, yellow, green, cyan, blue, magenta, and white (black). To set the current color, choose a color from the Color Control drop down list on the color control box. It shows seven colors and two special colors ByLayer and ByBlock. If you want to change the color of an object, select any color from among these seven colors or click the Other button at the bottom of the list to open the Select Color dialog box to choose from several other color options. Each color in this dialog box has a preset numerical value and when you select any of these colors, that number will be displayed in the color control box.

You may also select ByLayer or ByBlock. These will force all the objects to adopt the color assigned to the layers to which they individually belong or of the block into which they are grouped.



You can display the Select Color dialog box by any one of the following methods.


If you want to change the color of any object in your drawing, the easiest way is to grip select that object by clicking it and then selecting the color you want to assign from the drop down menu (including the other colors). The dotted outline of the object in the grip selected stage changes color to the selected color. Press the Esc button twice to get rid of the grips. The color of the object will change.

You can also change the color of an object by changing the color of the layer to which it belongs; all objects of that layer will also change color. Or, open the Properties window after grip selecting the object and change the color from the Characteristics list.


According to engineering drawing convention, it is essential to use different linetypes, for example, dashed line, center line, continuous line and so on to represent various characteristics of a drawing.



You create an object in AutoCAD by using the current linetype. This current linetype, by default, is fixed by the linetype assigned to the current layer. So, with the ByLayer setting on, you can change the linetype of a particular layer by changing the linetype assigned to it. All the objects drawn on that layer will change to the new linetype.

A very important setting option for the linetype is the ByBlock. When this setting is on, you can draw only with the continuous linetype. However, when you group these objects to form a block they will inherit the linetype character of the layer where the group is inserted.

However, you can always override the layer setting for the linetype of a particular object by selecting a different linetype from the drop down linetype box of the object properties toolbar as shown in Fig. A3.2. The object will be now drawn with the new linetype instead of the linetype assigned to the current layer. Changing the linetype of the layer now, therefore, will have no effect on these new lines.

To set the linetype as current, select it from the dropdown Linetype Control box on the drawing properties toolbar. Click the box and it becomes the current linetype.

AutoCAD has 45 predefined linetypes. You can also create your own linetypes. However, all these linetypes (including user-defined linetypes) are not usually available in the list. In order to use them, you have to load them from a library file through the Linetype Manager dialog box. For displaying this dialog box, you may do one of the following.


FIG. A3.2   The Linetype Control dropdown list


When the command is initiated, AutoCAD displays the Linetype Manager dialog box (Fig. A3.3) which lists all the available linetypes.

  1. In the Linetype Manager dialog box click Load. AutoCAD will display the Load or Reload Linetypes dialog box as shown in Fig. A3.4.


    FIG. A3.3   The Linetype Manager dialog box


    FIG. A3.4   The Load or Reload Linetypes dialog box


  2. Select one or more linetypes to load from the available list and click OK. AutoCAD will display these selected linetypes in the drop down list of the Linetype Control drop down list on the Object Properties toolbar.
  3. Now you can select any one of these lines from the current list of linetypes available from the dropdown list of the Object Properties box and make it current (as described before) for your use.

Sometimes the dashed line in a drawing appears to be continuous on the screen. This happens because of the Linetype Scale Factors or the Ltscale factor. You have to manipulate this scale factor to get a proper display of dashed lines. Suppose a linetype is originally defined with a sequence of dashed lines and blank spaces, each 0.25 units long. Then this designed spacing and dashes will actually measure 0.25 when you use a Ltscale factor of 1. Now if you change the Ltscale factor to 0.5, the length of each line and space will become 0.125; if you change them to 2, they will become 0.50 units long (Fig. A3.5).

Now, if a line segment is too short to hold even one dash sequence, AutoCAD will draw a continuous line, if you set a very large value for the Ltscale factor then too AutoCAD will draw a continuous line. That is why when the drawing scale is too large or too small, the Ltscale factor has to be adjusted to control the appearance of the dashed lines.


FIG. A3.5   Different Ltscale factors


FIG. A3.6   Different Ltscale with different Global scale factors


AutoCAD initially draws all non-continuous linetypes with a Global Ltscale factor of 1. Now when you control the Ltscale factor on object basis, the current Linetype Scale factor is multiplied by the Global Linetype Scale factor. Therefore, if you draw a line with object Ltscale factor set to 0.5 in a drawing in which the Global Scale factor has been set to 2, the equivalent scale factor will be equal to 2 and the lines will appear on the screen accordingly (Fig. A3.6). You can change the Ltscale factor applicable to the whole drawing (Global Ltscale factor) by the Ltscale command when AutoCAD will ask you to enter the new Ltscale factor while showing the current value. You can control both the Global and the Object Ltscale factors from the Linetype Manager dialog box (Fig. A3.7) using the following steps.


FIG. A3.7   Expanded area of the Linetype Manager dialog box


  1. Choose Linetype from the Format menu.
  2. Enter the Global and the current Object Scale factors. Remember that the Global Scale factor will change the scale factors of all the existing and new objects while the current Object Scale factor will change the scale factors of the subsequently drawn objects.

In AutoCAD, you can draw lines with different line weights. This facility is useful in engineering drawing where different line thicknesses are used for different purposes. AutoCAD has 23 valid lineweights to choose from—a range of 0.05 mm to 2.11 mm (0.002 inches to 0.083 inches). It also has options for choosing lineweights as ByLayer, ByBlock as before, along with two new options – 0 and Default. If you select the 0 option, lines will be displayed using one pixel and the finest line possible will be plotted in the printer/plotter. The default value is usually set at 0.25 mm (0.01 inch) which can be changed to another valid line weight. Any value equal to or less than the default value will be displayed with one pixel but will be plotted as per the assigned lineweights.



To set the current lineweight, select the lineweight from the dropdown menu of the Drawing Properties toolbar. The use of ByLayer and ByBlock are the same. You may not see the effect of the changed lineweights when you opt for a new lineweight because, by default, AutoCAD does not show the lineweights. To see the effect, you have to press the LWT button on the status bar or to give the LwDisplay command and press Enter and then change the system variable value from 0 (off) to 1 (on).

The display and other controls of lineweight are actually controlled by the lineweight settings dialog box which can be revoked by any one of the following actions.

Fig. A3.8 indicates the various operations that can be performed the Lineweights Settings dialog box. The guide arrows clearly explain the various operations that could be performed in the dialog box. A lineweight list shows how the various standard lineweights will be displayed in the Model space at the current scale. Controlling the lineweights plays a major role during the plotting of a drawing.


FIG. A3.8   The Lineweight Settings dialog box


A very popular and useful way of changing the common properties of an object quickly is to use the Properties window. The eight common properties that can be edited through this window are Color, Layer, Linetype, Linetype Scale, Plot Style, Lineweight, Hyperlink, and Thickness.

The Properties dialog window can also be opened by holding down Ctrl + 1 (number 1 key) or Grip select an object.



FIG. A3.9   The Properties Window


The window contains a dropdown box that lists all selected objects. All the information specific to the type of object selected are classified under two tabs, namely, Alphabetic and Categorized. They contain properties which can be viewed or edited.

Fig. A3.9 shows the Properties window of a circle. If you want to change the color of the circle, pick the color cell and an arrow will appear for picking a color from the drop-down list. If you click select one of the colors, the color of the object in the drawing selected changes to that color. Close the box to return to your drawing and press Esc twice to get rid of the grips.

In the same way, arrows will appear in the layer, linetype, lineweight, and plotstyle cells. In the cells for Ltscale and thickness enter the value you want to opt for. You are advised to practice changing some of the most visible properties of any drawn object of your drawing by using this window for gaining control over its uses. Remember that when you select more than one type of object, the window will show the numbers of each type in a bracket, such as Circle (2). You can use the dropdown list at the top to edit just one type of object by selecting the type, for example Arc (3), whereby all the properties of the arc will change.

However, if you choose more than one object of the same type, say circles, and then edit any of their properties, all the circles selected will be affected.

You can also change the position of an object by changing its coordinate from the list. You can pick the cell and use the pick point button to show the new position on your drawing also.

Similarly you can use the older variety of the Properties window–the Object Properties window which is found under the modify menu. By Object Properties you can edit the common properties of a group of objects as well as a single object. Since the operation is the same, it is not being discussed separately.