Ellipses by Hand Step 2: Drawing the Curve
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Break up the curve into several points and locate them in the adjacent view
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Plotting Ellipses by Hand step 1
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project the points along projection lines into the top view from the front view. Transfer the depth from the side view, using the back surface as a reference point
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Plotting Ellipses by Hand step 2
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draw the curve through the points
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Plotting Ellipses by Hand step 3
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often machined to form plane or other types of surfaces
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Cylinders
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when curves join each other or plane surfaces smoothly (ex. they are tangent) you do not draw a line to show where they come together
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intersection and tangencies
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if a cylinder is cut by an inclined plane the inclined surface is bounded by an ellipse
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cylinders and ellipses
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if the cut is at 45 degrees from horizontal, it would also appear as a circle in the side view
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cylinders and ellipses
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when the intersection is small, its curved shape is not plotted accurately because it adds little to the sketch or drawing for the time it takes. instead it is shown as a straight line
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intersections of cylinders
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when the intersection is larger, it can be approximated by drawing an arc with the radius the same as that of the larger cylinder
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intersections of cylinders
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a rounded interior corner is called a FILLET
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Fillets and Rounds
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small curves called runouts are used to represent fillets that connect with plane surfaces tangent to cylinders
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Runouts
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a rounded exterior corner is called a ROUND
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Fillets and Rounds
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sharp corners are usually avoided in designing parts to be cast or forged because they are difficult to produce and can weaken the part
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Fillets and Rounds
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the best way to show tangent lines: tangent edges shown as phantom lines in pictorial view
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Tangent Lines
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do not go all the way through
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drilled holes
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go all the way through
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reamed holes
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it is not always possible to show all of the drawing views in alignment on the sheet
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Removed Views
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There are two different ways to indicate the viewing direction for removed views. one is to use a view indicator arrow to show the direction of sight. the other is to use a viewing plane line. clearly label the removed view
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Removed Views
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a plane surface can intersect or be tangent to a contoured surface
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intersection and tangencies
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standard orthographic projections do not always show complex shapes as clearly and simply as you may wish, so certain alternative practices, referred to as conventions, are accepted. while convention is usually a general term for an accepted method, in this case of conventional representations in technical drawings, it refers particularly to simplified representations that enhance economy and clarity in a drawing
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Conventional representations
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conventions are like rules for breaking rules
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Conventional representations
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show sufficient views to completely describe the shape
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necessary views
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show the right-hand view instead of the left-hand view if both show the object equally well
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necessary views
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choose the top view rather than the bottom view
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necessary views
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show long parts horizontally on the sheet for two reasons: 1) they fit better 2) they tend to appear even longer when shown vertically
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necessary views
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make it your goal to communicate the information clearly. if an additional view helps toward this goal, show it. Keep in mind that drawings are easier to read and update if they are simpler, rather than more complex
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necessary views
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a view may not need to be completed, but needs to show what is necessary to clearly describe the object. This is called a partial view and is used to save sketching time and make the drawing less confusing to read.
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Partial Views
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enlarged details are easy to generate using CAD
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Showing enlarged Details
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when adding a detail, draw a circle around the features that will be included in the detail
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Showing Enlarged Details
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To shorten the views of a long object, you an use break lines.
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Conventional Breaks
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Always draw views in the standard arrangement to be sure that your drawings are not misinterpreted.
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Alignment of Views
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A removed view is a complete or partial view removed to another place on the sheet so that it is no longer in direct projection with any other view.
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Removed Views
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Views are labeled, for example, "Plan" for the top view, " East Elevation" for the side view seen from the east compass direction, and so forth.
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Removed Views
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A removed view may be used to show a feature of the object more clearly, possibly to a larger scale, or to save drawing a complete regular view.
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Removed Views
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Architectural drawings often fit even two standard views on the sheet.
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Removed Views
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up and to the right
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front view
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straight on
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top view
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to the left
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Right side view
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A left hand part is not simply a right hand part turned around. The two parts are mirror images and are not interchangeable.
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Right hand and left hand parts
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On sketches and drawings a left hand part is noted as LH and a right hand part as RH.
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Right hand and left hand parts
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Regular multiview projections are sometimes awkward, confusing, or actually misleading.
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Revolution Conventions
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Revolutions like these are frequently used in connection with sectioning. Revolved sectional views are called aligned sections.
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Revolution Conventions
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irregular curves can be plotted by identifying points on the object. The points can be projected to approximate the boundaries of the curved surface
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Chapter 5 Summary
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Drawing conventions define usual practices for the representation of features such as holes, bosses, ribs, webs, lugs, fillets, and rounds
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Chapter 5 Summary
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Use the same main practices to arrange drawing views on the sheet for both hand-drawn and CAD drawings. Show and label enlarged details and removed views. Use partial views and leave out hidden lines as long as the object is shown clearly.
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Chapter 5 Summary
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When curved and planar surfaces intersect, an edge is formed that is represented by a line in the drawing. When curved and planar surfaces are tangent, no edge is formed, so no line is needed. If the drawing is not clear without it, use a phantom line to show tangencies.
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Chapter 5 Summary
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Common types of holes are through, blind, countersunk, counterbored, and spotfaced
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Chapter 5 Summary
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Fillets, rounds, and runout are special types of tangent contours formed on parts with rounded edges
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Chapter 5 Summary
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When necessary for clarity, features are sometimes shown in a revolved position using revolution conventions
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Chapter 5 Summary
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Break lines can be used to leave out a section of a part where it is uniform or repetitive. Often this is done to enlarge the scale of the remaining portions of the part so that details can be seen clearly.
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Chapter 5 Summary
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Sketching is a quick way of visualizing and solving a drawing problem. It is effective way of communicating with all members of the design team.
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Chapter 3 Summary
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There are special techniques for sketching lines, circles, and arcs. These techniques should be practiced so they become second nature
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Chapter 3 Summary
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Using a grid makes sketching in proportion an easy task
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Chapter 3 Summary
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You can sketch circles by constructing a square and locating the four tangent points where the circle touches the square
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Chapter 3 Summary
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A sketched line does not need to look like a CAD or mechanical line. The main distinction between CAD and instrumental drawing and freehand sketching is the character or technique of the line.
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Chapter 3 Summary
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Freehand sketches are made to proportion, but not necessarily to a particular scale
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Chapter 3 Summary
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sketching is one of the most important skills for accurately recording ideas
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Chapter 3 Summary
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isometric, oblique, and perspective are three methods used to create pictorial sketches.
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Chapter 3 Summary
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grid paper can help you maintain proportions by providing a ready-made scale (counting squares)
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What are the advantages of using grid paper for sketching?
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Enclosing Square Method Centerline Method Paper Method
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Methods for sketching a Circle
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thick: visible lines thin: construction line will not reproduce: construction lines
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Sketch the alphabet of line. Which lines are thick? Which are thin? Which are very light and will not reproduce when copied?
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when a great idea hits, or you need to sketch quickly at a meeting or on a job site, you might have access to a CAD system, or even a ruler
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What is the advantage of sketching an object first before drawing it using CAD?
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proportion- accurately represent the size and position of each part in relation to the whole scale- proportionately smaller or larger than the actual size
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What is the difference between proportion and scale?
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Radius Method Trammel Method Tangent Method
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Methods for Sketching Arcs
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Freehand Method Rectangular Method Axes Method Trammel Method
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Methods for Sketching Ellipses
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Orthographic drawings are the result of projecting the image of a 3D object onto one of six standard planes of projection. The six standard views are often thought of as an unfolded glass box. The arrangement of the views in relation to one another is important. Views must project to line up with adjacent views, so that any point in one view projects to line up with that same point in the adjacent view. The standard arrangement of views shows the top, front, and right side of the object.
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Chapter 4 Summary
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Visualization is an important skill for engineers. You can build your visual abilities through practice and through understanding terms describing objects. For example, surfaces can be normal, inclined, or oblique. Normal surfaces appear true size in one principle view and as an edge in the other two principal views. Inclined surfaces appear as an edge view in one of the three principal views. Oblique surfaces do not appear as an edge view in any of the principal views.
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Chapter 4 Summary
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Choice of scale is important for representing objects clearly on the drawing sheet
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Chapter 4 Summary
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Hidden lines are used to show intersections of surfaces, surfaces that appear on edge, and the limits of curved surfaces that are hidden from the viewing direction
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Chapter 4 Summary
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Centerlines are used to show the axis of symmetry for features and paths of motion, and to indicate the arrangement for circular patterns
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Chapter 4 Summary
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Creating CAD drawings involves applying the same concepts as paper drawing. The main difference is that drawing geometry is stored more accurately using a computer than in any hand drawing. CAD drawing geometry can be reused in many ways and plotted to any scale as necessary.
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Chapter 4 Summary
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top, rear, right side, bottom, front, left side
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list the six principal views of projection
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top and right; top; right
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in a drawing that shows the top, front, and right side view, which two views show depth? which views shows depth vertically on the sheet? Which view shows depth horizontally on the drawing sheet?
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normal- parallel to a plane of projection inclined- perpendicular to one plane of projection oblique- tipped to all principal planes of projection
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What is the definition of a normal surface? An inclined surface? An oblique surface?
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width; height; depth
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What dimensions are the same between the top and front view: width, height, or depth? Between the front and right side view? between the top and right side view?
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dividers or a scale
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List two ways of transferring depth between the top and right side views
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flat
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Planar Surfaces
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Cylinder
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Single Curved Surface
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Donut
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Double Curved Surface
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Digital Terrain
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Warped Surface
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3D figures
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solids
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contain solids
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Surfaces
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Sketches and drawings are used to communicate or record ideas about the shape of 3D objects.
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Understanding Solid Objects
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solids that are bounded by plane surfaces
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Polyhedra
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faces of a solid are equal regular polygons
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regular polyhedra
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has two bases, which are parallel equal to polygons, and three or more additional faces, which are parallelograms
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prism
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a right prism has faces and lateral (side) edges that are perpendicular to the bases; an oblique prism has faces and lateral edges that are angles to the bases
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Prisms
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shortened by having a part cut off
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truncated
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has a polygon for a base and a triangular lateral faces that intersect at a common point called the vertex.
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pyramid
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has a single-curved exterior surface
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Cylinders
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has a single curved exterior surface
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Cones
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has a double curved exterior surface
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Spheres
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shaped like a donut; boundary surface is double curved
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torus
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shaped like an egg
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ellipsoids
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the main outlines that separate it from the surrounding space
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contours
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the unoccupied space around it
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negative space
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Artists often begin a sketch by mocking in light guidelines to help them preserve basic shapes and proportions. In technical drawings these are called construction lines
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Construction lines
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Think about breaking down more complex objects into their simpler geometric shapes.
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Essential Shapes
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Bear in mind that you should be thinking in terms of basic shapes whether you are sketching by hand or using CAD. Since basic curves and straight lines are the basis of many of the objects that people create, practice in creating the basic elements of a drawing will help you sketch with ease.
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Analyzing Complex Objects
