AutoCAD · Object Editing
Drawing basic shapes in AutoCAD isn’t that difficult. The real challenge comes after. Editing tasks — trimming and extending lines, rounding corners, copying, and rotating objects — make up the majority of actual drafting time.
“From TRIM (TR) to ARRAY (AR) — here’s a complete guide to the object editing commands you’ll use every day.”
In this post, we’ll walk through the most frequently used object editing and modification commands in AutoCAD. Each command comes with its shortcut key and practical tips you can put to use right away.
1. TRIM (Shortcut: TR)
TRIM cuts away unwanted portions of an object where two objects intersect. Whenever lines overshoot or overlap during drafting, type TR and press Enter.
- Basic usage: TR → Enter → select the cutting edge(s) → Enter → click the part you want to trim
- Select-all tip: If selecting cutting edges one by one is tedious, type TR and press Enter twice. AutoCAD then treats all objects in the drawing as cutting edges, so you can simply click whatever you want to trim. This is by far the most common approach in practice.
While TRIM is active, hold Shift and click to temporarily switch to EXTEND. Conversely, while EXTEND is active, holding Shift switches to TRIM. Since these two commands are often used back-to-back, knowing this toggle will noticeably speed up your workflow.
2. EXTEND (Shortcut: EX)
EXTEND stretches a line, arc, or other object until it meets a specified boundary. Think of it as the exact opposite of TRIM.
- Basic usage: EX → Enter → select the boundary edge(s) → Enter → click the end of the object you want to extend
- Just like TRIM, pressing Enter twice selects all objects as boundaries.
3. FILLET (Shortcut: F)
FILLET rounds the corner where two lines meet using a specified radius (R). Rounded corners appear constantly in mechanical drawings, making this one of the most-used commands.
- Basic usage: F → Enter → type R (radius option) → Enter → enter the desired radius value (e.g., 5) → Enter → click the two lines in sequence
- Radius 0 for clean corners: Setting the radius to 0 connects two lines at a sharp corner with no rounding. This is handy when two lines don’t quite meet and you need them to connect precisely.
Once you set a radius value, AutoCAD retains it the next time you run FILLET. If you used R5 on one corner and then want to clean up another corner with R0, you must change the radius back to 0 explicitly. Forgetting this is a surprisingly common trip-up — keep it in mind.
4. CHAMFER (Shortcut: CHA)
Where FILLET creates a rounded corner, CHAMFER cuts the corner at a straight diagonal angle (C value).
- Basic usage: CHA → Enter → type D (distance option) → Enter → enter the first chamfer distance → Enter → enter the second chamfer distance → Enter → click the two lines in sequence
- If both distances are equal, you get a 45° chamfer. Different values produce an asymmetric chamfer.
- Setting both distances to 0 connects two lines at a sharp corner, just like FILLET with R=0.
5. COPY (Shortcut: CO)
COPY duplicates selected objects and places them at a new location, leaving the originals in place.
- Basic usage: CO → Enter → select the objects to copy → Enter → click a base point → click the destination
- A single COPY command lets you place multiple copies in a row. Keep clicking new destinations and press Esc or Enter when done.
6. MOVE (Shortcut: M)
MOVE relocates selected objects to a new position. The workflow is nearly identical to COPY, but the original is removed from its starting location.
- Basic usage: M → Enter → select the objects to move → Enter → click a base point → click the destination
- To move an exact distance, click the base point and then type a relative coordinate (@X,Y).
7. ROTATE (Shortcut: RO)
ROTATE turns selected objects around a base point by a specified angle.
- Basic usage: RO → Enter → select the objects → Enter → click the rotation base point → type the angle (e.g., 90) → Enter
- Angles are counter-clockwise for positive (+) values and clockwise for negative (−) values. To rotate 45° clockwise, enter −45.
- Copy option (C): Type C during the ROTATE command to keep the original in place and create a rotated copy.
8. MIRROR (Shortcut: MI)
MIRROR creates a mirror image of selected objects across a specified axis. When drawing symmetrical parts, you can draw just one half and mirror it — cutting your drafting time significantly.
- Basic usage: MI → Enter → select the objects → Enter → click the first point of the mirror line → click the second point → choose whether to delete the original (Y: delete, N: keep)
When you mirror objects, any text or dimensions in the selection may also flip and become unreadable. The system variable MIRRTEXT controls this behavior.
- MIRRTEXT = 1: Text is mirrored (flipped) along with the geometry (default)
- MIRRTEXT = 0: Text remains readable in its original orientation
In the command line, type MIRRTEXT → Enter → 0 → Enter to apply. This setting persists throughout the drawing session, so it’s best to configure it at the very start of your work.
9. ARRAY (Shortcut: AR)
ARRAY creates multiple copies of an object in a regular pattern. Two types are essential: Rectangular Array and Polar Array.
9-1. Rectangular Array
Distributes objects in a grid defined by rows and columns. Perfect for bolt hole patterns or any geometry that repeats at regular intervals.
- Basic usage: AR → Enter → select the object(s) → Enter → type R (Rectangular)
- Specify the number of rows, number of columns, row spacing, and column spacing.
- After the array is created, you can drag the blue grip handles to visually adjust row/column counts and spacing.
9-2. Polar Array
Arranges objects in a circular pattern around a center point. Commonly used for flange bolt holes, gear teeth, and similar circular patterns.
- Basic usage: AR → Enter → select the object(s) → Enter → type PO (Polar) → click the center point
- Specify the number of items and the fill angle (default is 360°).
- Item rotation: Each copy automatically rotates to face the center. If you want all copies to maintain the original orientation, turn off “Rotate Items” in the ribbon.
In AutoCAD 2012 and later, arrays are associative by default — the entire array is treated as a single group, so you can edit the count, spacing, and other parameters at any time. If you need to work with individual items separately, use EXPLODE (shortcut: X) to break the array apart.
Quick Reference: Editing Commands at a Glance
| Command | Shortcut | Function |
|---|---|---|
| TRIM | TR | Cut away unwanted portions at intersections |
| EXTEND | EX | Stretch an object to meet a boundary |
| FILLET | F | Round a corner with a specified radius (R) |
| CHAMFER | CHA | Cut a corner at a diagonal (C value) |
| COPY | CO | Duplicate objects to a new location |
| MOVE | M | Relocate objects to a new position |
| ROTATE | RO | Rotate objects around a base point |
| MIRROR | MI | Create a mirror image across an axis |
| ARRAY | AR | Duplicate objects in a rectangular or polar pattern |
Wrapping Up
The commands covered in this post are among the most frequently used in any AutoCAD drafting workflow. In particular, mastering three habits will save you a tremendous amount of time on the job: switching between TR and EX with Shift, always double-checking your FILLET radius before applying it, and setting MIRRTEXT to 0 at the start of each session.