Curved Surfaces and Centerlines

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# Curved Surfaces and Centerlines - PowerPoint PPT Presentation

Curved Surfaces and Centerlines . Sections 11.02 and 10.07 of Text . Objectives . Understand how curved surfaces will appear in each viewing plane. Create orthographic projections of objects with curved surfaces. Correctly use center marks and center lines to add clarity to drawings. .

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### Curved Surfaces and Centerlines

Sections 11.02 and 10.07 of Text

Objectives
• Understand how curved surfaces will appear in each viewing plane.
• Create orthographic projections of objects with curved surfaces.
• Correctly use center marks and center lines to add clarity to drawings.
Curved Surfaces in orthographic
• Similarly to the way inclined surfaces appear as an inclined edge in one view, curved surfaces will appear as a curved edge in one view and as a plane in the two remaining views.
Orthographic Projection of a Cylinder
• The figure below shows an orthographic projection of a cylinder
• Centerlines and centermarks are used to denote the center of a circular or cylindrical feature.

Centerlines

Visible extents of cylinder

Centermark

Circular end of Cylinder

CLICK

Centerlines
• In order to help others understand your drawings, it is necessary to include centerlines and centermarks.
• A centerline alerts readers that the edges next to the centerline may be optical limits of a curved surface and not true sharp edges.
• This case occurs every time a curved surface is shown as a plane.
• The most common occurrence of a curved surface in engineering drawings is a hole with hidden and center lines.
Centerlines
• Centerlines are drawn by alternating long and short dashes along the length of the center of the cylinder or a circular hole.
Centermarks

Hidden

lines

• Centermarks show the center of a circular feature.

This arc is 180°

• Centerline and centermarks are used where the arc of a surface is 180° or greater.
• Note that both centerlines and centermarks extend past the extents of the circle or circular feature.

Center line

Centermark

This arc is 90°

Centermark, note the extension lines

Visible limit of arc

Hidden lines

Center line

Hidden

lines

Center lines

Line Precedence
• Visible lines takes precedence over all other lines
• Hidden lines take precedence over center lines
• Center lines have lowest precedence
• In this drawing, a visible line overlies a centermark.
• Notice that the extension lines from the centermark are still visible.
Curved Surfaces and Centerlines
• Use this time to practice making orthographic projections from objects with curved surfaces.
• Do not forget to include centerlines and centermarks as needed!
• In class assignment