Section 2 Drafting Techniques and Skills Chapter 8 Multiview Drawings Section 2 Drafting Techniques and Skills

Objectives Explain the principles of orthographic projection. Identify the number and types of views needed to make a multiview drawing. Use orthographic projection to create multiview drawings. Explain the differences between third-angle projection and first-angle projection. © Goodheart-Willcox Co., Inc.

Multiview Drawing Used to describe three-dimensional objects in two dimensions. Normally includes three views. Standard arrangement of views used. Created with instruments in manual drafting. Created with drawing commands in CAD. © Goodheart-Willcox Co., Inc.

Standard Arrangement of Views © Goodheart-Willcox Co., Inc.

Orthographic Projection Synonymous with “multiview drawing.” Views obtained by projecting lines of sight (or projectors) to projection plane. Glass box helpful in visualizing views. © Goodheart-Willcox Co., Inc.

Orthographic Projection (Cont.) © Goodheart-Willcox Co., Inc.

Glass Box © Goodheart-Willcox Co., Inc.

Projection Technique Involves three principal planes (or coordinate planes) oriented at right angles. Front view shown in frontal plane. Top view shown on horizontal plane. Side view shown on profile plane. © Goodheart-Willcox Co., Inc.

Principal Planes of Projection Front view also called front elevation. Top view also called plan view. Side view also called end view, side elevation, or end elevation. © Goodheart-Willcox Co., Inc.

Object Views Six views possible for any given object. Height shown in front, side, and rear views. Width shown in top, front, bottom, and rear views. Depth shown in top, side, and bottom views. © Goodheart-Willcox Co., Inc.

Object Views (Cont.) © Goodheart-Willcox Co., Inc.

Projecting Elements Between Views Miter line drawn at 45° to project measurements. Miter line meets projection planes at point between views. Circles and arcs located initially in views where they appear naturally. © Goodheart-Willcox Co., Inc.

Projecting Elements Between Views (Cont.) © Goodheart-Willcox Co., Inc.

Projecting Points To locate point, measure from projection planes. Measure in three directions (width, depth, and height). Points for major features determine other point locations and layout of views. © Goodheart-Willcox Co., Inc.

Drawing Layout © Goodheart-Willcox Co., Inc.

Projecting Lines Process used to represent intersections, edges, and surface limits. Straight line connects two points. Curved line used for arc and curve forms. © Goodheart-Willcox Co., Inc.

Features Represented by Lines © Goodheart-Willcox Co., Inc.

Types of Straight Lines Horizontal lines Vertical lines Inclined lines Oblique lines © Goodheart-Willcox Co., Inc.

Horizontal Lines Parallel to horizontal plane and one other plane. Perpendicular to third plane. Shown true length in two planes. © Goodheart-Willcox Co., Inc.

Vertical Lines Parallel to frontal and profile planes. Perpendicular to horizontal plane. Shown true length in frontal and profile planes. © Goodheart-Willcox Co., Inc.

Inclined Lines Parallel to one projection plane. Inclined and foreshortened in other two planes. © Goodheart-Willcox Co., Inc.

Oblique Lines Neither parallel nor perpendicular to any projection planes. Foreshortened in all three planes. © Goodheart-Willcox Co., Inc.

Projecting Surfaces Plane surfaces and curved surfaces most typical for machine parts. May be done by locating endpoints, plotting series of points, or creating special views. © Goodheart-Willcox Co., Inc.

Types of Surfaces Horizontal surfaces Vertical surfaces Inclined surfaces Oblique surfaces © Goodheart-Willcox Co., Inc.

Single-Curve and Double-Curve Surfaces © Goodheart-Willcox Co., Inc.

Warped Surfaces © Goodheart-Willcox Co., Inc.

Projecting Angles True size projected when plane is parallel to a projection plane. Foreshortening occurs when plane is inclined or oblique. Right angles on inclined planes project true size on two planes. © Goodheart-Willcox Co., Inc.

Projecting Angles (Cont.) © Goodheart-Willcox Co., Inc.

Selecting Views Make front view most descriptive. Identify most representative contour or shape. Identify most natural or functioning position. Arrange views to minimize hidden lines. Consider space requirements. Top and front view typical for long, narrow objects. Front and side view typical for short, broad objects. © Goodheart-Willcox Co., Inc.

Selecting Views (Cont.) Choose between two equally important views unless space or other factors prohibit. Choose right-side view over left-side view. Choose top view over bottom view. © Goodheart-Willcox Co., Inc.

Selecting Views (Cont.) Use only sufficient number of views. One view typically suitable for objects made from thin stock. Two views normally used for cylindrical objects. Three or more views may be required for more complex objects. © Goodheart-Willcox Co., Inc.

Selecting Views (Cont.) © Goodheart-Willcox Co., Inc.

Spacing Views on a Drawing Calculate combined width of front and side views. Add approximately 1 for spacing between views. Divide amount of space remaining between ends of drawing area. Determine vertical spacing in similar manner. © Goodheart-Willcox Co., Inc.

Spacing Views on a Drawing (Cont.) © Goodheart-Willcox Co., Inc.

Conventions for Hidden Lines © Goodheart-Willcox Co., Inc.

Order of Visibility for Coinciding Lines Visible lines Hidden lines Cutting-plane lines Centerlines Break lines Dimension and extension lines Section lines © Goodheart-Willcox Co., Inc.

Removed Views Shown enlarged to clarify detail. Placed at convenient location. Identified in appropriate manner. © Goodheart-Willcox Co., Inc.

Partial Views Typically used for symmetrical parts. Half views Views with break lines Partial side views © Goodheart-Willcox Co., Inc.

Applications for Conventional Drafting Practices Fillets and rounds Runouts Right-hand and left-hand parts Cylinder intersections Radial features Alternate positions Repeated details © Goodheart-Willcox Co., Inc.

Fillet and Round Drawing Practices © Goodheart-Willcox Co., Inc.

Runout Drawing Practices Used for arms, spokes, and webs. Arc should have same radius as fillet or round. © Goodheart-Willcox Co., Inc.

Drawing Right-Hand and Left-Hand Parts Conventional practice used when parts are not interchangeable. View omitted to save time. Note used to indicate information. © Goodheart-Willcox Co., Inc.

Conventional Practices for Intersections © Goodheart-Willcox Co., Inc.

Conventional Practices for Radial Features © Goodheart-Willcox Co., Inc.

Drawing Parts in Alternate Positions Conventional practice used to show limits and clearance. Phantom lines show extents of movement. © Goodheart-Willcox Co., Inc.

Drawing Repeated Details Conventional practice used for common items. Phantom lines indicate missing features. © Goodheart-Willcox Co., Inc.

Orthographic Projection Methods First-angle projection Third-angle projection © Goodheart-Willcox Co., Inc.

Third-Angle Projection Frontal plane located between viewer and object. Views projected forward to frontal plane from third quadrant. Views appear in natural positions. Used in United States and Canada. © Goodheart-Willcox Co., Inc.

Third-Angle Projection (Cont.) © Goodheart-Willcox Co., Inc.

First-Angle Projection Frontal plane located on far side of object from viewer. Views projected to rear from first quadrant. View arrangement different from third-angle projection. Used in European countries. © Goodheart-Willcox Co., Inc.

First-Angle Projection (Cont.) © Goodheart-Willcox Co., Inc.

Drawing Identification Symbols © Goodheart-Willcox Co., Inc.

Visualizing a Three-Dimensional Object from a Multiview Drawing Break views down mentally into geometric shapes. Consider possibilities for each shape. Identify hidden features and object centers. Compare shapes and dimensions in different views. Make freehand sketch. © Goodheart-Willcox Co., Inc.

Visualizing a Three-Dimensional Object from a Multiview Drawing (Cont © Goodheart-Willcox Co., Inc.

Laying Out a Drawing Same principles apply whether drawing manually or using CAD. Manual drawings must have good line quality and accuracy. CAD drawings should be made accurately and efficiently. © Goodheart-Willcox Co., Inc.

Lay Out a Multiview Drawing Select appropriate sheet size and scale. Draw light lines to “block in” views. Locate arcs and circles before lines. Omit hidden lines, centerlines, and dimension lines during layout. Check for missing items. Remove unnecessary construction lines. Darken lines in appropriate order. Letter notes and title block. Check drawing for accuracy and appearance. © Goodheart-Willcox Co., Inc.

Create a Multiview Drawing Define drawing settings and layers or use template. Use Xline command and other commands needed to “block in” views. Draw object lines in each view using drawing commands. Draw hidden lines and centerlines. Draw filleted and chamfered features. Use Text command to create text objects. Freeze layers as needed. Check drawing for accuracy and appearance. © Goodheart-Willcox Co., Inc.

Review Questions 1. In orthographic projection, the projection on the profile plane is called the _____ view. A. top B. front C. plan D. side D. side © Goodheart-Willcox Co., Inc.

Review Questions 2. Which of the following is not a principal projection plane? A. Frontal B. Profile C. Vertical D. Horizontal C. Vertical © Goodheart-Willcox Co., Inc.

Review Questions 3. The _____ box is a helpful drafting aid used to develop skill in visualizing views. glass © Goodheart-Willcox Co., Inc.

Review Questions 4. In the standard arrangement of views, the top view appears above the _____ view. front © Goodheart-Willcox Co., Inc.

Review Questions 5. How many views are typically sufficient for a multiview drawing? A. Three B. Four C. Five D. Six A. Three © Goodheart-Willcox Co., Inc.

Review Questions 6. _____ lines are parallel to one plane of projection and inclined in the other two planes. A. Oblique B. Inclined C. Horizontal D. Vertical B. Inclined © Goodheart-Willcox Co., Inc.

Review Questions 7. _____ surfaces appear true size in the top view. A. Oblique B. Inclined C. Horizontal D. Vertical C. Horizontal © Goodheart-Willcox Co., Inc.

Review Questions 8. The _____ view should be the most representative of the shape of the object. A. top B. front C. side D. end B. front © Goodheart-Willcox Co., Inc.

Review Questions 9. Most drawings made in the United States use _____ projection. A. first-angle B. second-angle C. third-angle D. fourth-angle C. third-angle © Goodheart-Willcox Co., Inc.

Review Questions In _____-angle projection, the frontal projection plane is on the far side of the object from the viewer. first © Goodheart-Willcox Co., Inc.

Glossary Fillet Foreshortened Frontal plane A small, rounded, internal corner. Foreshortened Drawn shorter than true length. Frontal plane The principal projection plane projecting the front view in orthographic projection. © Goodheart-Willcox Co., Inc.

Glossary Hidden lines Horizontal plane Thin lines made up of short evenly spaced dashes, used to indicate edges, surfaces, and corners of an object that are concealed from the view of the observer. Horizontal plane The principal projection plane projecting the top view in orthographic projection. © Goodheart-Willcox Co., Inc.

Glossary Multiview drawing Orthographic projection A projection drawing that incorporates two or more views of a part or assembly on one drawing. Orthographic projection A system of drawing in which a projection of an object is formed on a picture plane by perpendicular projectors from the object to the picture plane. © Goodheart-Willcox Co., Inc.

Glossary Plan view Point The top view of an object. Something having position, but not extension. It has location in space, but no length, depth, or height. © Goodheart-Willcox Co., Inc.

Glossary Principal planes Profile plane The three primary planes (frontal, horizontal, and profile) used to project views in orthographic projection. Profile plane The principal projection plane projecting the side view (or “end” view) in orthographic projection. © Goodheart-Willcox Co., Inc.

Glossary Round Runout A small, rounded, external corner. The intersection of a fillet or round with another surface. © Goodheart-Willcox Co., Inc.