How to Trim Lines in FreeCAD Sketcher

The Trim tool in FreeCAD's Sketcher workbench allows you to quickly clean up intersecting geometry by cutting line segments back to their nearest intersection points. This guide provides a straightforward, step-by-step walk-through on how to activate the trim tool, select unwanted line segments, and manage sketch constraints to ensure your 2D profiles remain fully defined and ready for 3D modeling operations like padding or revolving.

Step 1: Open Your Sketch

Ensure you are in the Sketcher workbench and actively editing the sketch containing intersecting lines. You can enter sketch edit mode by double-clicking the sketch in the model tree.

Step 2: Activate the Trim Tool

You can activate the trim tool using one of the following methods:

  • Click the Trim an edge icon in the Sketcher toolbar (represented by a pair of scissors cutting a line).
  • Use the keyboard shortcut by pressing T.

Once activated, your cursor will change to indicate that the tool is ready.

Step 3: Select Segments to Remove

  1. Hover your cursor over the specific segment of the intersecting line you wish to remove. FreeCAD will highlight the line segment between the two nearest intersections in yellow or red depending on your theme.
  2. Left-click on the segment. FreeCAD will immediately delete that portion of the line.
  3. The remaining segments will automatically be assigned a coincident constraint at the intersection point to maintain the connection.

Step 4: Continue Trimming or Exit

  • Continue: Click on any other unwanted overlapping or intersecting lines directly; there is no need to reselect the tool for each cut.
  • Exit: Once the geometry is clean, right-click the workspace or press the Esc key to exit the trim tool.

Best Practices for Trimming in FreeCAD

  • Preserve Intent: Always click directly on the segment you want to discard, not the part you want to keep. The tool removes the segment beneath your cursor up to the adjacent boundaries.
  • Watch Constraints: Trimming removes original endpoints and adds new coincident constraints. This can occasionally cause "redundant constraint" warnings in the Solver Messages panel. If this occurs, click the blue auto-remove link in the Tasks tab or manually delete the redundant constraints.
  • Trimming Full Circles: If you trim a closed circle that intersects other geometry, FreeCAD converts it into an arc bounded by the intersection points.