9Class WorkDraw each problem on a separate sheet and complete as indicated.
10Dimensioning and Notes What is Dimensions?Define the size of the geometrical features of an object.What are notes?Provide additional information not found in the dimensions.Usually presented in inches or millimeters using decimals to make it easier.
11Reading Directions of Dimensions UnidirectionalPlaced to read from the bottom of the drawing.AlignedPlaced parallel to the dimension line
12Rules for Dimensioning Place dimensions on the views that show the true shape of the object.Unless absolutely necessary, dimensions should not be placed within the views.If possible dimensions should be grouped together rather than scattered about the drawing.Dimensions must be complete, no scaling of the drawing is required. Possible to determine size and shapes w/o assuming any measurements.
13Rules for Dimensioning (Cont.) Draw dimension lines parallel to the direction of measurements. If there are several parallel dimension lines, stagger the values.Dimensions should not be duplicated unless they are absolutely necessary to the understanding of the drawings.Plan your work carefully so the dimension lines do not cross extension lines.When all dimensions on a drawing are in inches, the inch symbol (“) should not be used. Dimensions on metric drawings are in millimeters unless otherwise noted.
15Circles, Holes and Arcs ANSI (American National Standards Institute) “fi” Φ, Greek symbol, indicates the dimension is a diameter. And is placed before the dimension.Symbols of depth of a hole.
16LeadersEmployed to direct attention to a note or to indicate size of arcs and circles.When used on a circle or arc, the leader should always point to the center of the diameter.
17ArcsDimensioned by giving the radius and placing a capital R in front of the dimension.
18More on Circular Dimensioning Equally Spaced HolesAlways from the centers.
19More on Dimensioning Dimensioning Angles Expressed normally in Degrees (°)Dimensioning small portions of an ObjectExtension lines indicate object being dimensioned but value written off to the side
20Sectional and Auxiliary Views Sectional ViewsHow an object would look if a cut were made through it perpendicular an exact right angle) to the direction of sight.Necessary for a clear understanding of the shape of complicated parts.
21Types of Sectional Views Full sectionMade thru the entire object.Half SectionShape of ½ of the interior & ½ the exterior features. Normally suited for Symmetrical Objects- objects having same size, shape and relative position on opposite sides of a dividing line or plane.Revolved SectionPrimarily utilized to show shape of objects as spokes, ribs and stock metal objects.
22Types of Sectional Views (cont.) Aligned SectionRemoved SectionUsed when it isn't possible to draw a needed sectional view on one of the regular views.Offset SectionUses cutting plane that is stepped or offset to pass through the required features.Broken-out SectionEmployed when a small portion of a sectional view will provide required information
25Auxiliary ViewNeeded to show the true length and true width of the angular surface.Can be projected from any view that shows the angled surface as a line.Front Auxiliary taken from the Front ViewTop Auxiliary taken from the Top ViewRight Auxiliary taken from the Right View.