Dimensioning Chapter 9

2 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Objectives Use conventional dimensioning techniques to describe size and shape accurately on an engineering drawing Create and read a drawing at a specified scale Correctly place dimension lines, extension lines, angles, and notes

3 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Objectives (cont.) Use aligned and unidirectional dimensioning systems Dimension circles, arcs, and inclined surfaces Identify precision ranges for typical manufacturing operations Apply finish symbols and notes to a drawing

4 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Objectives (cont.) Dimension contours Use standard practices for dimensioning prisms, cylinders, holes, curves List practices for dimensioning a solid model as documentation Identify guidelines for the do’s and don’ts of dimensioning

5 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Understanding Dimensioning Drawings for products must be dimensioned so that production personnel all over the world can make mating parts that will fit properly when assembled or when used to replace parts

6 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Aspects of Good Dimensioning Dimensions are given in the form of distances, angles, and notes regardless of the dimensioning units being used The ability to create good dimensions requires: Technique of dimensioning Placement of dimensions Choice of dimensions

7 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Tolerance When a finished part is measured it may vary slightly from the exact dimension specified Tolerance is the total amount that the feature on the actual part is allowed to vary from what is specified by the dimension

8 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Lines Used in Dimensioning Dimension line – a thin, dark, solid line terminated by arrowheads, indicating the direction and extent of a dimension

9 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Lines Used in Dimensioning Extension line – a thin, dark, solid line that extends from a point on the drawing to which a dimension refers

10 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Lines Used in Dimensioning Centerline – a thin, dark line alternating long and short dashes commonly used in locating holes and other symmetrical features

11 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Using Dimension and Extension Lines Shorter dimension lines are nearest the object outline Dimension lines should not cross extension lines A dimension line should never coincide with or extend any line of the drawing Avoid crossing dimension lines when possible

12 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Using Dimension and Extension Lines

13 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Using Dimension and Extension Lines Dimensions should be lined up and grouped together as much as possible

14 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Using Dimension and Extension Lines When extension lines or center lines cross visible object lines, gaps should not be left in the lines

15 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Arrowheads Arrowheads indicate the extent of dimensions They should be uniform in size and style throughout the drawing

16 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Leaders A leader is a thin solid line directing attention to a note or dimension and starting with an arrowhead or dot

17 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Drawing Scale and Dimensioning Drawings are usually made to a scale which is indicated in the title block A heavy straight line should be drawn under any single dimension value that is not to scale If an entire drawing is not prepared to a standard, note NONE in the scale area of the title block

18 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Direction of Dimension Values and Notes All dimension values and notes are lettered horizontally and should read from the bottom of the sheet The exception is when dimensioning from a baseline as in coordinate dimensioning

19 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Direction of Dimension Values and Notes

20 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Dimension Units Dimension values are shown using the metric system or decimal inch values It is standard practice to omit millimeter designations and inch marks on drawings and note the units in the title block except when there is a possibility of misunderstanding

21 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Dimension Units Either meters or feet and inches and fractional inches are used in architectural and structural work In U.S. structural and architectural drafting, all dimensions of 1 foot or over are usually expressed in feet and inches

22 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Millimeter Values The millimeter is the commonly used unit for most metric engineering drawings One-place millimeter decimals are used when tolerance limits permit Two or more-place millimeter decimals are used when higher tolerances are required

23 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Decimal Inch Values Two-place decimals are typical when tolerance limits permit In two-place decimals, the second place preferably should be an even digit so that when the dimension is divided by 2 the results will still be a two-place decimal

24 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Rules for Dimension Values Where the metric dimension is a whole number, do not show a decimal point or a zero Where the metric dimension is less than 1mm, a zero precedes the decimal point Where the decimal-inch dimension is used, a zero is not used before the decimal point of values less than 1

25 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Rounding Values If the number following the rounding position is a 5, round to an even number If the number following the rounding position is less then 5, make no change If the number following the rounding position is more than 5, round up

26 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Dual Dimensioning Dual dimensioning is used to show metric and decimal inch dimensions on the same drawing

27 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Dimension Symbols

28 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Placing Dimensions Never letter a dimension value over any line on the drawing In a group of parallel dimension lines, the dimension values should be staggered Do not crowd dimension figures into limited spaces making them illegible

29 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Placing Dimensions Place dimensions between views when possible, but only attached to a single view Dimensions should not be placed on a view unless doing so promotes the clarity of the drawing

30 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Placing Dimensions When a dimension must be placed in a hatched area or on the view, leave an opening in the hatching or a break in the lines for the dimension value

31 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Placing Dimensions Avoid dimensioning to hidden lines Do not attach dimensions to visible lines where the meaning is not clear Notes for holes are usually placed where you see the circular shape of the hole An external cylindrical shape is dimensioned where it appears rectangular

32 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Placing Dimensions Give dimensions where the contours of the object are defined

33 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Superfluous Dimensions All necessary dimensions must be shown but avoid giving unnecessary dimensions Do not repeat dimensions on the same view or on different views, or give the same information two different ways

34 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Superfluous Dimensions

35 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Dimensioning Angles You should dimension angles by specifying the angle in degrees and a linear dimension

36 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Dimensioning Arcs A circular arc is dimensioned in the view where you see its true shape by giving the value for its radius preceded by the abbreviation R

37 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Fillets and Rounds Individual fillets and rounds are dimensioned like other arcs If there are only a few and they are obviously the same size, giving one typical radius is preferred Fillets radii can also be given in a general note

38 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Size Dimensions: Prisms

39 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Size Dimensions: Cylinders

40 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Size Dimensions: Holes

41 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Dimensioning Various Shapes

42 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Dimensioning Curves

43 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Dimensioning Curved Surfaces

44 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Dimensioning Rounded-end Shapes

45 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Dimensioning Threads

46 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Dimensioning Tapers

47 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Dimensioning Chamfers

48 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Shaft Centers

49 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Dimensioning Keyways

50 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Dimensioning Knurls

51 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Finish Marks A finish mark is used to indicate that a surface is to be machined

52 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Surface Roughness

53 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Location Dimensions

54 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Location Dimensions

55 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Location Dimensions

56 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Location Dimensions

57 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Mating Dimensions

58 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Tabular Dimensions

59 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Coordinate Dimensioning Basic coordinate dimensioning practices are generally compatible with the data requirements for automated production A set of three mutually perpendicular datum or reference planes is usually required for coordinate dimensioning

60 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Coordinate Dimensioning

61 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Coordinate Dimensioning

62 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Machine, Pattern, and Forging Dimensions

63 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Sheet-Metal Bends In sheet-metal dimensioning, allowance must be made for bends

64 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Notes It is usually necessary to supplement the direct dimensions with notes Notes should be worded to allow only one interpretation Notes should be lettered horizontally

65 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Standards Dimensions should be given to make use of readily available materials, tools, parts, and gages The dimensions for many commonly used machine elements are standardized and can be obtained from standard manuals or catalogs