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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. .
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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