Fillet Polyline

Fillet Polyline

Win32 and 64, English

Breaks all corners of a polyline and connects the sides with a smooth arc. Able to mate arc segments.

General Usage Instructions

As the source data, you can select two lines or arcs. The main thing is that they lie in the same plane and have a common point. You can also select two segments of a polyline (straight or accurate) via Ctrl.
During the selection of objects, you have the following options:
  • Diameter - enter the diameter of the cutter
  • subselect/subselectOFF - enable selection of sub-objects (polyline segments) in order not to hold Ctrl.
  • MillSide / BOthSide - make fillets only from the side of the cutter's path around the contour or fillet all corners.
  • SwitchStyle - Quickly switch the style of the CNC directly in the command line using the style number.
  • Tune - call setup dialog
If the diameter of the cutter is not specified in the settings of the current CNC style, it will be requested. You can set any diameter cutter. The default diameter is 8 mm or half an inch (depending on the drawing units). While entering the diameter, you can also select the Tune option to bring up the settings dialog.
Note that by changing the cutter diameter in this command, you will reconfigure it in the other contour machining commands (Outside Loop and Dado Loop).
If the option "Both sides" is not checked, the program will ask you to choose from which side of the contour the cutter will go - from the outside or from the inside of the contour. You can set this with the help of layers - if the contour is on the NC_Outside layer, then the selection is done from the outside, if NC_Inside, then from the inside.
The program draws an arc with a diameter slightly larger than the cutter (the gap is also adjustable) tangentially to both segments and cuts the segments for the joint with the arc. The program does not know how to lengthen the segments to build a fillet.
If the polyline segment is too short to mate with a fillet arc, then the program will move the arc to the end of this segment.
If the fillet attempt is unsuccessful, the program will try to construct a fillet of the following segments, but it works only for short segments, within the diameter of the cutter.
You can configure the program to skip obtuse angles. Making fillet in angles that are too obtuse does not make sense, since the difference from the original contour may be barely noticeable, a less permissible variation. The program will automatically calculate the most obtuse angle for which it makes sense to do a fillet. For example, for an 8 mm milling cutter and a 0.5 mm error, corners that are duller than 122.1° will be ignored. Skipping obtuse angles is configured in the CNC settings dialog.
The program runs in a loop and will request new polylines until you press Esc.
Watch the command line - all messages of the program are displayed there, in particular the number of angles in which it is impossible to construct a fillet.



Ribbon/Toolbar Icon Command Command Description


Fillet polyline


The installer that ran when you downloaded this app/plug-in from the Autodesk App Store will start installing the app/plug-in. OR, simply double-click the downloaded installer to install the app/plugin. You may need to restart the Autodesk product to activate the app/plug-in. To uninstall this plug-in, exit the Autodesk product if you are currently running it, simply rerun the installer, and select the "Uninstall" button. OR, click Control Panel > Programs > Programs and Features (Windows 7/8.1/10/11) and uninstall as you would any other application from your system.

Additional Information


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If you have an interest in the new version, just download it from the A>V>C> website and unpack it into the same directory with the replacement of all files. Autodesk® AutoCAD® course must be closed.

Updates are free. Reactivation is not required.

Known Issues

  • There are many cases in which it is impossible, in principle, to construct an arc of fillet. The laws of geometry cannot be fooled.
  • Narrow long "guts" into which a given mill does not pass, of course, will not fillet - this is simply impossible. To cut off this piece of contour, select 2 non-adjacent segments at the entrance to the gut (by pressing CTRL) and call FP. The program will try to make an arc between these segments and erase an impassable section of the contour.
  • The program does not attempt to lengthen segments before fillet. If the specified diameter is insufficient to reach from the end of one segment to the beginning of the second, then the fillet will not be built.
  • The program does not check the contour for bottlenecks. Perhaps there will be areas where the mill just does not fit. Check the resulting circuit using the _Offset command.
  • It is noticed that sometimes the _Offset command cannot process a polyline built by a program. This sometimes happens when the Offset must absorb one of the fillet arcs. Try slightly increasing the radius of the arcs (just pull the middle point to the ends of the arc) - this helps.


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Author/Company Information


Support Information

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Version History

Version Number Version Description


AutoCAD 2025 compatibility


All updates on 2023 October


Added 2024 support.


Added 2022 support (No change in version number).


- Compatible with AutoCAD 2021 - Cumulative updates


Compatible with AutoCAD 2020 New activation system


Initial release
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