Reference geometry (planes, axes, points)
Datum planes, axes and points — the scaffolding sketches, features and mates hang on.
The three base planes get you far, but real parts need scaffolding: a sketch plane above the part, an axis to revolve around, a point to aim a mate at.
Planes
Features ▸ Plane creates a datum plane — most often an offset from a base plane or a flat face (type the distance, flip if needed). Uses:
- loft sections at different heights (Loft)
- a sketch plane floating above the model
- a Mirror plane at the part's midline
Planes are features: edit the offset later and everything sketched on them follows.
Axes
Datum Axis gives revolves, circular patterns and mates an explicit centreline. Handy sources: a cylindrical face's own axis, or the intersection of two planes.
Points
Datum Point marks a position — pattern anchors, a loft's end cap (point cap), or measurement targets. A sketch containing only points is valid on purpose: it's the standard way to lay out hole centres for Holes, threads & coils.
Mate references
In parts destined for assemblies, a Mate Ref pre-names the face/axis a mate should grab, so inserting the part snaps it in with less clicking.
When it fails
- A plane's parent face was consumed by a later feature — the plane dangles; re-pick its reference (Fix a rebuild error).
Related: Sketching basics · Patterns & Mirror