AutoCAD linetype customizing facilities

Once upon a time, a long time ago, in an AutoCAD release very far away, someone decided that AutoCAD should draw using a variety of noncontinuous linetype styles. Someone further decided that the people at Autodesk, as smart as they were, could not forsee every possible type of noncontinuous linetype that users might desire or require, so in their great wisdom they allowed users to create their own custom line definitions.

AutoCAD has 46 standard linetypes defined. For the most part, the 46 cover every conceivable situation. We will begin by looking at the current ones and then investigate the need for and method of defining other styles.

What’s available
As usual these days, AutoCAD has umpteen different ways start a specific command. Whenever I mention a specific way in a column, I get inundated with e-mail telling me about the other umpteen minus one ways. I know, but I don’t have space to list them all here.

Anyway, issue either the Layer or Linetype command from the Command prompt, or go to Format|Layer, or Format|Linetype, or use the Object properties toolbar and pick Layer or Linetype, or whatever.

Pick the Linetype tab of the Layer and linetype dialog box to see the 46 linetypes.

What 46? I see only three.

You’re right. Initially, new drawings show only three types. First, the explanation of continuous is pretty obvious. In fact, its definition is built in by default.

Two other names also turn up, but they are not really linetypes. Bylayer simply means that the object takes on the linetype properties of the layer on which it resides. Byblock means that if you use an object in a block definition, the object within the block takes on the linetype properties of the layer in which you insert the block.

To see the other 45 linetypes, load the definitions from an external file. From the Linetype tab of the Layer and Linetype dialog box, pick Load. This defaults to the linetype definitions stored in the external file called ACAD.LIN, as shown in figure 1 below.

Figure 1. Each linetype definition has a name and a description in ACAD.LIN.

Each linetype definition has a name and a description. The description includes a series of dashes and dots that show approximately what the linetype looks like. As you can see, linetypes cover ISO (metric) styles and Imperial styles for things such as hidden, section, center, and phantom lines. Most are also available in regular, half, and double scales.

You usually use the Ltscale and Celtscale commands to set a specific linetype scale for all objects globally or for specific objects within the drawing, but you can also select fine and coarse variants of linetypes.

Select one or more linetypes, click OK, and the selected linetypes become available in your drawing.

Cool, but for drawing schematic drawings I need linetypes to indicate different line contents such as pneumatic, hydraulic, hot water, cold water, and so on.

Season of our dis-contents
Note that you had to load the desired linetypes from an external file. That file is a simple text file. To add or create custom linetype definitions, you can either edit the external file with Notepad or create your own separate file. If you edit the standard ACAD.LIN file, save an original copy somewhere so you can go back. If you don’t, the file is always available from the install CD-ROM.

The standard ACAD.LIN file resides in the AutoCAD Program files\……\Support directory. In Notepad you;ll see that the first portion looks almost exactly like this:

;;
;; AutoCAD Linetype Definition file
;; Version 2.0
;; Copyright 1991, 1992, 1993, 1994, 1996 by Autodesk
;;
*BORDER,Border __ __ . __ __ . __ __ . __ __ . __ __ .
A,.5,-.25,.5,-.25,0,-.25
*BORDER2,Border (.5x) __.__.__.__.__.__.__.__.__.__.__.
A,.25,-.125,.25,-.125,0,-.125
*BORDERX2,Border (2x) ____ ____ . ____ ____ . ___
A,1.0,-.5,1.0,-.5,0,-.5
*CENTER,Center ____ _ ____ _ ____ _ ____ _ ____ _ ____
A,1.25,-.25,.25,-.25
*CENTER2,Center (.5x) ___ _ ___ _ ___ _ ___ _ ___ _ ___
A,.75,-.125,.125,-.125
*CENTERX2,Center (2x) ________ __ ________ __ _____
A,2.5,-.5,.5,-.5

The rest of this line includes the actual definition of the linetype segments. The definition of each segment is a simple numeric value, separated by a comma (no spaces) from its neighbors, that indicates its nominal length. Positive values indicate pen down, or draw a line. Negative values indicate pen up, or leave a blank segment. A length of zero indicates a dot.

The definition for a Center linetype thus indicates that it consists of a line 2.5 units long followed by a space of 0.5 units, then a line of 0.5 units, and a space of 0.5 units. The pattern repeats automatically to fill the allocated total line length, so that although the file defines only two lines and two spaces, a center line looks like this:

—- - ——- - ——- - ——- - ——- - —-