How to Fillet in AutoCAD: Step-by-Step Guide

In AutoCAD, use the FILLET command to create a rounded corner between two lines or objects by specifying a radius. Type FILLET, set the radius if needed, select the two objects, and AutoCAD will draw the arc connecting them smoothly.

Syntax

The basic syntax for the fillet command in AutoCAD is:

• FILLET - Starts the fillet command.
• Radius - Sets the radius of the arc that will connect the two objects.
• Select Object 1 - Choose the first line or object.
• Select Object 2 - Choose the second line or object to fillet with the first.

You can also use options like Trim to control whether the original lines are trimmed to the fillet arc.

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FILLET
Radius
Select Object 1
Select Object 2

Example

This example shows how to fillet two lines with a radius of 5 units:

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Command: FILLET
Current settings: Trim = On, Radius = 0.0000
Specify fillet radius <0.0000>: 5
Select first object: (select line 1)
Select second object: (select line 2)

Output

AutoCAD creates a smooth arc of radius 5 units connecting the two selected lines, trimming them to the arc edges.

Common Pitfalls

Common mistakes when using fillet in AutoCAD include:

• Not setting the radius before selecting objects, which defaults to 0 and creates a sharp corner.
• Selecting objects that do not intersect or are too far apart, causing no fillet to be created.
• Forgetting to set Trim option, which may leave original lines untrimmed and cause overlapping geometry.

Always check the radius and trim settings before applying fillet.

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Command: FILLET
Specify fillet radius <0.0000>: 0
Select first object: (select line 1)
Select second object: (select line 2)

// Result: No arc created, lines remain sharp.

// Correct way:
Command: FILLET
Specify fillet radius <0.0000>: 3
Select first object: (select line 1)
Select second object: (select line 2)
// Result: Rounded corner with radius 3 created.

Quick Reference

Command	Description
FILLET	Starts the fillet command to round corners
Radius	Sets the radius of the fillet arc
Trim	Option to trim original lines to the fillet arc (On/Off)
Select Object 1	First line or object to fillet
Select Object 2	Second line or object to fillet

Key Takeaways

Use the FILLET command to create smooth rounded corners between two lines or objects.

Always set the fillet radius before selecting objects to control the curve size.

Check the Trim option to decide if original lines should be trimmed to the fillet arc.

Fillet only works if the two objects are close enough or intersecting.

Practice selecting objects carefully to avoid no fillet or unexpected results.