Scaling API-first – The story of a global engineering organization
Class 14 presentation
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.
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…
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:
http://www.design-
technology.info/IndPro
d/page11.htm
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 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 Fits 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. 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
E
UNLESS OTHERWISE NOTED.
X
A
M
P
L
E
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:
http://www.theswg
eek.com/2008/05/
29/hide-show-
extension-and-
dimension-lines/
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
a. Shorter dimensions are nearest the object outline
b. Do not place shorter dimensions outside, which result in
crossing extension lines
c. Okay to cross extension lines, but they should not be
shortened
d. 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
a) 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. 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:
1. Position Method
2. Bracket Method DIMENSIONS IN () ARE MILLIMETERS
33. 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)
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
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
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.
