Tip 1005: A new way of looking at three AutoCAD trim command tools

There is nothing either good or bad, but thinking makes it so.
–William Shakespeare (1564–1616), Hamlet. Act ii. Sc. 2

Here is a tip that will make one of the most common CAD tasks, trimming two lines, go quicker and easier. Let’s say you have two lines crossing to make an X shape, and you want to trim them to make a v shape. See this diagram.

CAD tip 005

Trimming an X to make a v

How would you make the trim? There are three basic AutoCAD trimming tools you can use: TRIM, FILLET, or CHAMFER.

First, let’s look at the lines closely. The upper half of the X, the part above the crossing point, is the part that will remain after the trim, forming the v shape. The X can be visualized as being made up of four line segments: the two upper ones, which we want to keep, and the two lower segments, which we want to get rid of.

Using simple terms, we could say that the “good” parts of the X are the two segments of the lines which will remain after the trim is completed–the ones we want to keep. The “bad” parts are the segments which will get eliminated, blown away, blasted, vaporized, vanished into nothingness, sent packing–you get the picture.




Now let’s look at the three trimming tools.

TRIM: In this option, you have a four-step process.

  1. Initiate the TRIM command. You can do this either by clicking on the TRIM button or by using hotkeys TR [ENTER]
  2. Select the cutting edges. You can select the two lines of the X, or just skip this step and go to step 3 to select all lines in the drawing.
  3. Hit ENTER or SPACEBAR to tell AutoCAD that you are finished selecting cutting objects. This is the step that many CAD users overlook.
  4. Click on the two “bad” line segments–the ones in the bottom half of the X.

FILLET: Compare that to using the FILLET command. Here you have a two-step process.
Initiate the FILLET command, by clicking the button or typing F [ENTER].

  1. Click on the two “good” line segments–the ones in the top half of the X.
  2. Note that the radius of the fillet must be set to zero for this to work.

CHAMFER: The third option, CHAMFER, is similar to FILLET, except that you need to make sure that the two distances used to make the fillet are both set to zero. Using CHAMFER has two steps:

  1. Initiate the CHAMFER command, by clicking the button or typing CH [ENTER].
  2. Click on the two “good” line segments–the ones in the top half of the X.

The key thing to remember is this: With the TRIM command, you click on the “bad” parts, but with the FILLET or CHAMFER commands, you click on the “good” parts. This makes it easy to keep the three trimming procedures straight.

Notice that the FILLET and CHAMFER tools only require two steps, half as many as the TRIM tool. Of the three, FILLET is the quickest option in most cases.

Remember also that you can use a right-to-left crossing selection window to select multiple “bad” segments with one stroke. Nothing ugly about that.

Post your comments and responses–I enjoy hearing from you!

Keep on CADDing,


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