FreeCAD

DXF sketches

1. File › Import and choose the DXF.
2. The geometry arrives as Draft objects. To work with it in Part Design, select it and use the Draft workbench’s Draft to Sketch.

If arcs or splines come in wrong, check the DXF importer settings in Preferences › Import-Export › DXF, or make the DXF with Curves › Polylines in ShapeMason.

STEP solids

File › Open (a new document) or File › Import (into the open one) and choose the .step. Each solid is a Part feature you can use in Part Design as a base feature, or in booleans.

Recipes

You want	Use case
A supplier’s DXF that extrudes	Clean it first
A mesh as an editable body	Mesh to solid, tuning noisy meshes
A plate or bracket from a 2D drawing	Mounting plate with real holes