Sectional Views in Engineering Graphics

Sectional Views

• Orthographic views showing all hidden lines may not be clear enough to describe an object's internal details.
• Section views are used to overcome this shortcoming by imagining that part of the object has been cut away and shown in a cross-sectional view.
• The cut line is called a "cutting plane", and can be done in several ways.

Section Lining

• Lines should never be parallel or perpendicular to the object lines.
• If the outline of the object has 45° lines, 30° or 60° lines should be used.
• Assemblies with several parts should be lined with varying angle section lines.

Section Lining - Line Placement Breaks

• ANSI Standard Section Lines for Various Materials are set by the American National Standards Institute Mechanical and Aerospace Engineering Dept., SJSU.

Types of Section Views

• 1. Full section view: the cutting plane line passes fully through the part, and the section-lined areas are those portions that have been in actual contact with the cutting-plane.
• 2. Half section view: used for symmetrical objects, the cutting-plane line cuts halfway through the part and removes one quarter of the material.
• 3. Offset section view: used to show parts and features that do not line up with each other, the cutting-plane line does not travel in a straight line.
• 4. Aligned section view: usually used on symmetrical circular parts, the cutting-plane line is placed to show the most detail.
• 5. Broken-out section view: removes a small amount of material to show the interior details, used to enhance the orthographic view by giving the viewer a better look at key interior details.

Section View Guidelines

• All visible edges and contours behind the cutting plane should be shown.
• Hidden lines should be omitted in section views.
• A section view should always be bounded by a visible outline.
• There should be no lines in the hatched area.
• Section lines should be in the same direction.