CHAPTER 8

Multiviews

Learning Objectives • • • • Select appropriate views for presentation Prepare single- and multiview drawings Create detail views Draw view enlargements

Learning Objectives • • • Establish runouts Explain the difference between first and third-angle projection Create multiview drawings using first and third-angle projection • Prepare formal multiview drawings from an engineer’s sketch and actual industry layouts

Orthographic Projection • • • System for drawing and dimensioning complex three-dimensional items Changes physical objects and three dimensional ideas into two-dimensional drawings Uses descriptive geometry

Orthographic Projection • • • • Lines of sight perpendicular to plane of projection Surface of the object parallel to the plane of projection: • Surface appears true size and shape Surface of the object not parallel to the plane of projection: • Surface appears foreshortened, or shorter than true length True geometry view

Orthographic Projection

Multiviews • • Multiview projection Multiview drawing • • The result of multiview projection Represents the shape description of the object

Multiview Standards • • ASME • ASME Y14.3, Multi and Sectional View Drawings ISO • Alternate view definition systems

The Glass Box Visualization Method • • Sides of the glass box are planes of projection Six total sides, or views: • • • • • • FRONT TOP RIGHT-SIDE LEFT-SIDE BOTTOM REAR

The Glass Box Visualization Method • Sides unfold at hinge lines, also known as: • • Fold lines Reference lines

The Glass Box Visualization Method • • Arranges views in third-angle projection Projection techniques: • • • 45 ° mitre line Arcs Transfer

Third-Angle Projection • • • Primary multiview projection method Common in the United States Identified by the third-angle projection symbol • Angle of projection block near the title block

First-Angle Projection • • Common in countries other than the United States Identified by the first-angle projection symbol • Angle of projection block near the title block

Third-Angle versus First-Angle Projection

View Selection • Six views possible: • • • • • • FRONT TOP RIGHT-SIDE LEFT-SIDE BOTTOM REAR

View Selection • • • Seldom necessary to use all six views • Only draw the number of views necessary to completely described the object Front view usually most important • Establishes other views Always one dimension common between adjacent views

Selecting the Front View • • • • • Represent the most natural position of use Provide the best shape description or most characteristic contours Have the longest dimension Have the fewest hidden features Be the most stable and natural position

Selecting the Front View

Selecting Two or Three Views • • • • Most contours Longest side Least hidden features Best balance or position

Two-View Drawings

One-View Drawings • • • Thickness identified in a note or title block All shape and dimensional information in one view If in doubt, drawn the adjacent view

Partial Views • • • Symmetrical objects drawn in limited space Simplify complex views Break lines show that a portion of the view is omitted

Detail View • • Increases the scale of part of a view Use when detail cannot be clearly dimensioned due to: • • Drawing scale Complexity

Removed Views • • • Out of normal arrangement with other views Avoid when possible, but may be necessary when: • • Limited space Enlarge the view Can appear on a different sheet from where the view is taken if necessary

Viewing Plane Lines for Removed Views

Arrow Method for Removed Views

Views with Related Parts

Rotated Views • • • Rotated from normal alignment with other views Avoid when possible, but may be necessary when: • Limited space • • Enlarge the view Keep all views on one sheet Angle and direction of rotation under the view title • ROTATED 90 ° CW • ROTATED 90 ° CCW

Projecting Chamfers • Slanted edge or a line

Projecting Circles • • Line of sight perpendicular to a circular feature • Feature appears round Circle projected onto an inclined surface • View is elliptical in shape

Projecting Arcs

Projecting Rounded Corners • Represented as a contour only • • • Fillets Rounds Break corners

Projecting Rounded Curves and Cylindrical Shapes • Phantom lines sometimes used to accent rounded feature

Runouts

Line Precedence • • • Object lines take precedence over hidden lines and centerlines Hidden lines take precedence over centerlines Cutting-plane lines take precedence over centerlines

Line Precedence