1. 2D Essentials Instructor: Laura Gerold, PE Catalog #10614113
Class # 22784, 24113, 24136, & 24138
Class Start: January 18, 2012
Class 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 for Dimensions 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 of objects
Give detail on how to build an object from the designer to the manufacturer
Source:

9. UNDERSTANDING DIMENSIONING
The increasing need for precision manufacturing and interchangeability
has shifted responsibility for size control to the design engineer or detail drafter.
Practices for dimensioning architectural
and structural drawings are similar
in many ways to those for dimensioning
manufactured parts, but some practices
differ.
Refer to the following standards:
• ANSI/ASME Y Dimensioning and Tolerancing
• ASME Y Digital Product definition Data Practices
• ASME B (R1999) Preferred Metric Limits and Fits
Automatically Generated Dimensions. Views and dimensions can be generated automatically from a solid model. (Courtesy of Robert Kincaid.)

10. Three Aspects of Good Dimensioning
Technique of dimensioning
Placement 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. UNLESS OTHERWISE NOTED.
Tolerance
Tolerance is the total amount that the feature on the actual part is allowed
to vary from what is specified by the drawing or model dimension.
ALL TOLERANCES ±.02 INCH
UNLESS OTHERWISE NOTED. E X A M P L S
A 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 ¼” apart and should be uniform

16. LINES USED IN DIMENSIONING
Extension Line
Thin, dark, solid line that extends from a point on a drawing to which a dimension refers
Typically Perpendicular to Dimension Lines
A small gap (1/16”) should be left between the extension line and 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 Lines
Source:

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 LINES
Shorter dimensions are nearest the object outline
Do not place shorter dimensions outside, which result in crossing extension lines
Okay to cross extension lines, but they should not be shortened
A dimension line should never coincide with or extend from any line of a drawing

20. Guidelines for USING DIMENSION AND EXTENSION LINES
Dimensions should be lined up and grouped together as much as possible.

21. Guidelines for USING DIMENSION AND EXTENSION LINES
Extension and Centerlines must cross visible lines of an object in many cases.
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. LEADERS
A leader is a thin, solid line directing attention to a note or dimension and starting with an arrowhead or dot.
For the Best Appearance, Make Leaders
• near each other and parallel
• across as few lines as possible
Don’t 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 a different row the you
Look for someone that you have not previously teamed with 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 a note such as:
DO NOT SCALE DRAWING
FOR DIMENSIONS

27. DIRECTION OF DIMENSION VALUES AND NOTES
All dimension values and notes are lettered horizontally to be read from the bottom of the sheet, as oriented by the title block.

28. DIMENSION UNITS
A note stating ALL MEASUREMENTS IN MILLIMETERS or ALL MEASUREMENTS IN INCHES UNLESS OTHERWISE NOTED is used in the title block to indicate the measurement units…
(Courtesy of Dynojet Research, Inc.)

29. 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.

30. DECIMAL-INCH VALUES
Two-place inch decimals are typical when tolerance limits permit. Three or more decimal places are used for tolerance limits in the thousandths of an inch. In two-place decimals, the second place preferably should be an even digit.

31. RULES FOR DIMENSION VALUES
Good hand-lettering is important for dimension values on sketches. The shop produces according to the directions on the drawing so to save time and prevent costly mistakes, make all lettering perfectly legible.
Make all decimal points bold, allowing ample space. When the metric dimension is a whole number, do not show either a decimal point or a zero. When the metric dimension is less than 1 mm, a zero precedes the decimal point.
When the decimal-inch dimension is used on drawings, a zero is not used before the decimal point of values less than 1 in.

32. DUAL DIMENSIONING and COMBINATION UNITS
Dual dimensioning is used to show metric and decimal-inch dimensions on the same drawing. Two methods of displaying the dual dimensions are:
Position Method
Bracket Method
DIMENSIONS IN () ARE MILLIMETERS

33. Form and Proportion of Dimensioning Symbols.
DIMENSION SYMBOLS
Dimensioning 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 LEGIBLY
Rules for the placement of dimensions help you dimension your drawings so that they are clear and readable…
Fitting Dimension Values in Limited Spaces (Metric Dimensions)

35. PLACING AND SHOWING DIMENSIONS LEGIBLY continued…

36. Dimensioning by Size (Geometric Breakdown)
Engineering structures are composed largely of simple geometric shapes, such as the prism, cylinder, pyramid, cone, and sphere. They may be exterior (positive) or interior (negative) forms.
Positive = exterior (ex. Steel shaft)
Negative = interior (ex. Round hole)

37. Dimensioning by Size (Geometric Breakdown)
Step 1: Consider the geometric features of the part 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 by lettering the dimension values as indicated
Note that the four cylinders with the same size can be specified with one dimension

39. Dimensioning by Size (Geometric Breakdown)
Step 3: Locate the geometric features with respect to each other
Check to ensure the object is fully dimensioned

40. LOCATION DIMENSIONS
After you have specified the sizes of the geometric shapes composing the structure, give location dimensions to show the relative positions of these geometric 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 or dimensions
X means times
5 means the number of repeated features.
Put a space between the X and the dimension
Use coordinate dimensions when you need greater accuracy (c)

43. Group Project: Location vs. Size Dimensions
Find an object around the room that has holes or is composed of two different geometric items together.
Dimension the object first using size and then location
The dimensions do not need to be numerical, label them as “size” or “location.”
Present

44. DIMENSIONING ANGLES
Angles are dimensioned by specifying the angle in degrees and a linear dimension.
The coordinate method is better when a high degree of accuracy is required
In civil engineering projects, ratios are used with one member of the ratio equal to 1.

45. DIMENSIONING ANGLES – GROUP PROJECT
Using a simple object with an inclined surface, dimension the angle
Use both degrees and a linear dimension
Present

46. DIMENSIONING ARCS
A circular arc is dimensioned in the view where its true shape in seen by giving the value for its radius preceded by the abbreviation R.
The center is marked with small crosses to clarify the drawing (except when small, unimportant, or undimensioned arcs)
When there is enough room, both the radius value and arrowhead are placed inside the arc
If not, the arrowhead is left inside, but the value is moved outside or both are moved out
False center may be indicated with dimension line jogged to it (f)

47. DIMENSIONING FILLETS AND ROUNDS
Dimensioned like other arcs
If there are few and they are obviously the same size, only dimension one
If numerous and a standard size, use notes such as the following:
FILLETS R6 AND ROUNDS R3 UNLESS OTHERWISE SPECIFIED or
ALL CASTING RADII R6 UNLESS NOTED
or simply
ALL FILLETS AND ROUNDS R6.

48. Group Project – Dimensioning Arcs
Use a simple object with an arc that I have, that is around the room, or that you brought with you
Dimension the arc using a couple of different methods discussed
Present

49. FINISH MARKS
A finish mark is used to indicate that a surface is to be machined, or finished, as on a rough casting or forging. To the patternmaker or diemaker, a finish mark means that allowance of extra metal in the rough workpiece must be provided for the machining.

50. FINISH MARKS
There are three styles of finish marks as shown on the figure below
(c) shows a simple casting having several finished surfaces
(d) shows on finish marks are indicated on the drawing.
The finish mark is shown on the edge view of the finished surface and is repeated in any other view in which the surface appears as a line, even a hidden line

51. FINISH MARKS
A finish mark point should be directed inward toward the body of the metal similar to a tool bit (a)
It should be shown upside down (b)

52. FINISH MARKS GROUP PROJECT
Build a simple block item
Draw the necessary views
Apply finish marks
Compare your finish marks with another group
Present

53. SIZE DIMENSIONING HOLES
The leader of a note should point to the circular view of the hole, if possible.
Arrowhead should touch the outer circle
How would you read the dimensions on the object below?

54. SIZE DIMENSIONING HOLES
When the circular view of a hole has two or more concentric circles (counterbored, countersunk, spotfaced, or tapped holes), the arrowhead should touch the outer circle.
Draw a radial leader line, a line that would pass through the center of the circle if extended

55. SIZE DIMENSIONING HOLES
Countersunk, counterbored, spotfaced and tapped holes are usually specified by standard symbols or abbreviations.
As a group, figure out the symbols on the above figures (see page 379 & 380 in text)
Present

56. GROUP PROJECT - SIZE DIMENSIONING HOLES
Draw one block with the center hole, or another object with a hole
Dimension the hole
Present

57. DIMENSIONING CURVES
One way to dimension curves is to give a group of radii (a)
On (a), a jog is made in the dimension line if the radius is inaccessible
On (b), the outline envelope of the curved surface is dimensioned and the radii are self-locating from “floating centers”
Both circular and noncircular curves may be dimensioned by using coordinate dimensions, or datums (c). .

58. DIMENSIONING CURVES
When angular measurements are unsatisfactory, you may give chordal dimensions (a)
Or you can give linear dimensions on curved surfaces (b)

59. DIMENSIONING CURVES – GROUP PROJECT
Sketch a simple curved surface
Practice using the different methods of dimensioning the curved surface as discussed on the previous two slides (and as shown on page 382 & 383 of the text)
Which method do you prefer?
Present

60. DIMENSIONING PRISMS
Height and width are usually given in the front view
Depth is given in the top view
Vertical dimensions are placed on the left or right, usually inline
Place the horizontal dimensions between views

61. DIMENSIONING PRISMS – GROUP PROJECT
Draw the necessary views of a simple rectangular prism
Dimension the prism
Present

62. SIZE DIMENSIONS: CYLINDERS
Cylinders are usually dimensioned by giving the diameter and length where the cylinder appears as a rectangle.
The radius of a cylinder should never be given.
Use “Ø” to indicate circular shape

63. SIZE DIMENSIONS: CYLINDERS
Dimensioning a Machine Part Composed of Cylindrical Shapes

64. SIZE DIMENSIONS: CYLINDERS – GROUP PROJECT
Sketch the necessary views of a simple cylinder
Dimension the cylinder
Present

65. CONTOUR DIMENSIONING PRINCIPLE
Dimension features should be attached to the view where the feature’s shape is best shown

66. SUPERFLUOUS DIMENSIONS
All necessary dimensions must be shown, but do not give unnecessary or superfluous dimensions.

67. SUPERFLUOUS DIMENSIONS continued…
No unnecessary or superfluous dimensions.

68. Project Time! Share your projects with your group.
Discuss dimensioning your project.
Do you have any final questions to finish your project?

69. What’s Next? Finish Lingering Questions from Chapter 8 and Chapter 10
Review for Final Exam

70. Questions?
On one of your sketches, answer the following two questions:
What was the most useful thing that you learned today?
What do you still have questions about?
What specific items would you like to review next week before the exam?

71. LAST Homework
Chapter 10 Review Questions: 2, 4, 5, 7, 8, 10, 13 Chapter 10 Exercises: 10.1 (a) – use any scale, just define it.