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  • 1.2D ESSENTIALSInstructor: Laura Gerold, PECatalog #10614113Class # 22784, 24113, 24136, & 24138Class Start: January 18, 2012Class End: May 16, 2012

2. Reminders Extra Credit (Write Exam Question) Due TODAY Final Project is due in next week on May 9th. Final Exam is in two weeks on May 16th. 3. QUESTIONS 4. How do you draw faster ellipses? An ellipse template! 5. Can Architectural Standards be Used forDimensions on Project? Architectural Standards can be used 6. How Do you Dimension a Corkscrew? Inside diameter Outside diameter Centerline of the screw diameter Cut a section through the centerline, and put a vertical dimension, or typical dimension on each 7. CHAPTER 10 DIMENSIONING 8. Why Do We Dimension Drawings? Dimensions describe the size, shape, and material ofobjects Give detail on how to build an object from the designer tothe manufacturerSource: 9. UNDERSTANDING DIMENSIONINGThe increasing need for precision manufacturing and interchangeabilityhas shifted responsibility for size control to the design engineer or detail drafter.Practices for dimensioning architecturaland structural drawings are similarin many ways to those for dimensioningmanufactured parts, but some practicesdiffer. Refer to the following standards: ANSI/ASME Y14.5-2009 Dimensioning and Tolerancing ASME Y14.41-2003 Digital Product definition Data Practices Automatically Generated Dimensions. ASME B4.2-1978 (R1999) Preferred Metric Limits and FitsViews and dimensions can be generatedautomatically from a solid model.(Courtesy of Robert Kincaid.) 10. Three Aspects of Good Dimensioning Technique of dimensioningPlacement of dimensions Choice of dimensions 11. Three Aspects of Good Dimensioning Technique of dimensioning Standard appearance of lines Spacing of Dimensions Size of Arrowheads Etc. 12. Three Aspects of Good Dimensioning Placement of dimensions Logical Placement to make dimensions: Legible Easy to Find Easy for the Reader to Interpret 13. Three Aspects of Good Dimensioning Choice of dimensions Show how the design is manufactured Dimension first for Function Add dimensions for ease of manufacturing 14. ToleranceTolerance is the total amount that the feature on the actual part is allowedto vary from what is specified by the drawing or model dimension.ALL TOLERANCES .02 INCHEUNLESS OTHERWISE NOTED.XAMPLESA Title Block Specifying Tolerances. (Courtesy of Dynojet Research, Inc.) 15. LINES USED IN DIMENSIONING Dimension Line A thin, dark, solid line terminated by an arrowhead, indicating the direction and extent of a dimension Usually Perpendicular to extension lines The distance is indicated numerically at the midpoint of the dimension line, either adjacent to the dimension line, or in a gap provided for it. First Dimension Line should be at least 3/8 away from object Subsequent lines can be apart and should be uniform 16. LINES USED IN DIMENSIONING Extension Line Thin, dark, solid line that extends from a point on a drawing towhich a dimension refers Typically Perpendicular to Dimension Lines A small gap (1/16) should be left between the extension lineand the object Extension line should extend 1/8 beyond the outermost arrow An extension line does not have arrows 17. LINES USED IN DIMENSIONING Example Dimension and Extension LinesSource: 18. LINES USED IN DIMENSIONING Centerlines Thin dark line alternating long and short dashes Commonly used as extension lines in locating holes and other symmetrical features When extended for dimensioning, cross over the other lines of a drawing with no gaps End centerlines using a long dash 19. Guidelines for USING DIMENSION AND EXTENSION LINESa. Shorter dimensions are nearest the object outlineb. Do not place shorter dimensions outside, which result in crossing extension linesc. Okay to cross extension lines, but they should not be shortenedd. A dimension line should never coincide with or extend from any line of a drawing 20. Guidelines forUSING DIMENSIONAND EXTENSION LINESDimensions should be lined up and grouped togetheras much as possible. 21. Guidelines forUSING DIMENSIONAND EXTENSION LINESa) Extension and Centerlines must cross visible lines of an object in many cases.b) When this occurs, do not leaves gaps 22. ARROWHEADS Arrowheads Should be uniform in size and style throughout the drawing Length and width should have a ratio of 3:1 Length of arrowhead should be about 1/8 long Should be filled in to look better When you are drawing by hand and using the arrowhead method in which both strokes are directed toward the point, it is easier to make the strokes toward yourself. 23. LEADERSA leader is a thin, solid line directing attention to a note or dimension andstarting with an arrowhead or dot. For the Best Appearance, Make Leaders near each other and parallel across as few lines as possible Dont Make Leaders parallel to nearby lines of the drawing through a corner of the view across each other longer than needed horizontal or vertical 24. Time to Mix up Groups . . . Find a new person to form a group with that sits in adifferent row the you Look for someone that you have not previously teamedwith before Form groups of 2 to 3 people. 25. Group Project Look at the drawings on page 401 & 402 of the text Identify the extension, dimension, center, and leader lines Note the style and location of the arrowheads Dimension a simple block object. Label the lines as extension, dimension, and leader lines. 26. DRAWING SCALE AND DIMENSIONING Drawing scale is noted in the title block. The drawing should not be scaled for dimensions. (Courtesy of Dynojet Research, Inc.)Many standard title blocks include anote such as: DO NOT SCALE DRAWING FOR DIMENSIONS 27. DIRECTION OF DIMENSION VALUES AND NOTESAll dimension values and notes are lettered horizontally to be read from the bottom of thesheet, as oriented by the title block. 28. DIMENSION UNITSA note stating ALL MEASUREMENTS IN MILLIMETERS or ALL MEASUREMENTS ININCHES UNLESS OTHERWISE NOTED is used in the title block to indicate themeasurement units(Courtesy of Dynojet Research, Inc.) 29. MILLIMETER VALUESThe millimeter is thecommonly used unitfor most metricengineeringdrawings. One-placemillimeter decimalsare used whentolerance limitspermit. Two (ormore)placemillimeter decimalsare used whenhigher tolerancesare required. 30. DECIMAL-INCH VALUESTwo-place inch decimals are typical when tolerance limits permit.Three or more decimal places are used for tolerance limits in thethousandths of an inch. In two-place decimals, the second placepreferably should be an even digit. 31. RULES FOR DIMENSION VALUESGood hand-lettering is important for dimension values onsketches. The shop produces according to the directions on thedrawing so to save time and prevent costly mistakes, make alllettering perfectly legible.Make all decimal points bold, allowing ample space. When themetric dimension is a whole number, do not show either a decimalpoint or a zero. When the metric dimension is less than 1 mm, azero precedes the decimal point.When the decimal-inch dimension is used on drawings, a zero is notused before the decimal point of values less than 1 in. 32. DUAL DIMENSIONING andCOMBINATION UNITSDual dimensioning is used to show metric and decimal-inch dimensions on the samedrawing. Two methods of displaying the dual dimensions are:1. Position Method2. Bracket Method DIMENSIONS IN () ARE MILLIMETERS 33. DIMENSION SYMBOLSDimensioning symbols are used to replace traditional terms or abbreviations. (pg 373) Form and Proportion of Dimensioning Symbols.(Reprinted from ASME Y14.5M-1994 (R2004),by permission of The American Society of Mechanical Engineers. All rights reserved.) 34. PLACING AND SHOWING DIMENSIONS LEGIBLYRules for the placement of dimensions help you dimension your drawings sothat they are clear and readableFitting Dimension Values in Limited Spaces (Metric Dimensions) 35. PLACING AND SHOWINGDIMENSIONS LEGIBLY continued 36. Dimensioning by Size (Geometric Breakdown) Engineering structures arecomposed largely of simplegeometric shapes, such asthe prism, cylinder, pyramid,cone, and sphere. Theymay be exterior (positive) orinterior (negative) forms. Positive = exterior (ex. Steelshaft) Negative = interior (ex.Round hole) 37. Dimensioning by Size(Geometric Breakdown) Step 1: Consider thegeometric features of thepart and break them down. In this example, there are: 2 positive prisms 1 positive cylinder 1 negative cone 6 negative cylinders 38. Dimensioning by Size (Geometric Breakdown) Step 2: Specify the size dimensions for each feature bylettering the dimension values as indicated Note that the four cylinders with the same size can bespecified with one dimension 39. Dimensioning by Size (Geometric Breakdown) Step 3: Locate the geometric features with respect toeach other Check to ensure the object is fully dimensioned 40. LOCATION DIMENSIONS After you have specified the sizes of the geometricshapes composing the structure, give locationdimensions to show the relative positions of thesegeometric shapes. (a) rectangular shapes located by faces (b) symmetrical features located by centerlines 41. LOCATION DIMENSIONS Locate holes where the holes appear circular 42. LOCATION DIMENSIONS Use the note 5X to note repetitive features ordimensions X means times 5 means the number of repeated features. Put a space between the X and the dimension Use coordinate dimensions when you needgreater accuracy (c) 43. Group Project: Location vs. Size Dimensions Find an object around the room that has holes or iscomposed of two different geometric items together. Dimension the object first using size and then location The dimensions do not need to be numerical, label themas size or location. Present 44. DIMENSIONING ANGLES Angles are dimensioned by specifying the angle in degrees and alinear dimension. The coordi