Today AutoCAD Tutorial: How to set dimension extension lines to an equal length in AutoCAD?
You can see between above two indicated images. There are two ways to set dimension extension lines to an equal length.
Method 1: Setting Fixed length extension lines feature in Modify Dimension Style dialog box
1. At command line: D > Enter, AutoCAD wil display Dimension Style Manager. You select Dimension Style > Modify. Modify Dimension Style dialog box is showed.
2. Select Lines tab.
3. At Lines tab, tick on Fixed length extension lines > input fixed length. For example: it is 10.
Method 2: Using AutoCAD Lisp to cut extension lines
About using this Lisp, you can refer “Download AutoCAD Lisp cut Extension lines“.