Auxiliary and Detail Views

Extra views make sloping surfaces and small features easier to read

An auxiliary view is an extra drawing view that looks straight at a flat, sloping surface so its shape is clear. A tilted rectangular surface can look shortened from above; looking straight at it reveals its rectangular proportions.

A detail view is an enlarged picture of a selected small region, such as a hole with crowded edges or dimensions. The actual part stays the same size. Use an auxiliary when the viewing direction makes the shape hard to read, and a detail when a small region needs more room.

A view's scale tells you how large its picture is compared with the real part. Read the view labels and scale information to connect an added view to the original drawing. To expose an interior hidden behind solid material, use a section view.

Look perpendicular to a face to see its true shape

A face is a surface on the part. Look straight at a flat face, perpendicular to it, to see its true shape. In projection terms, that face is parallel to the imaginary flat surface on which the view is drawn: the projection plane.

In the figure, the part is a wedge with a flat, sloping rectangular face. The front view sees that face edge-on, so the face is reduced to the line P–Q. The light-blue rectangle is the same face viewed straight on in the auxiliary view.

In this example, the front view sees the inclined face on edge. The top view shows it foreshortened: its sloping length appears shorter because the view is not looking straight at the face. The top view's 160-unit length is not the face's true 200-unit length.

Scale is the ratio of a length on the drawing to its actual length. “True shape” still allows the stated drawing scale; it does not mean the image must be life size. The auxiliary view shows the face's correct proportions without the shortening caused by the viewing direction.

A primary auxiliary view is constructed directly from a principal view, such as the front, top, or side. Choose its projection plane parallel to the inclined face. Review Orthographic Projection and the Glass Box and Choosing Drawing Views for the principal views.

A detail enlarges a feature; a break shortens the view

The existing view from which a detail is taken is its parent view. A boundary and letter usually identify the selected region. In the figure, the circle marked B locates the region shown in Detail B.

Match the detail label and read its scale. 2:1 means a drawn length is twice the actual length; the hole itself has not grown. Enlargement alone does not change the viewing direction or reveal hidden features.

A broken view omits a middle length of a long, substantially uniform part so its ends and features fit on the sheet. Break lines identify the omission. The actual part remains continuous, and dimensions across the break state its full size. Use those dimensions rather than measuring the shortened illustration.

A broken view is different from a broken-out section, which shows interior geometry by representing a local portion of material as removed. See Section Views.

Project from the edge view and transfer the missing depth

The auxiliary figure above uses the front view as its parent. Its thin projectors are construction lines used to line up corresponding points in the two views.

1. Find the principal view in which the face is a line. In the example, the front view shows the sloping face edge P–Q.
2. Draw a fold or reference line parallel to P–Q. It represents the hinge between the parent and auxiliary projection planes.
3. Draw thin projectors perpendicular to the fold line from the face’s corners.
4. Transfer each corner’s depth from the corresponding principal view, using the same reference and drawing scale. Here the top view supplies a constant depth of 80.
5. Connect corresponding points. The face is a 200-by-80 rectangle in the auxiliary view, although the top view shows its sloping length shortened to 160.

These are invented drawing units for the construction. The projectors and fold line are not physical edges on the part. The auxiliary view shows this face's true shape, not necessarily the true shape of every other face.

Use a partial auxiliary view when only one face matters

A partial auxiliary view shows the useful inclined face and enough nearby geometry to identify it. Omit unrelated geometry that would make the view crowded, using an appropriate break boundary where the view is interrupted.

Keep the viewing reference, label, and scale clear. Partial means limited coverage; it does not change the projection direction. The construction above isolates the inclined face for that reason.

Create auxiliary, detail, and break views from the parent in CAD

Auxiliary view

Select the parent and a reference edge representing the inclined face edge-on. Use Auxiliary View in SOLIDWORKS or Auxiliary view in Onshape, check the direction, and place the view. For a partial view, limit the displayed region with the application’s crop or partial-view controls while retaining identifying references.

Detail view

Use Detail View in SOLIDWORKS or Detail view in Onshape. Define the region, place the enlarged view, and set its scale and label. Verify that dimensions reference the intended model edges.

Broken view

Use Break View in SOLIDWORKS or Break view in Onshape. Choose break direction and style, then position the two break boundaries. Check that no feature needed to define the part was omitted.

Review the result after every model revision. A generated view can be geometrically valid yet omit the feature the reader needs.

Practice choosing the true-shape view Practice reading a broken view