Can I round all four corners of a rectangle at the same time in AutoCAD?
Short Answer
Yes — in AutoCAD, you can round all four corners of a rectangle at once by using the FILLET command with the Polyline option on a rectangular polyline. This is the fastest and most common professional method for creating uniform rounded corners. It only works correctly if the rectangle is a single polyline.
What You Need to Know Before
Warning: If your rectangle was created as separate lines instead of one closed polyline, AutoCAD will not round all four corners in one action with the Polyline option. Also, if the fillet radius is too large for the rectangle size, the operation can fail or distort the shape.
How to Round All Four Corners of a Rectangle at the same time
- Command: FILLET
- Shortcut: F
- Quick Steps:
- On the Ribbon, go to Home > Modify panel > Fillet, or type F and press Enter.
- Type R to set the Radius, enter the required value, then press Enter.
- Type P for Polyline, then select the rectangular polyline to round all four corners at once.
Variables & Settings
- Key Setting: Radius in the FILLET command
- Expert Setting: The fillet radius stays active for the next fillet operations until you change it. If the radius is larger than half the rectangle’s shortest side, the rounded corners may fail or produce unexpected geometry.
Why it Fails
- Cause 1 (Geometry): The rectangle is not a closed polyline, so the Polyline fillet option cannot process all four corners in one step.
- Cause 2 (layers/Locks): The rectangle is on a locked layer, preventing AutoCAD from modifying the object.
- Cause 3 (Command/Logic): The fillet radius is too large for the rectangle dimensions, so AutoCAD cannot create valid tangent arcs at all corners.
Quick Fix & Best Practice
- Quick Fix: Use PEDIT > Join to convert separate lines into one closed polyline, then run FILLET with the Polyline option again.
- Manager’s Verdict: Use this method for standard 2D production work when you need equal corner radii fast. Avoid it if each corner needs a different radius.
FAQ
Can I fillet a rectangle made from four separate lines?
Yes, but not all four at once until you join them into one polyline.
Can I use different radii on each corner?
No, not with the Polyline fillet option; you must fillet corners individually.
Does this work on 3D solids?
No, this method applies to 2D rectangles or closed polylines, not 3d solid edge fillets.
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