How to Do a Boolean Cut in FreeCAD Part Workbench

This guide explains how to perform a Boolean cut (subtraction) operation using the Part workbench in FreeCAD. You will learn the correct workflow for selecting your base and cutting shapes, executing the cut tool, managing the resulting parametric feature in the tree view, and avoiding common geometry errors associated with Boolean operations.

Step 1: Switch to the Part Workbench

  1. Open your model in FreeCAD.
  2. Locate the workbench drop-down menu in the top toolbar (often defaulting to "Start" or "Part Design").
  3. Select Part from the list.

Step 2: Prepare Your Shapes

Ensure you have two intersecting 3D solid objects ready in your 3D view.

  • Base Object: The solid you want to keep.
  • Cutting Tool: The solid you want to subtract from the base object.

Both objects must be valid solids (manifold geometry) rather than open shells or meshes.

Step 3: Select the Objects in Order

Selection order is critical in FreeCAD Boolean operations:

  1. In the Tree view (or directly in the 3D viewport), click the Base Object first.
  2. Hold down the Ctrl key (or Cmd on macOS).
  3. Click the Cutting Tool second.

If you select them in reverse order, the wrong part of the model will be removed.

Step 4: Execute the Cut

  1. Locate the toolbar icon showing two overlapping shapes where one is subtracted (a blue sphere with a white cylinder cut out).
  2. Click the Make a cut of two shapes button (or navigate via the menu bar: Part > Boolean > Cut).

The cutting shape will disappear, leaving a cavity or subtracted geometry in the base object.

Step 5: Modify or Inspect the Cut

In the Tree view, your two original objects are now grouped under a single parametric feature named Cut.

  • Click the arrow next to Cut to expand it and reveal the original base and tool shapes.
  • To adjust the position or size of either shape, select it within the expanded tree and modify its Placement or dimensional properties in the Property View. The Cut will automatically update.
  • If you selected the objects in the wrong order, select the Cut object in the Tree view, look in the Data tab under Cut, and swap the Base and Tool properties.

Common Troubleshooting Tips

  • Coplanar Faces: If the face of the cutting tool aligns perfectly with the face of the base object, the underlying geometry kernel (OpenCASCADE) may fail or produce an invalid shape. Extend the cutting shape slightly beyond the boundary of the base shape to create a clean, unambiguous intersection.
  • Non-Solids: If the cut fails or produces an invisible result, verify that both shapes are solid bodies by checking their Shape Type in the Data tab.