1. Dimensioning Standards
Introduction to Engineering Design
© 2012 Project Lead The Way, Inc.

2. Dimensioning Standards
In order for the drawings to be dimensioned so that all people can understand them, we need to follow standards that every company in the world must follow. Standards are created by these organizations:
ANSI
ISO
MIL
DOD
CEN
DIN
JIS

3. Standards Institutions
ANSI - American National Standards Institute. This institute creates the engineering standards for North America.
ISO - International Organization for Standardization. This is a worldwide organization that creates engineering standards with approximately 100 participating countries.

4. Standards Institutions
The United States military has two organizations that develop standards.
DOD - Department Of Defense
MIL - Military Standard

5. Standards Institutions
DIN - Deutsches Institut für Normung. The German Standards Institute created many standards used worldwide, including the standards for camera film.
JIS - Japanese Industrial Standard. Created after WWII for Japanese standards.
CEN - European Standards Organization.

6. Dimension Components Dimension Line Dimension Text Arrow Head
Extension Lines

7. Dimension Text Guidelines
If the dimension text will not fit between the extension lines, it may be placed outside them

8. Dimension Text Guidelines
Dimension text is placed in the middle of the line both horizontally
and vertically

9. Dimensioning Methods
Dimensions are represented on a drawing using one of two systems, unidirectional or aligned.
The unidirectional method means all dimensions are read in the same direction.
The aligned method means the dimensions are read in alignment with the dimension lines or side of the part, some read horizontally and others read vertically.

10. Dimensioning Methods Aligned Unidirectional
Dimensions are placed so that they can be read from the bottom of the drawing sheet. This method is commonly used in mechanical drafting.
Aligned
Dimensions are placed so the horizontal dimensions can be read from the bottom of the drawing sheet and the vertical dimensions can be read from the right side of the drawing sheet. This method is commonly used in architectural and structural drafting.

11. Classification of Dimensions
Size. Dimensions are used to identify the specific size of a feature on an object.
Location. Dimensions are used to identify the physical proximity of a feature to another feature within an object.
Size dimension
Location dimension
Location dimension
Size dimension

12. Linear Dimensioning Chain Dimensioning
Dimensioning from feature to feature
Common dimensioning technique

13. Chain Dimensioning Examples
Presentation Name
Course Name
Unit # – Lesson #.# – Lesson Name
Chain Dimensioning Examples
METHOD 1
METHOD 2
Dimension from feature to feature across entire part
Manufacturing inaccuracies can accumulate
Dimension from feature to feature except omit one partial dimension in the chain
Dimension overall length/width/height to limit manufacturing inaccuracies
Preferable chain dimensioning method
It is impossible to manufacture a part to an exact dimension. If a part is measured precisely enough, the part configuration will deviate from the specified dimensions. Typically a small amount of deviation from the specified dimension is allowed, but the error can add up in a chain of dimensions compounding the error and resulting in a part that is much smaller or larger than intended. Therefore, specifying the overall dimension (with its small allowable error in that one dimension) will reduce the deviation of the overall part size. We will talk about tolerances, the allowed deviation of a dimension on a manufactured part from the specified dimension, later in this unit.
For now, when chain dimensioning, use the preferred method (Method 2) when possible.

14. Datum Dimensioning Datum Dimensioning
Dimensioning from a single point of origin called a DATUM
Reduces dimensional deviations in manufactured parts because each size/location dimension is referenced to a single point

15. Datum Dimensioning

16. Dimensioning Symbols Presentation Name Course Name
Unit # – Lesson #.# – Lesson Name
Dimensioning Symbols
Some common dimensioning symbols.

17. Dimensioning Angles
Angled surface may be dimensioned using coordinate method to specify the two location distances of the angle.
Angled surfaces may also be dimensioned using the angular method by specifying one location for distance and the angle.
Coordinate Method
Angular Method

18. Dimensioning Chamfers
Presentation Name
Course Name
Unit # – Lesson #.# – Lesson Name
Dimensioning Chamfers
Internal Chamfers
Two options for 45 degree external chamfers
Chamfers are used on outside edges to avoid sharp corners for safety and handling.
External chamfers other than 45 degrees

19. Dimensioning Arcs and Circles
Arcs and circles are dimensioned in views that show the arc or circle.
Arcs are dimensioned with a leader to identify the radius; in some cases, a center mark is included.
Circles should have a center mark and are dimensioned with a leader to identify the diameter.

20. Dimensioning Arcs Use a capital R to indicate radius
Arrows can be inside or outside for small arcs.
Small arcs do not need center marks.
Large arcs need a center mark

21. Presentation Name
Course Name
Unit # – Lesson #.# – Lesson Name
Fillets and Rounds
Fillet. An inside radius between two intersecting planes
Round. An outside radius applied to corners
Fillet
Round
A round is used to avoid sharp edges for safety and handling. A fillet is used to provide strength at inside corners to avoid fracture. In addition fillets and rounds (as opposed to sharp corners) can make it easier to remove molded parts from molds.
Identify which arcs are fillets and which are rounds.

22. Dimensioning Circles Holes should use hole notes
Full circles should be dimensioned using the diameter
This hole note specifies a hole with a diameter and 1.00 deep

23. Cylindrical parts may be dimensioned in this manner
Dimensioning Circles
Cylindrical parts may be dimensioned in this manner
Note that the diameter symbol is used so that the dimension is not assumed to be linear

24. Dimensioning Splines and Curves
Points are placed along the contour of splines and dimensioned from a datum.
DATUM

25. Dimensioning Splines and Curves
Presentation Name
Course Name
Unit # – Lesson #.# – Lesson Name
Dimensioning Splines and Curves
This section view provides coordinate dimensions for the curvature of the windshield of the Automoblox T9 truck. We refer to these dimensions as coordinate dimensions because the horizontal and vertical distances from a given point, the datum (or origin), are given for each identified point along the curve.
DATUM

26. Reference Dimensions
“X” indicates the number of places (or occurrences)
2 X indicates that there are two identical holes

27. Dimensioning Radial Patterns
Angles and radius values are used to locate the center of radially patterned features

28. Alternate Views Introduction to Engineering Design
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29. Presentation Name
Course Name
Unit # – Lesson #.# – Lesson Name
Alternate Views
In some cases, orthogonal projections and pictorials are not sufficient to specify all the details of a part.
Section View. Used to show “inside” details not apparent on the exterior of the part
Auxiliary View. Used to show features that are located on an inclined surface in true size and shape
Detail View. Used to show a “close-up” view of features that are too small to adequately specify in another view

30. Section View Provides a view of an object as if it were cut by a saw
Location is indicated by a cutting plane line on another view
Cutting plane line

31. Section View Cutting plane line Indicates location of the cut
Thick and broken line
Arrows indicate direction of view
Labeled with a letter for identification on drawing
Cutting plane line

32. Section View Section lines
Hatch lines that indicate material that was “cut” at the cutting plane line
Thin lines
Section lines
Cutting plane line

33. Section View
Types
Full Section
Half Section
Offset Section

34. Full Section Cutting plane line passes fully through the part
The part of the object behind the cutting plane line (away from the direction of the arrows) is removed

35. Full Section Example
Section lines indicate material that is cut by the cutting plane line
Imagine the part is cut at cutting plane line
Direction of View
This half of the part is removed

36. Full Section Example
Section lines indicate material that is cut by the cutting plane line
Imagine the part is cut at cutting plane line
Direction of View
This half of the part is removed

37. Half Section
Used on symmetrical parts to show inside as well as outside details in one view
One quarter of the part is cut away
Cutting plane line goes halfway through the part

38. Half Section Example Half Section
Only one arrowhead in the direction of view
Note that the cutting plane line cuts away a quarter of the part
Half Section

39. Offset Section
Interior features not in line with each other can be shown in an offset section view
Note how the cutting plane line changes direction and follows the center of each feature

40. Presentation Name
Course Name
Unit # – Lesson #.# – Lesson Name
Auxiliary Views
Orthographic projection of an inclined plane (angled surface) which appears foreshortened in a principle orthographic projection
Used to show the true size and shape of an inclined plane and the features on it

41. Auxiliary Views
Foreshortened surfaces do not give a clear or accurate representation of the size or shape of the surface or features and should not be dimensioned
foreshortened face
TOP
FRONT
RIGHT SIDE

42. Presentation Name
Course Name
Unit # – Lesson #.# – Lesson Name
Auxiliary Views
An auxiliary view allows the viewer to look perpendicular to an angled surface to witness the true size and shape of that surface and its features (a hole in this example).
True Height
Auxiliary Distance
TOP
We will not use auxiliary views in this unit, but they will be presented in more detail in Unit 8.
FRONT
RIGHT SIDE

43. Detail Views
An enlargement of a portion of another view to illustrate small features on a part
Not to be confused with a Detail Drawing which is any drawing that contains all the information needed to manufacture a part

44. Detail View Example
A feature is broken out and enlarged for clarity

45. Holes and Hole Notes Introduction to Engineering Design
© 2012 Project Lead The Way, Inc.

46. Hole Definitions Through/Thru Clearance Blind
Hole cuts through entire thickness
Clearance
Hole large enough to allow screw head (and driver) to pass through
Blind
Hole does not cut through entire thickness

47. Hole Definitions Countersink Counterbore Tapped
Conical-shaped recess around hole at surface
Often used to accept tapered screw
Counterbore
Cylindrical recess around hole at surface
Often used to receive a bolt head or nut
Tapped
Hole has internal threads

48. Hole Note Symbols

49. Hole Notes
A 0.25” diameter blind hole is drilled 0.75” deep. Then a 0.38” diameter counter bore is drilled 0.25” deep.
Counterbore or Spotface symbol
Depth
symbol

50. Hole Notes
A 0.38” diameter blind hole is drilled 0.50” deep.

51. Hole Notes
A 0.38” diameter hole is drilled completely through the object.

52. Hole Notes
Countersink or symbol
A 0.50” diameter hole is drilled completely through the object. Then a countersink is created with a 1.00” diameter at the surface and tapering at 82º.

53. Thread Notes Thread are dimensioned with the use of local notes.
Two methods
Unified National Thread method
ISO

54. Unified National Thread Notes
Thread per Inch
Major Diameter
Coarse or Fine threads. In this case C for course, F is for fine.

55. ISO Thread Notes 1.5, Pitch of the threads 12, Nominal Diameter in mm
Prior to THRU may appear an LH for Left Hand thread
M for Metric
H, allowance. H means no allowance, G means tight allowance.
6, Grade of tolerance in the threads. Can be whole number from 3 to 9.

56. Tolerances Introduction to Engineering Design
© 2012 Project Lead The Way, Inc.

57. Tolerances Variation is unavoidable
Presentation Name
Course Name
Unit # – Lesson #.# – Lesson Name
Tolerances
Variation is unavoidable
No two manufactured parts are identical – some degree of variation will exist
Tolerances are used in production drawings to control the manufacturing process and control the variation between copies of the same part
In particular, tolerances are applied to mating parts in an assembly
One advantage in using tolerances is that interchangeable parts can be used
Without tolerances, copies of individual parts could vary significantly, disallowing the use of a copy of the part because is does not fit or does not operate properly within an assembly.

58. Do not specify a tolerance that is smaller than necessary!
Presentation Name
Course Name
Unit # – Lesson #.# – Lesson Name
Tolerances
Large tolerance may affect functionality of part
Specify tolerances to ensure proper function
Small tolerance will affect the cost of the part
Cost generally increases with smaller tolerances
Will require precise manufacturing
Will require quality control with inspection and rejection of parts
Do not specify a tolerance that is smaller than necessary!
Without tolerances, copies of individual parts could vary significantly, disallowing the use of a copy of the part because is does not fit or does not operate properly within an assembly.

59. Tolerances ANSI/ASME Standard Y14.5
Each dimension shall have a tolerance, except those dimensions specifically identified as reference, maximum, minimum, or stock. The tolerance may be applied directly to the dimension or indicated by a general note located in the title block of the drawing.

60. Tolerances
A tolerance is an acceptable amount of dimensional variation that will still allow an object to function correctly.

61. Tolerances
Three basic tolerances that occur most often on working drawings are:
limit dimensions
bilateral tolerance
unilateral tolerance

62. Presentation Name
Course Name
Unit # – Lesson #.# – Lesson Name
Limit Dimensions
Provide an upper limit and lower limit for the dimension.
Any size between or equal to the upper limit and/or lower limit is allowed
The upper limit dimension is 0.126
The lower limit dimension is 0.125

63. Bilateral Tolerance
Provides an equal allowable variation, larger and smaller
Uses a plus/minus (±) symbol to specify the allowable variation
Counter bore depth can be .003 larger or smaller than .25
Hole location can be .05 larger or smaller than 1.50

64. Unilateral Tolerance
Provides an allowable variation in only one direction (either larger or smaller)
Uses separate plus (+) and minus (–) signs
The hole diameter may vary .004 larger but may not be smaller than .500

65. Tolerances Identify the type of tolerance displayed in red
Presentation Name
Course Name
Unit # – Lesson #.# – Lesson Name
Tolerances
Identify the type of tolerance displayed in red
Limit dimensions
Bilateral
Unilateral
Have students identify each type of tolerance displayed in red. Start with the upper left. Have students offer their answers, then click to reveal the correct tolerance type. Proceed to middle red dimension, then lower right dimension.

66. Definitions
Specified Dimension is the target dimension from which the limits are calculated
Specified dimension
1.50

67. Definitions
Limits are the maximum and minimum sizes shown by the toleranced dimension
Upper limit is the maximum allowable dimension
Lower limit is the minimum allowable dimension
Upper Limit = Specified Dimension + positive variance
1.55 =
Lower Limit = Specified Dimension + negative variance
1.45 = (– 0.05)

68. Presentation Name
Course Name
Unit # – Lesson #.# – Lesson Name
Definitions
Tolerance is the total variance in a dimension and is equal to the difference between the upper and lower limits.
Tolerance = Upper Limit – Lower Limit
0.10 = 1.55 – 1.45
If a part is manufactured outside of the limits established by the tolerance, the part is said to be “out of tolerance”.

69. Calculating Tolerance
.010
- .05
+ .05
1.45
1.50
1.55
Lower Limit
Upper Limit
Tolerance = Upper Limit – Lower Limit
0.10 = 1.55 – 1.45

70. Presentation Name
Course Name
Unit # – Lesson #.# – Lesson Name
General Tolerances
General tolerances are tolerances that are assumed if no specific tolerance is given for a dimension
Typically tolerances are specified based on the number of digits to the right of the decimal point in a dimension
Shown on drawing
Linear Dimensions
X.X = ± .020
X.XX = ± .010
X.XXX = ± .005
So, for example, using these general tolerances, a linear dimension specified with a precision of one digit to the right of the decimal point is specified to be manufactured within a variation of 0.02 larger or smaller than the specified dimension.
A part showing a specified length dimension of 3.64 must be manufactured to a length of between 3.63 and 3.65 (or equal to either of those values).
Angles = ± .5°

71. General Tolerances Tolerance = Upper Limit – Lower Limit
Presentation Name
Course Name
Unit # – Lesson #.# – Lesson Name
General Tolerances
Upper Limit = = 3.010
Lower Limit = =
For example, the depth of a part is specified to be 3.00 with no indication of tolerance associated with the dimension. Therefore, the general tolerances apply. Because the dimension has two digits places to the right of the decimal point, the bilateral tolerance of +/ applies. Therefore the upper limit is and the lower limit is This gives a tolerance of 0.020, the total allowed variation in the depth of the part.
Tolerance = Upper Limit – Lower Limit
0.10 = – = 0.020

72. Presentation Name
Course Name
Unit # – Lesson #.# – Lesson Name
Out of Tolerance
A manufactured part is said to be out of tolerance if the part is not within specified limits
Manufacturing facilities often institute quality control measures to help ensure that parts are within tolerance

73. Types of Fit
Clearance Fit limits the size of mating parts so that a clearance always results when mating parts are assembled
Interference Fit limits the size of mating parts so that an interference always results when mating parts are assembled
Transition fit occurs when two mating parts can sometimes have a clearance fit and sometimes have an interference fit

74. Presentation Name
Course Name
Unit # – Lesson #.# – Lesson Name
Types of Fit
Clearance Fit – Always a clearance between the axle and the opening
Here, the maximum size of the axle is 10 and the minimum size of the hole is If these parts are manufactured correctly, there will always be a clearance between these two parts when the axle is inserted through the hole.

75. Presentation Name
Course Name
Unit # – Lesson #.# – Lesson Name
Types of Fit
Interference Fit - Always an interference between the axle and the opening
In this case, the minimum size of the axle is 9.92, but the maximum size of the opening is Therefore, if the parts are manufactured correctly, the axle will always be larger than the opening. This type of fit may be called a press fit or force fit such that the two parts must be pressed together in order to assemble them.

76. Definitions
Maximum material condition (MMC) is the condition of a part when it contains the largest amount of material.
The MMC of an external feature, e.g., the length of a plate, is the upper limit of the dimension
The MMC of an internal feature, e.g., the diameter of a hole, is the lower limit of the dimension

77. Definitions
Least material condition (LMC) is the condition of a part when it contains the smallest amount of material.
The LMC of an external feature, e.g., the length of a plate, is the lower limit of the dimension
The LMC of an internal feature, e.g., the diameter of a hole, is the upper limit of the diameter dimension

78. Definitions
Allowance is the minimum clearance or maximum interference between parts
For a clearance fit, the allowance is the tightest possible fit between mating parts
Allowance = MMC internal feature
– MMC external feature

79. Calculate Allowance Allowance = MMC internal feature
Presentation Name
Course Name
Unit # – Lesson #.# – Lesson Name
Calculate Allowance
Allowance = MMC internal feature
– MMC external feature
Allowance = –
= 0.15
MMC
MMC
In the case of a clearance fit, the allowance is the smallest space between mating parts.
The maximum material condition (MMC) of the hole is since the smaller hole will result in the most material in the part
The maximum material condition (MMC) of the axle is since the larger axle will result in the most material in the part

80. Calculate Allowance Allowance = MMC internal feature
Presentation Name
Course Name
Unit # – Lesson #.# – Lesson Name
Calculate Allowance
Allowance = MMC internal feature
– MMC external feature
MMC internal feature
External feature
MMC
Allowance = –
= – 0.15
Have students calculate the allowance for this interference fit, then click to show the answer.
In the case of an interference fit, the allowance is negative and represents the maximum interference. In this case, the axle can be as much as 0.15 larger than the hole into which it fits. The larger the interference, the more difficult it is to force the axle into the hole.
The allowance, or maximum interference, is 0.15

81. A Note About Dimension Tolerance
Presentation Name
Course Name
Unit # – Lesson #.# – Lesson Name
A Note About Dimension Tolerance
In general, the more significant figures in the dimension, the tighter the tolerance
Overly precise dimensions and overly tight tolerances increase manufacturing costs
Specify dimensions only to the precision and tolerance necessary for the part to function properly
For example, specifying a tight tolerance , say +/ would be excessive and increase the cost of the coaster needlessly. However, specifying a tight tolerance on connections on an astronaut’s suit is necessary to ensure no leakage of gas.

82. Documentation Introduction to Engineering Design
© 2012 Project Lead The Way, Inc.

83. Documentation
Once a design has been approved and fully researched, the part needs to be prototyped or manufactured.
To do so, we need to have the appropriate documentation to communicate the idea to everyone in the company.
Documentation is the most difficult, time consuming, yet most important part of engineering communication.
This documentation is done with working drawings.

84. Working Drawings
Working drawings are a complete set of drawings that document how an object will be manufactured and assembled. Each set should include:
Part Drawings
Assembly Drawings
Parts List
Specifications or Instructions

85. Part Drawing
A part drawing is the drawing that contains all the information for making one part of the design.
This drawing consists of dimensioned orthographic views. If necessary, section, auxiliary, detail, and an isometric view can help document the part.
All features of the part will be dimensioned so that it can be manufactured.

86. Part Drawing Example

87. Title Blocks
Title blocks are necessary to identify the drawing and the general details that go along with that part. An example showing the parts of a title block are shown on the next slide.

88. © Project Lead The Way, Inc.
Title Blocks
Size of sheet. Important when reading a drawing to
ensure that the drawing is printed to display the
proper scale accurately. Also valuable when printing.
General notes and information. Located here
you will see information on fillet and rounds,
tolerances, and other general information that
would take up too much space on the drawing if
repeated on every feature.
Zoning is used to find specific locations on the
drawing. Usually shown in numbers and letters.
Example: ANSI Large style title block.
Title blocks can be customized by a company
but may contain the following information
Remember working drawings are made of many
different types of drawings. More than one sheet
usually goes with a design.
The drawing may be checked by Quality
Assurance to be sure that it meets all company
standards and requirements.
Title of the project, as opposed to a
specific part.
Name of person who checked the drawing. Just
like first drafts of papers written in English class,
drawings go through many revisions.
Another person will check the drawing and
approve the part for manufacture.
Documentation of how many times the drawing
has been changed.
Name of person who created the drawing.
Drawing number or specific part name in
relationship to the total design.
Scale of the part is important so that the reader
understands the relative size of the part.
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