The CHAMFER command in AutoCAD bevels a corner, and its alias is CHA. It replaces the apex of a corner with a straight line, and Autodesk describes it as "Bevels or chamfers the edges of two 2D objects or the adjacent faces of a 3D solid".
The command is easy to call, but a few things about it cost people time and rarely appear in tutorials. The order in which you pick the two lines changes the result, the distances are remembered between calls, and one mode leaves whiskers at the corner. To learn modelling and documentation end to end, see the AutoCAD for construction course.
The CHAMFER command in AutoCAD: prompts and seven options
The button sits in the flyout beside the Fillet button on the Modify panel. Typing CHA is quicker.
The command's first line always reports the distances in force, and only then asks for the first line. The three lines read as follows.
| What the command line prints | What it is saying |
|---|---|
(TRIM mode) Current chamfer Dist1 = 0.0000, Dist2 = 0.0000 | Trimming is on, and both remembered chamfer distances are zero |
Select first line or [Undo/Polyline/Distance/Angle/Trim/mEthod/Multiple]: | Pick the first line, or type one of the capitalised letters to take an option |
Select second line or shift-select to apply corner or [Distance/Angle/Method]: | Pick the second line. Holding Shift here applies a zero chamfer just this once |
The seven options and what each is for:
| Option | What it does |
|---|---|
Undo | Reverses the previous action without leaving the command |
Polyline | Chamfers every vertex of a 2D polyline where two straight segments meet |
Distance | Sets the two chamfer distances, measured from the intersection along each object |
Angle | Sets a distance on the first object and an angle measured from it |
Trim | Controls whether the two lines are trimmed to meet the ends of the chamfer |
mEthod | Chooses whether the chamfer is worked out from two distances or from a distance and an angle |
Multiple | Chamfers several corners without recalling the command |
Autodesk's CHAMFER page documents all seven.
The command is not limited to two-dimensional linework. Autodesk's own description mentions "the adjacent faces of a 3D solid", meaning it will bevel the edge between two neighbouring faces of a solid. Calling it works the same way, except that you pick an edge of the solid rather than two straight lines, and the command asks which face is the base surface.
Chamfer distances, or a distance and an angle
This is where the method forks, and picking the right branch saves a good deal of arithmetic.
Chamfering a wall corner with two distances of 400 goes like this:
- Type
CHAand Enter. TypeDand Enter. - Type
400and Enter. The command asks for the second distance, which defaults to the first, so pressing Enter accepts it. - Pick the first line, then the second. The apex is replaced by a bevel.
The other branch works from an angle. Type A and the command asks Specify chamfer length on the first line, then Specify chamfer angle from the first line. Mechanical drawings usually specify bevels this way.
The method in force lives in the CHAMMODE variable. Autodesk records value 0 as "Requires two chamfer distances" and value 1 as "Requires a chamfer length and an angle", of integer type and not saved with the drawing. A new session therefore returns it to 0.
The picking order changes the result
With two equal distances it makes no difference which line you pick first. With two different distances the picking order decides which distance goes on which line, and no Vietnamese tutorial I read mentions it.
The rule fits in one sentence: the first distance applies to the line picked first. If the bevel leans the wrong way, there is no need to change the numbers — pick the two lines in the opposite order.
The distances are also remembered between calls. Set 400 once and every later chamfer uses 400 until it is set again. The command's first line always reports the current pair, so reading that line before picking avoids this whole family of mistakes.
No trim and the TRIMMODE variable
The Trim option controls whether the two lines are cut back. Type T and the command asks Enter Trim mode option [Trim/No trim] <Trim>:.
Choose No trim and the bevel is added while the original lines stay put, leaving a corner with whiskers. The result looks like a failure, but the command did exactly what it was told.
Two things are worth remembering here. First, the setting lives in TRIMMODE, and Autodesk states "The current value is stored in the TRIMMODE system variable". Second, that variable is shared with FILLET. Set No trim in one command and the other stops trimming too, until it is set back.
Chamfering every corner of a polyline
The Polyline option chamfers every vertex of a 2D polyline in a single pick. Type P and click any one of its sides.
There is a condition here that is easy to miss. Autodesk says the command inserts a chamfer at each vertex "where two straight line segments meet" — only at vertices where two straight segments join. A vertex with an arc on one side is skipped.
A rectangle drawn with RECTANG is a polyline, so it works straight away. Four separate lines drawn with LINE do not. Join them with JOIN first, or chamfer each corner using the Multiple option.
Multiple is worth a habit of its own. Without it the command ends after a single corner, so a run of three or four corners means calling it again each time. Type M once at the first prompt and the command keeps asking for another pair of lines until you press Escape.
Five things that spoil a chamfer
Of those five, the last is a technique rather than a hazard. Give both distances as 0 and the command bevels nothing — it brings the two lines together at a single point and trims what sticks out. This is the quickest way to close up a wall corner where two lines do not quite meet.
There is a shortcut for it that leaves your numbers alone. The second prompt reads shift-select to apply corner, meaning that holding Shift while picking the second line applies a zero chamfer just for that one corner, whatever distances are set.
How chamfer and fillet differ
The two commands are siblings, sharing a flyout and with nearly identical prompts.
CHAMFER | FILLET | |
|---|---|---|
| Alias | CHA | F |
| Replaces the apex with | A straight line | An arc |
| Defined by | Two distances, or a distance and an angle | One radius |
| Trim setting stored in | TRIMMODE | TRIMMODE, the same one |
| A value of zero | Squares the corner | Squares the corner |
Autodesk describes FILLET as "Rounds or fillets the edges of two 2D objects or the adjacent faces of a 3D solid", and notes that "A radius value of zero can be used to create a sharp corner". See the FILLET page and Commands for Creating Fillets and Chamfers.
Which one to use is a drafting convention rather than a matter of right and wrong. Step nosings, plinth edges and stair nosings in a building set are usually bevelled, while planter corners, slab edges and cast details are rounded.
One habit helps when a drawing needs both. The two commands share TRIMMODE, so the trim setting need only be set once; but the chamfer distances and the fillet radius are remembered separately, and setting one leaves the other alone.
Frequently asked questions
Which command bevels a corner in AutoCAD?
CHAMFER, aliased CHA. The button sits in the flyout beside the Fillet button on the Modify panel.
My chamfer leans the wrong way. How do I fix it?
Pick the two lines in the opposite order. The first distance always applies to the line picked first, so the numbers need no changing.
Why are both original lines still there after chamfering?
The command is in No trim mode. Type T and choose Trim to restore it. The setting lives in the TRIMMODE variable.
How do I chamfer all four corners of a rectangle at once?
Type CHA, then P, then click any side. The shape must be a polyline; four separate lines need joining with JOIN first.
What is a zero chamfer for?
For squaring a corner. The two lines are brought to meet at a single point and the overhang is trimmed. Holding Shift while picking the second line does the same thing.
How does the CHAMFER command differ from FILLET?
CHAMFER replaces the apex with a straight line and is defined by two distances; FILLET replaces it with an arc and is defined by a radius.
Related articles
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- What is AutoCAD — a handbook for people working in construction