1. Reading Technical Drawings
Foundations of Manufacturing

2. Dimensioning Systems
Four different systems of dimensioning used in U.S.
Fractional inch
Decimal inch
Dual dimensioning
SI Metric

3. Dimensioning Systems

4. Dimensioning Systems

5. Dimensioning Systems

6. Dimensioning Systems

7. Dimensioning Systems

8. Fractional type steel rules divided into units of:
1/16
1/32
1/64
Major graduation accentuated by longer lines
Some have small numbers printed adjacent to lines

9. Scale Reading Quiz 1
Record the scale length identified by 1
3/4

10. Scale Reading Quiz 1
Record the scale length identified by 2
1 5/8

11. Scale Reading Quiz 1
Record the scale length identified by 3
2 7/16

12. Scale Reading Quiz 1
Record the scale length identified by 4
3 3/16

13. Scale Reading Quiz 1
Record the scale length identified by 5
3 15/16

14. Decimal Scales Subdivided into units of 1/10, 1/20, 1/50, or 1/100 in.
1/50 is sufficient for most applications

15. Decimal Scales
Closer measurements require using micrometer, vernier or dial calipers
Major graduations are accented by longer lines-usually every 1/10 in.
Popular scales graduation style has .04 and .06 increments slightly longer than .02 and .08
Reads faster, more recognizable

16. Decimal Scales

17. Decimal Scales

18. Decimal Scales

19. Decimal Scales

20. Scale Reading Quiz 2
Record the scale length identified by... 1
.80

21. Scale Reading Quiz 2
Record the scale length identified by... 2
1.60

22. Scale Reading Quiz 2
Record the scale length identified by... 3
2.50

23. Scale Reading Quiz 2
Record the scale length identified by... 4
3.32

24. Scale Reading Quiz 2
Record the scale length identified by... 5
3.86

25. Decimal Dimensioning
Drawing may be dimensioned using two- or three-place decimals
Amount of tolerance is determined by number of decimal places

26. Decimal Dimensioning .50 may have tolerance of ± .01

27. Decimal Dimensioning
Converting fractions to decimals-results in too many decimal places
Need to round off those numbers to desired places

28. Decimal Dimensioning
Rule #1-When the figure following the last digit to be retained is greater than 5---increase the last number by one
.016 becomes .02
.047 becomes .05
.078 becomes .08

29. Decimal Dimensioning
Rule #2-When the figure following the last digit to be retained is less than 5---retain the last number
.031 becomes .03
.062 becomes .06
.093 becomes .09

30. Decimal Dimensioning
Rule #3-When the figure following the last digit to be retained is exactly 5 and the figure to be retained is odd---increase the last number by one
.375 becomes .38
.875 becomes .88

31. Decimal Dimensioning
Rule #4-When the figure following the last digit to be retained is exactly 5 and the figure to be retained is even---retain the last number
.125 becomes .12
.625 becomes .62

32. Decimal Dimensioning

33. Decimal Rounding Quiz .11 .12 .16 .23 .44 .55 .56 .109 = .125 = .156 =
.234 =
.438 =
.547 =
.562 =
.11
.12
.16
.23
.44
.55
.56

34. Decimal Rounding Quiz .64 .641 = .797 = .875 = 1.056 = 1.672 = 2.205 =
2.454 =
.80
.88
1.06
1.67
2.20
2.45

35. Decimal Rounding Quiz 3.335 = 3.767 = 5.555 = 6.665 = 7.045 = 8.885 =
3.34
3.77
5.56
6.66
7.04
8.88

36. Metric Dimensioning Metric increment of measure is millimeter
Will be noted if different
Convert a metric dimension to inches by multiplying it by

37. Metric Dimensioning
Conversion charts are available to provide converted dimensions
Metric scales are available and can be used-eliminating need for conversion

38. Metric Dimensioning Metric scales
Have graduations every millimeter of half-millimeter
Designated “mm” or “1/2 mm”
Every fifth millimeter is accentuated by a longer line
Every tenth millimeter is identified by a number

39. Metric Dimensioning

40. Scale Reading Quiz 3
Record the scale length identified by 1
20 mm

41. Scale Reading Quiz 3
Record the scale length identified by 2
35 mm

42. Scale Reading Quiz 3
Record the scale length identified by 3
51 mm

43. Scale Reading Quiz 3
Record the scale length identified by 4
77.5 mm

44. Scale Reading Quiz 3
Record the scale length identified by 5
93.5 mm

45. Blueprints Blueprinting-Term can be interpreted as
Drawing
Picture
Contains information
Required sizes
Tolerances
Essential requirements
Notes and instructions

46. Engineering Drawings Original drawing made by drafter or engineer
Prints are referred to as engineering drawings
Also referred to as blueprints (more common term)

47. Engineering Drawings Standardized drawings “A” size is 8 ½ x 11 inches
“B” size is 11 x 17 inches
“C” size is 17 x 22 inches
“D” size is 22 x 34 inches
“E” size is 34 x 44 inches

48. Engineering Drawings

49. Title Blocks Each drawing contains a Title Block
Drawing number is most prominent lettering in title block
Lettered larger to stand out
Scale determines the size of the object drafted

50. Title Blocks Mechanical drawings may be reduced to Half size
Quarter size
One eighth size

51. Title Blocks Mechanical drawings may be enlarged Double Four times
Ten times

52. Title Blocks Half scale---1/2, 1:2, or ½”=1”
Twice scale-2/1, 2:1, 2-1, 2”=1” or 2X
Arrangement of numerals indicates relationship

53. Title Blocks Refer to scale as the “Do Scale”
“D” stands for the drawing
“O” stands for the object
Sale of 1:2 means
The drawing is 1 inch
Object is 2 inches
A “Do Scale” of 2:1 means
The drawing is 2 inches
The object is one inch or one half the drawing size

54. Title Blocks

55. Title Blocks

56. Title Blocks

57. Title Blocks

58. Drawing Notes Local notes-apply to specific item or area
Use leaders
Direct notes to point of application
General notes apply to whole drawing or product
Machining
Heat treat
Material
Tolerances

59. Drawing Notes
Abbreviations are used in notes
Keep them brief

60. Drawing Notes-General (Example)
UNLESS OTHERWISE SPECIFIED
METRIC UNITS ARE MILLIMETERS
FILS & RNDS ARE .12R
PART SYM ABOUT CL

61. Single-View Drawings Sometimes adequate to describe object
Material thickness is listed

62. Detail Drawings
“Production drawings” and “working drawings” are general terms
Includes all types of engineering drawings

63. Detail Drawings Detail drawings include Sufficient number of views
Dimensions
Notes
Other pertinent information

64. Centerlines

65. Centerlines Intersecting centerlines drawn through each hole
Used for location-centerlines are extended outside view and dimensions are added
Radii are the same-often share a common axis-common design practice

67. Diameters and Radii

68. Diameters and Radii  Internationally recognized symbol for diameter
Use in place of the abbreviation DIA
Number of holes indicated

69. Diameters and Radii Overall dimensions can be calculated
Remaining material around hole can be calculated

70. Diameters and Radii
Remaining material around hole can be calculated

71. Break Lines Permits removal of a portion of view Paper size is smaller
Drawing scale can get smaller
Portion removed must be uniform in shape

72. Break Lines
Drawing is full size and does not require a “B” size drawing

73. Break Lines

74. Cylindrical Break

75. Short Break

76. Long Break

77. Typical Dimensions Entered after a dimension
Means all other similar dimensions are same as one marked “TYP”
Eliminates repetition of dimensions
Saves on drawing space

78. Symmetry Indicated by note
Indicated by view’s centerline carrying abbreviation

79. Thermostat Gasket
1. What is the part number?
11A001

80. Thermostat Gasket
2. What is the name of the part?
Thermostat gasket

81. Thermostat Gasket
3. What is the drawing size? (A, B, or C) A

82. Thermostat Gasket
4. What scale is the drawing?
1:1

83. Thermostat Gasket 5. Use words to explain the answer to question 4.
Actual size

84. Thermostat Gasket
6. How thick is the part?
.06

85. Thermostat Gasket
7. Is the part symmetrical?
Yes

86. Thermostat Gasket
8. Which system of dimensioning was used? (Refer to page 21.)
Decimal

87. Thermostat Gasket
9. What is the fractional equivalent of the center hole size?
2 3/16

88. Thermostat Gasket
What is the fractional equivalent of the mounting hole spacing? (Refer to the equivalency chart, page 25.)
3 5/8

89. Thermostat Gasket
11. Calculate the longest overall dimension of the part.
4.24

90. Thermostat Gasket
12. Calculate the overall dimension of the part (height.)
2.88

91. Thermostat Gasket
13. Calculate the material remaining between the large hole and the nearest outside edge.
.345

92. Thermostat Gasket
14. Calculate the material remaining between the small hole and the nearest outside edge.
.155

93. Thermostat Gasket
15. Calculate the material remaining between the large hole and the nearest small hole.
.56