Fixed hole detection for bottom faces.

src/Mod/Path/PathScripts/PathUtils.py

@@ -166,7 +166,12 @@ def isDrillable(obj, candidate, tooldiameter=None, includePartials=False):
                                     drillable = True
             elif type(face.Surface) == Part.Plane and PathGeom.pointsCoincide(face.Surface.Axis, FreeCAD.Vector(0,0,1)):
                 if len(face.Edges) == 1 and type(face.Edges[0].Curve) == Part.Circle:
-                    return True
+                    center = face.Edges[0].Curve.Center
+                    if obj.isInside(center, 1e-6, False):
+                        if tooldiameter is not None:
+                            drillable = face.Edges[0].Curve.Radius >= tooldiameter/2
+                        else:
+                            drillable = True
         else:
             for edge in candidate.Edges:
                 if isinstance(edge.Curve, Part.Circle) and (includePartials or edge.isClosed()):