Lineweights add width to your objects, both on screen and on paper. Using lineweights, you can create heavy and thin lines to show cuts in sections, depth in elevations, dimension lines and tick marks, and varying object thicknesses in details. By assigning varying lineweights to different layers, you can easily differentiate between new, existing, and demolition construction. Just as heavy and thin lead weights are used in manual drafting, lineweights can be used to graphically represent different objects and types of information. You should not use lineweights, however, to represent the exact width of an object. For example, if you want to draw an object with a real-world width of 0.5 inches, you should not use a lineweight; instead, use a polyline with a width of 0.5 inches to represent the object accurately.
Objects with a lineweight plot with the exact width of the assigned lineweight value. Lineweight values consist of standard settings including BYLAYER, BYBLOCK, and DEFAULT. Values are displayed in either inches or millimeters, with millimeters being the default. DEFAULT is the default value for layers. For information on the DEFAULT lineweight value, see “Using the Default Lineweight.” A lineweight value of 0 is displayed as one pixel in model space and plots at the thinnest lineweight available on the specified plotting device. Any object with a lineweight of 0.01 inches (0.025 mm) or less is displayed with a width of one pixel in model space. Lineweight values that you enter on the command line are rounded to the nearest predefined value.
You can export drawings to other applications or cut objects to the Clipboard and retain lineweight information. You can also set the lineweight units and the default value in the Lineweight Settings dialog box. You can access the Lineweight Settings dialog box by using the LWEIGHT command, right-clicking the LWT button on the status bar and choosing Settings, or choosing Lineweight Settings on the Display tab in the Options dialog box.
NOTE If you save an AutoCAD drawing in the format for a previous release, the drawing preview displays lineweights even though the pre-AutoCAD 2000 drawing does not display lineweights.
System variables LWUNITS sets the units in which lineweight is displayed and applied to newly created objects and layers, millimeters or inches. LWDEFAULT sets the default value of DEFAULT for lineweights.
The following table shows the valid lineweight values used in AutoCAD (not including the values of BYLAYER, BYBLOCK, DEFAULT, and 0) as well as associated industry standards. You can also customize lineweights to plot at whatever value you want by using the Plot Style Table Editor.