Section Views

Use an imaginary cut to expose the interior

A section view shows what is inside a part without making you untangle a group of hidden lines. Imagine cutting the part, removing the material between you and the cutting plane, and looking at what remains.

The cut changes the drawing representation, not the manufactured part. Hatch the material crossed by the plane and show the useful visible edges beyond it. Hidden lines are usually omitted in sections unless needed to make the shape clear.

Start with The Alphabet of Lines and Orthographic Projection and the Glass Box if the line types or viewing directions are unfamiliar. For a sloping face or a small feature, see Auxiliary and Detail Views.

Full sections cut all the way through the part

A full section uses one plane through the entire part. For this hollow cylinder, a plane through the axis exposes both walls and the bore. The bore is empty space and receives no hatching.

Half sections combine the exterior and interior

A half section is useful for a symmetric part. Imagine removing one quarter with two perpendicular cutting planes. The resulting view shows one half in section and the other half as an exterior view, usually divided by a center line.

It is not a full section with half its hatch erased. The unsectioned half shows the outside, and symmetry supplies the connection between the two halves.

Offset sections reach features that are not in one straight line

An offset section jogs the cutting plane to pass through several features. Project the selected parallel portions into one section. The jogs help explain the cut location; they do not create physical edges on the part.

Read the parent view for the holes’ actual locations. Their appearance together in the section does not mean they lie in one straight row.

Broken-out sections expose only a local area

A broken-out section removes a limited patch to a chosen depth in an existing view. An irregular break line marks the boundary. Use it to expose a small passage or wall without adding a complete section view.

A separate cutting-plane line is normally unnecessary: the local boundary identifies the area. Depth still matters; a cut that stops before a bore will not reveal it. This differs from a broken view, which merely shortens a long part on the sheet.

Revolved sections show a cross section in place

A revolved section turns a cross-sectional slice 90° into the plane of the drawing and places it on the parent view. It is useful for the shape of a bar, spoke, or arm. Show the slice itself, rather than the features behind the cut.

Removed sections place the slice clear of the parent view

A removed section places the cross section away from the parent view to keep it readable. Match its identifying letters to the cutting plane. Several removed sections can describe changes along a long part; keep each location unambiguous.

Aligned sections rotate an angled portion into the section plane

An aligned section uses intersecting cutting planes through features arranged around an axis. An angled portion is rotated into alignment before it is shown in the section. This makes radial features easier to read.

Do not infer angular spacing from the aligned result. In this disk, one small hole is rotated into the section plane; its original angular position is established by the top view.

Hatch cut material, with conventional exceptions

Use thin, evenly spaced diagonal lines, commonly near 45° to the main outline. Change the angle when the hatch would be confused with an edge. Keep a part’s hatch consistent; distinguish adjacent assembly parts by changing hatch angle or spacing.

• Voids: holes and open spaces are never hatched as solid material.
• Ribs, webs, and spokes: a cut along their length generally leaves them unhatched so they do not look like a thick solid wall. A transverse cut through their thickness is hatched.
• Shafts and fasteners in assembly sections: when cut lengthwise through their axes, solid shafts, bolts, nuts, washers, pins, and similar standard parts are commonly shown unsectioned. A transverse shaft section can be hatched; “never hatch a shaft” is too broad.

An unhatched region may be empty space, an uncut surface, or a conventionally unsectioned component. Use its outline and the other views to decide which.