Slide 1Slide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 171Lecture #5 EGR 110 – Engineering GraphicsReading Assignment: Ch. L in Engineering Graphics Workbook, Series 1.2 or Series 2Sketching Assignment: Sketching Assignment #4Chapter L: DimensioningKey topics in dimensioning•Technique in dimensioning – line types, spacing, arrowheads, leaders, radius or diameter, etc.•Placement of dimensions – in which view should a dimension be placed?•Choice of dimensions – which dimensions should be used? Baseline or continued dimensions? Avoiding redundant dimensions.Key types of dimensions•Distances•Angles•Notes2Lecture #5 EGR 110 – Engineering GraphicsLines used in dimensioning•Dimension lines–Thin, dark, solid lines used to show distances and used for leaders–Terminated with arrowheads–Often break in the middle for dimension values–Spacing should be uniform for multiple dimensions•Extension lines–Thin, dark, solid lines extending from object features to the dimension lines–Gaps are generally needed between points on the object and extension lines, except when connecting to center lines3Lecture #5 EGR 110 – Engineering GraphicsCommon rules for placement of dimensions 1) Avoid dimension lines inside objects if possible.2) Shorter dimensions are generally placed closer to the object.3) Dimension lines should generally not cross extension lines.Good Example:Poor Example:Good Example:Poor Example:4Lecture #5 EGR 110 – Engineering GraphicsCommon rules for placement of dimensions 4) Dimension lines should not coincide with or continue a line in a drawing.5) Spacing between dimension lines should be uniform for multiple dimensions.6) Dimensions should be lined up or grouped neatly as much as possible.Good Example:Poor Example:Good Example:Poor Example:7) Dimensions lines are generally perpendicular to extension lines.5Lecture #5 EGR 110 – Engineering GraphicsArrowheads Although styles sometimes vary, arrowheads most commonly use a length:width ratio of 3:1 (this is the default in AutoCAD).13Leaders•Leaders are thin, solid lines used with a note or a dimension•Several styles of leaders and arrows are used in dimensioning circles or arcs•The leader for a circle or arc should always point toward the center•A large dot is often used on the end of a leader for polished surfaces.Examples:6Lecture #5 EGR 110 – Engineering GraphicsSection lines•Section lines are thin, dark lines used to shade or hatch an areaSection Lines•In general, it is best to avoid using inside dimensions, but if you must then the section lines should be interrupted (show example).Good Example:Poor Example:7Lecture #5 EGR 110 – Engineering GraphicsDirection of figuresThere are two primary systems: (show examples)•Unidirectional dimensions (ANSI preferred) - all dimension texts are horizontal from the bottom•Aligned dimensions - all dimension texts are aligned with the dimension linesUnidirectional dimensions Aligned dimensions8Lecture #5 EGR 110 – Engineering GraphicsDimensioning angles•There are several styles for the text, including decimal degrees (default in AutoCAD); degrees, minutes, and seconds; and radians•Dimension lines should form an arc (either inside or outside the angle)Examples:9Lecture #5 EGR 110 – Engineering GraphicsDimensioning Arcs•Use R with the dimension text•Various arrow positions can be used•The dimension may or may not include a center markExamples:10Lecture #5 EGR 110 – Engineering GraphicsDimensioning Holes•Might include center lines, center marks, or none•Several possibilities for leader and arrow positions•Use the symbol  generally (or sometimes DIA)Examples:11Lecture #5 EGR 110 – Engineering GraphicsDimensioning Holes (continued)Dimensions for holes commonly include notes, such as:4, 2 HOLES•2 x 2.5•0.125 DIA DRILL•6 x 2.5 EQUALLY SPACED ON 9.52.5 THRU2.5 BORE2.5 REAMExample:Example:Example: Add a “bolt circle” and the required dimensions12Lecture #5 EGR 110 – Engineering GraphicsFillets and Rounds•Fillet - a rounded inner corner Round - a rounded outer corner•Use a note rather than dimensioning each one. Examples:–6 x R1.25–R0.20 TYP–ALL FILLETS R6 AND ROUNDS R4 –ALL F & R R0.25 UONExamples:13Lecture #5 EGR 110 – Engineering GraphicsSystems of Units1) Decimal inch•Units are generally omitted. A dimension of 1.25 means 1.25".2) Metric (SI System)•Default unit is mm•If units other than mm are used, include a note (such as ALL DIM IN CM)•Include a symbol to indicate that metric units are being used. Examples: • • 3) Fractional inch•Used in architectural drawings, but too inaccurate for machine work•Units are typically used for inches, but not for feet. Examples:•2-3¼"•1-0"•0-5¾"SIMETRIC14Lecture #5 EGR 110 – Engineering GraphicsSymbols1) Counterbore –Symbol:2) Countersink–Symbol:3) Depth–Symbol:Examples:7 THRU CBORE 14 DEPTH 2.57 THRU 14 2.57 THRU CSINK 14 x 907 THRU  14 x 90 Example: Add a dimension for the counterbored hole below.Example: Add a dimension for the countersunk hole below.15Lecture #5 EGR 110 – Engineering GraphicsDimensioning Styles•Continued dimensioning•Baseline dimensioning (datum line) – the use of a baseline helps to reduce the errors that compound with continued dimensionsMiscellaneous notes•Avoid superfluous dimensions•Generally include an overall dimension and omit one continued dimensionExample - Continued dimensions: Example - Baseline dimensions:16Lecture #5 EGR 110 – Engineering GraphicsSize and LocationA good way to check a drawing is to review each feature in the drawing to see if the dimensions clearly show its size and location. Example: The example below includes size and location information for the hole. Add size and location information for the slot.1.24 (size information)1.85 (location information)1.10(location information)17Lecture #5 EGR 110 – Engineering GraphicsPlacement of dimensions - In which view should a dimension be placed?General Rule: Place a dimension in the view where the feature can be most clearly seen.Example - Add decimal inch dimensions to the drawing shown below. When you are done, check each feature to see if