Section Views Chapter 12

Section Views Used to describe interior details of a part that cannot be seen in an orthographic view Eliminates the need to dimension hidden lines Better describes the shape than hidden lines Easier to understand

Cutting plane lines Shows the location of the section view (where the part has been cut) Can be multiple line types

Simplified cutting plane

Arrowheads Indicate the direction of sight Points toward the area to be described in the section view Most common mistake is to point arrows the wrong direction

Crosshatching (Section lines) Used to show the material that has been cut by the cutting plane line

Guidelines for crosshatching Typically drawn at 45˚ 30˚ and 60˚ also common Any angle between 15˚ and 75˚ is acceptable Cannot be parallel or perpendicular to any object lines Must be evenly spaced Spacing must ensure that it’s understood to be crosshatching

Common hatching mistakes

Crosshatching styles (coded section lines) Can be used to represent specific materials Not commonly used on engineering drawings

Section views of thin parts If part is too thin to see hatching thin parts are commonly filled

Types of section views Full Sections Cutting plane line extends completely through the part Usually through the center of the part or a feature on the part

Half Sections The section view is half sectioned and half orthographic view Used on symmetrical parts

Offset Sections Cutting plane line is staggered to pass through multiple features that are not on the same plane View is drawn as if all features are on the same plane

Aligned Sections Cutting plane line is staggered to pass through offset features Section views drawn as if the cutting plane is rotated to the plane perpendicular to the line of sight

Unsectioned Features Some features that appear on the cutting plane are left without crosshatching Bolts Nuts Rivets Screws Springs Shafts Bearings Gear teeth Pins Keys Ribs Webs Spokes Can be difficult on 3D CAD

Conventional Revolutions For symmetrical objects Practice of revolving features to the cutting plane of the section view of a symmetrical part All symmetrical features revolved to the cutting plane Showing these features in true projection would result in confusion Difficult to do with CAD Drawing data is tied to 3D models, so it can be hard to follow this practice

Broken-out Sections Small area of a standard orthographic view is removed to show details behind it No cutting plane line Hard to tell the location of the section

Auxiliary Sections Section view that appears as an auxiliary view

Using Section Views in place of orthographic views Acceptable to replace orthographic views with section views Must make sure that no details of the part are omitted by removing an orthographic view

Conventional Breaks Used to show a part that is a constant shape for a long length Makes the view shorter/take up less space 2 methods of showing breaks

Revolved Sections Section view is revolved 90˚ about a centerline on an orthographic view Superimposed on view Can be broken away or not

Removed Sections Similar to revolved except they are removed from the orthographic view

Labeling section views Necessary when there is more than one section view on a drawing or the scale of the section view differs from that of the drawing Views are labeled alphabetically Letters are placed at the ends of the cutting plane line or arrows Large text: .2-.25 tall

View labels Labels placed under section views SECTION A-A (large text) Letters not used: I, O, Q, S, Z (look like numbers)

Arrangement of drawing views Section views should be arranged in order that they are labeled (alphabetically) Makes them easier to find