2Alphabet of Lines Short Break Line: A freehand drawn line that shows where a part isbroken to reveal detail behind the part orto shorten a long continuous part. (Seeexample of Long Break Lineon the next slide.)Object Line: Thick linesabout .6mm(.032in) that showthe visible edges of an object.Hidden Line: Lines used toshow interior detail that is not visiblefrom the outside of the part.Center Line: Lines that definethe center of arcs, circles, or symmetrical parts.They are half as thick as an object line.Section Lines: Lines are used todefine where there is materialafter a part of the object is cut away.Construction Line: Very lightlydrawn lines used as guides to help drawall other lines and shapes properly.Usually erased after being used.
3Alphabet of Lines Long Break Lines: Break lines are used to either show detail or as in this case they canbe used to shorten very long objects thatdo not change in detail. Notice that this partis 12” long however we have shortenedthe drawing with break lines to useour space more efficiently.Dimension Lines: Lines that are used toshow distance. Arrows are drawn on theends to show where the dimension line starts and ends.The actual distance is usually located in the middle of thisline to let you know the distance being communicated.Dimension lines are used in conjunctionwith extension lines to properlydimension objects.Cutting Plane Line: A line used todesignate where a part has been cutaway to see detail. The arrows shouldpoint in the direction that you arelooking at the cutout.Extension Lines: Lines used to show wherea dimension starts and stops on an object.Used with dimension lines to properly dimensionan object. The line is 1/16” away from thepart as to not get confused with the object linesLeader Lines: Leader lines are used toshow dimensions of arcs, circles and to helpshow detail. An arrow head is used to pointto the part you are dimensioning and the line comesoff the arrow point usually at a 45 degree angle.At the end of this line a horizontal line is drawnwith a note at the end telling informationabout what is being pointed at.How many lines from theprevious slide can you identifyhere?
4Alphabet of lines Phantom Lines: Phantom lines are used to identify alternate positions that a part mytake up. In this example we are using Phantomlines to show that the door handle may only move45 degrees from it’s horizontalposition.How many lines from theprevious 2 slides can youidentify here?
5Orthographic (Multiview Drawings) Pictorial sketches are great for engineers to explain ideas and communicate what the final part will look like to the customer. Unfortunately, pictorial drawings have some disadvantages. Foreshortened views and distorted features do not allow for accurate prototyping. Many times, for parts to be accurately depicted, you need straight on views of each surface.
6Orthographic (Multiview Drawings) In order to obtain these straight line views we have a type of drawing called Orthographic Projection also known as Multiview drawings. Orthographic projection is a way to project a view based on a line of sight that is perpendicular to that view. There are six of these views to any object as shown in the next slide.
7Orthographic (Multiview Drawings) The arrows represent theline of sight associatedwith each view.Use the buttonbelow to jumpbetween thisview and the orthoview on the nextpage.ORTHO
8Orthographic Principal Views Note how the viewsare oriented. Each view isadjacent to the other asif they were unfoldedfrom a 3D shape.Front,Top and Right viewsare used most often. You cansee how other views resemblethese three except they are notas clear due to hidden lines.Click to go backto ISO view.ISO
9Orthographic View Selection Finding the best view of a part can be difficult. Two or more sides may look like the best solution for a front view. On the next slide is a list of characteristics that you should use in choosing your views.
10Orthographic View Selection Steps in selecting the front.Most natural position or use.Shows best shape and characteristic contours.Longest dimensions.Fewest hidden lines.Most stable and natural position.Relationship of other viewsMost contours.Longest side.Least hidden lines.Best natural position.
12Orthographic View Selection Numbers Another decision on view selection you need to make is how many views. You usually do not need more than three but you may only need one or two. The following slides will show when to make a decision between one, and two view drawings.
13One View Selection Two views will be identical Uniform shape. All dimensions easilyshown on one view.
14One View Selection It is also possible to have one view drawings of objects that are flatand have even thickness.Gauges and gaskets aretwo such objects. Wehave a gauge here on theleft.
15Two View Selection Symmetrical parts. A third view would be identical to the otherviewsSecond view is necessary fordepth.
16Precedence of LinesIn multiple view drawings, many times different line types will take up the same space, therefore, we have line precedence. The following is an explanation of which lines exist over others.Object lines over hidden and center.Hidden over center.Cutting plane lines over center lines.The following slide will show an example.
17Precedence of Lines An object line here takes precedence over the center line. However wedraw short thin lines beyond theobject to show there is a center lineunderneath the object line.Object lines took precedence overthe hidden lines you would seefrom the hole. The center line inthe top view would show the depthof the hole as well as the rightside view.
18Do you want to be a good sketcher? PracticeFirst Slide
19Multiview DrawingAnother name for orthographic projection is multiview drawingInvolves visualization and implementationAbility to see clearly in the mind’s eye an objectProcess of drawing the object
20Multiview DrawingA system that allows you to make a two-dimensional drawing of a three-dimensional object
21Viewing ObjectsA box is formed by six mutually perpendicular planes of projection that are located around the object
22Viewing ObjectsLines are formed on the planes by projecting the edges of the object onto the planesThese images are called “views”There are six views formed by the planes of a box
23Viewing ObjectsUnfolding the box produces an arrangement of the six views
24Angles of Projection First-angle projection Used by many European countriesObject is projected onto planes from the first angle or quadrantFront view projected to vertical planeTop view projected to horizontal planeLeft-side view projected to profile plane
25Angles of Projection Third-angle projection Standard for the United StatesThird quadrant is used for projectionFront view projected to vertical planeTop view projected to horizontal planeRight-side view projected to profile plane
26Viewing ObjectsEach view is placed in a constant location relative to the other viewsEach view must be placed in its correct positionViews and features must be aligned
27Choosing Views Most commonly used views Front ViewTop ViewRight Side ViewMost descriptive view is typically designated as the Front View
28Choosing ViewsComplex objects require three views to describe its shapeSimple objects can be described with two viewsEx: Soda CanThin objects can be described with only one viewDepth is given in a noteEx: Erasing Shield
29Choosing the Views Objects described in two views Third view would add nothing to the description of the objectCarefully select views to describe shape of objects accurately
30Curved SurfacesCYLINDERCONESome curved surfaces do not show as curves in all viewsWHEELFRUSTRUM
31Object Dimensions All objects have 3 dimensions HeightDistance from top to bottomWidthDistance from side to sideDepthDistance from the front to back
32Object Dimensions Front View Top View Side View Shows width & height Shows width & depthSide ViewShows height & depth
33Drawing Views of Objects Depth can be projected between views by using a 45° miter line
34Line Types - VisibleEdges that can be seen in a given view areVisible or Object linesVisible lines are thick and dark.028” or .7mmF or HB lead
35Line Types - HiddenEdges that cannot be seen from a given view are indicated by Hidden lines
36Line Types - Hidden Drawing hidden lines .125” (3mm) dashes .0625” (1mm) spaces between dashesThin: .020” (.5mm)Dark: F or HB lead
37Line Types - Hidden Follow rules for hidden line placement Alphabet of LinesDrawings produced with CAD may violate hidden line rules
38Line Types – CenterCenter lines indicate axes of symmetry
39Line Types – Center Perpendicular lines for circular objects Small dashes cross at the center point of featureOne center line drawn to indicate longitudinal axis of cylinder or hole
40Line Types - CenterDraw center lines using a series of long and short dashes.125” (3mm) short the center.75”- 1.5” (20mm-40mm) long dash.0625” (1mm) spaces between dashesThin: .02” (5mm)Long dash extends .125” to .25” beyond feature
41Placement of ViewsViews should be visually balanced within the working space
42Steps for Centering a Drawing Draw border and title block using light construction linesDraw diagonal lines from corners of border
43Steps for Centering a Drawing Add:Width 5.13Space 1.50Depth 2.00Horizontal 8.63Height 3.00SpaceDepthVertical 6.50
44Steps for Centering a Drawing Draw a box the size of all viewsMeasure from the center:Half the widthHalf the height
45Steps for Centering a Drawing Draw in views using light construction lines
46Adding Details Add holes and features Transfer horizontal and vertical featuresUse miter line to transfer depth