From FreeCAD Documentation
- There are several ways to invoke the tool:
- Press the Subtractive pipe button.
- Select the PartDesign → Create an substractive feature → Subtractive pipe option from the menu.
- In the Select feature dialog, select a sketch to be used as first cross-section and click OK.
- Alternatively, a sketch or a face of a 3D object (introduced in version 0.20) can be selected before starting the tool. You will not get this dialog then.
- In the Pipe parameters under Profile, press the Object button.
- Select the sketch to be used as path in the 3D view:
- Alternatively, edges of the body can be selected by pressing Add Edge and selecting edges in the 3D view.
- To use more than one cross-section, under Section transformation set the Transform mode to Multisection; press Add Section then select a sketch in the 3D view. Repeat for each additional cross-section.
- Set options if needed and click OK.