1. A Brief Introduction to Engineering Graphics
This set of slides is designed to be read as a graphics resource. Can take excerpts for presentations.
Bring: fastener/tools examples,, big real engineering drawing, an object to spin, LEGOs for tolerance section, collection of shafts and holes for tolerancing,
See Notes pages
10/2011 Add: Get sample of a real engg dwg from Toro, Tennant. Along with photos of the part.
10/2009 Add: Types of drawings (detail, assembly, exploded view assembly, BOM; see Meyer et al., Technical Graphics, Chapter 9). For required text, consider Technical Graphics, Meyer et al. See lecture notes for OSU course
10/2007 Add: tolerance stackup; show a part w/ pin mating with a hole…and all the things that could go wrong; offset section. Add features sections. Add material on hole and threading types.
Intro: Eng graphics important for meche students to know…but not intellectually demanding. Basics here, details in any eng graphics text.
Will Durfee & Tim Kowalewski
Department of Mechanical Engineering
University of Minnesota

2. Opening comments
Engineering graphics is the method for documenting a design
Mechanical engineering students must be familiar with standards of engineering graphics as it is expected in industry
This set of slides introduces some of the basics, but is not comprehensive
For more, see
Engineering Graphics section on the Resources page of the course ME2011 website
Any engineering graphics textbook

3. Documenting a part requires...
1. SHAPE
2. SIZE
3. MATERIAL
4. TOLERANCE
5. FINISH
To fully document a part requires all of these
What are examples?

4. Engineering drawings Universal language
Conventions (drawing grammar) simplify communication; your drawing is at risk if you defy
CAD packages make formal drawing easy…if you follow the conventions
The machinist will laugh at you behind your back if you show up with a non-standard drawing
Graphics is all about how to transmit this info using the conventional language.
Buck these conventions at your peril…The machinist will laugh at you and your boss will relegate you to fetching coffee
CAD packages automate this. Nobody uses a T-square and pencil any more

5. Multiview drawings Top Right Front TOP RIGHT SIDE FRONT
Views must line up
Multi-view is an artifact of the 2-D world. Perhaps in 25 years it will be gone. But for now, you must know
This is 3rd angle projection, the “unfolding the box” or “you walk around to the right side”.
Rest of world uses 1st angle projection where the right side view would be to the left of the front view. “Roll the object on its edge” or “you stay still and the object rotates”.
See Betroline for details.
RIGHT SIDE
FRONT
“3rd angle projection”

6. Multiview drawings Top Right Front TOP RIGHT SIDE FRONT
Views MUST align
Views must line up
Multi-view is an artifact of the 2-D world. Perhaps in 25 years it will be gone. But for now, you must know
This is 3rd angle projection, the “unfolding the box” or “you walk around to the right side”.
Rest of world uses 1st angle projection where the right side view would be to the left of the front view. “Roll the object on its edge” or “you stay still and the object rotates”.
See Betroline for details.
RIGHT SIDE
FRONT
“3rd angle projection”

7. Multiview drawings Top Right Front TOP RIGHT SIDE FRONT
Views MUST align
Views must line up
Multi-view is an artifact of the 2-D world. Perhaps in 25 years it will be gone. But for now, you must know
This is 3rd angle projection, the “unfolding the box” or “you walk around to the right side”.
Rest of world uses 1st angle projection where the right side view would be to the left of the front view. “Roll the object on its edge” or “you stay still and the object rotates”.
See Betroline for details.
RIGHT SIDE
FRONT
Rotate the part
to the right (Europe)
“3rd angle projection”
You walk around
part to the right (US)

8. The Glass Box:
Bertoline, Engineering Graphics

9. Alignment & Orientation are preserved…
Bertoline, Engineering Graphics

10. Six Principle views: obey layout
Great way to get relegated to making coffee.

11. Basic lines (the “alphabet of lines”)
Object line
Hidden line
Center line
The “alphabet of lines”
ANSI standards for these
Dimension line

12. HIDDEN LINES
Show internal features or holes

13. CENTER LINES
Long-short dashed lines showing lines of symmetry and axes of cylinders and holes

14. Interpreting Center Lines
Long-short dashed lines showing lines of symmetry and axes of cylinders and holes
Enough Info?
Enough Info?

15. COULD BE THIS...
Be careful when interpreting center lines. Do not assume axial symmetry

16. Centerlines imply symmetry,
OR THIS
Centerlines imply symmetry,
NOT revolution per se

17. HERE, ONLY 2 VIEWS NEEDED (Correct drawing)
If circularly symmetric, drawing should tell you. If it is circularly symmetric, only need 2 views.

18. Find The Mistakes!
AT least 8 mistakes

19. Find The Mistakes!
Top view not on top; inside circle in top view not solid
Bottom view not on bottom
Hidden line used instead of center line
Centerline in right view does not extend beyond part;
Right view not aligned correctly
More views than necessary
No additional info like dimensions, materials, etc.

20. FRONT
Here’s a 3-D object that has to be represented in a set of 2-D drawings. One must be careful about the conversion.

21. FRONT
5 mistakes
CORRECT DRAWING
FIND THE MISTAKES!

22. CORRECT DRAWING

23. SECTIONS A
Use sections for showing complex internal shapes where hidden lines would be confusing
Slice through the object (the cutting plane)
Hatch cut material (exposed surfaces)
<…add offset sections…>
YES NO

24. Working with person sitting next to you copy this and
Now draw this,
How many disagree?
Working with person sitting next to you copy this and
draw the TOP VIEW

25. Working with person sitting next to you copy this and
Possible Geometries
Now draw this,
How many disagree?
Working with person sitting next to you copy this and
draw the TOP VIEW

26. Working with person sitting next to you, sketch the Section View
How many disagree?
Bring samples up to front
Working with person sitting next to you, sketch the Section View

27. OK OK Correct Section Views How many disagree?
Bring samples up to front
Correct Section Views

28. Working with person sitting next to you, Find the MISTAKES
Wrong
Wrong
How many disagree?
Bring samples up to front
Working with person sitting next to you, Find the MISTAKES

29. Working with person sitting next to you, sketch the Section View
How many disagree?
Bring samples up to front
Working with person sitting next to you, sketch the Section View

30. REVOLVED SECTION Preferred “True” section
For revolved sections, hole pattern symmetric (convention)
Preferred
“True” section

31. DIMENSIONING 1. SHAPE 2. SIZE 3. MATERIAL 4. TOLERANCE AND FINISH
Reference: Bertoline, Chapter 4

32. Dimensioning Conventions exist for choice and placement
Not too many and not too few
Never should measure off drawing with a ruler 5 5 3
Adds *size* to object
W/ CAD, natural part of part creation.
W/ traditional drafting, added later
Conventions for CHOICE, PLACEMENT
Leave nothing to chance. Machinist should not be taking dimensions off your dwg with a ruler 3

33. Under/Over Dimensioning3 5 3 5 2
Leave nothing to chance.
Do not over dimension, do not under dimension

34. Dimensioning rules: …find the mistakes.3 5 3 5 2
Leave nothing to chance.
Do not over dimension, do not under dimension

35. Dimensioning guidelines3 5
1. Don’t overdefine or underdefine the object. [MOST IMPORTANT]
2. Dimension to the visible contour or shape of the feature / Don’t dimension to hidden lines.
4. Don’t dimension to object lines (model edges), use extension lines.
5. Don’t overlap a dimension and the model. Place dimensions away
from the model’s surface.
6. Don’t cross extension lines if possible.
7. Group dimensions when possible unless it become difficult to read.
8. Place dimensions on the side of the view were adjacent views exist
(for easy referencing).
Leave nothing to chance.
Do not over dimension, do not under dimension 3 5 2

36. Design Detail ½” thick aluminum block
Which is more expensive: A or B and why?
6.0 A
6.0 B
B is not standard stock, way more expensive.
In same vein, use standard fasteners
4.0
4.1

37.
Browse to materials > metals > aluminum > bar/sheet stock > 6061 > .50” thick > 6” long.

38. Dimensioning Choices & Design Intent
If change width of block to 8, what happens to the hole location? A B 6 2 6 4 2
If change width to 8 inches, does hole move?
Think *carefully* about design intent before picking a dimensioning scheme.
With CAD, wrong dimensioning scheme is a major pain to correct.

39. Placement conventions
Extension and dimension lines thinner than object lines
Dimensions legible but not dominate
See Leuptow pp for conventions

40. Lettering: 1 or 2 directions onlyOK OK NO

41. Extension Lines
No gaps when crossing object lines to dimension internal features
OK to cross extension lines
Pro/E automates this

42. All on one side
YES NO

43. Dimensioning Rounds Place dimension on view that shows the circle
0.25
0.75
R 0.125
Put dimension on view that shows the circle.
Show diameter, unless other considerations dictate radius
Place dimension on view that shows the circle
Show diameter rather than radius

44. Highlight holes and notes

45. TOLERANCES
Reference: Bertoline, Chapter 4. Strongly suggest reading this chapter.
Tolerances matter because it is rare that you can sit there and custom fit parts. For modern assembly, every instance of Part A must fit into every instance of Part B or else you will have a problem assembling.
It is impossible to make things to an exact dimension. All mfg processes will give you a range about the nominal dimension. The more you pay, the tighter the range.
For example, the outside dimensions of a block may not matter so much (tol = 0.1), but the diameter of the hole in that block matters a lot because it receives a press fit bearing (tol = tenths)
A ½ inch hole made on an ordinary drill press gives you a hole in the range to (+/ ). For higher precision, drill undersize and use a reamer…but it will cost you more and take longer to fabricate.
Moral: Go with the loosest tolerance you can.

46. Tolerances Matter because parts cannot be made to an exact dimension
Must specify dimension tolerance so that every part A fits every part B
Higher tolerance = higher cost
A ½ inch hole made on an ordinary drill press gives you a hole in the range to (+/ ). For higher precision, drill undersize and use a reamer…but it will cost you more and take longer to fabricate.

47. ½ inch drill bit: +/- .0040 ½ inch reamer: +.0003, -.0000
For low tolerance, drill undersize and follow with reamer
½ inch reamer: ,

48. LEGOS !
ABS plastic
You can combine six 8-stud bricks of the same color 102,981,500 different ways
91% of all households with children in Denmark own LEGO products
During the period , 110,000,000,000 (110 billion) LEGO elements were molded
Bayer Corporation's Polymers Division is the official supplier of ABS plastic to the LEGO group.
Exact specifications of the Bayer resin supplied to the LEGO Group are a closely held secret.
Dimension tolerance of mold is mm ( inch)!
Bayer Corporation's Polymers Division is the official supplier of ABS plastic to the LEGO group.
LEGO bricks are one of the most demanding ABS applications
Mold tolerance is five thousandths of a millimeter (0.005 mm) or two tenths ( in.) in English units
Most molds are held to in. (one thou) in. Lego dimensions are five times more accurate.
Molds for LEGO pieces are made in a factory in Germany and two factories in Switzerland
Exact specifications of the Bayer resin supplied to the LEGO Group are a closely held secret.
ABS resin not only offers (1) tight dimensional stability required for molding to narrow tolerances, (2) flow rate, (3) impact resistance, (4) surface appearance, (5) anti-static properties, (6) no long-term creep, (7) nonflammable, (8) non-toxic.
9.6
1.7 8
D 5

49. Representing tolerances

50. Tolerance stack-up ? 14.75 15.25 3.0 ± .05 5 high stack
What is min and max height of stack? ?
3.0 ± .05
5 high stack

51. Tolerance Stacking What’s the tolerance (+/-) on dimension x?
Microphone hot-potato
What’s the tolerance (+/-) on dimension x?
Ans: +/- 0.3

52. Chain or Baseline Dimensioning? … You decide
Choice of dimensions from “Design Intent”
Reference or “datum” dimensioning compatible with CAM. Here, left edge is a datum.
Watch out for tolerance stackup

53. Chain or Baseline Dimensioning
Choice of dimensions from “Design Intent”
Reference or “datum” dimensioning compatible with CAM. Here, left edge is a datum.
Watch out for tolerance stackup

54. .623 .626 .622 .625 Holes and shafts hole shaft
Will all shafts fit into all holes?
What is maximum clearance?
hole
shaft
.626
.625
.623
.622
Will this shaft always fit in this hole?
What is max/min clearance?
.623
.622
.626
.625

55. ANSI standards for shaft & holes
Clearance
Shaft smaller than hole for all shafts and holes
Interference
Shaft larger than hole for all shafts and holes
Transition
Smallest shaft fits in largest hole
Running/Sliding
RC1 (fit together, no play) to RC9 (fit loosely)
Force/shrink
FN1 (light drive and pressure) to FN5 (high stresses and pressures)
…and others
Like Locational, etc.
“How loose should it be?”
Much has been worked out in past. Use it.
Consult machinery handbook or drafting handbook for details
Basic hole
Use nominal size of hole as starting point
Basic shaft
Use nominal size of shaft as starting point

56. Preferred Fit Example…

57. “Basic Hole” Tolerancing Example
1.0000
Smallest hole & largest shaft:
– = clearance
Largest hole, smallest shaft
– = clearance
Drawing shows 1 in. nominal, ANSI RC4 clearance fit
“Basic Hole” means smallest possible hole = nominal, then size shaft for clearance
RC4 clearance = [0.0008, ] = [smallest hole-largest shaft,
largest hole - smallest shaft]

58. Title block information for tolerance
ALL DIMENSIONS IN INCHES
HOLD ALL DIMENSIONS TO ± UNLESS SPECIFIED
4.250 = good to +/- .001
4.25 = good to +/- .01
4.3 = good to +/- .1
Dimension Tolerance
X.X ± 0.1
X.XX ± 0.05
X.XXX ± 0.001

59. { Design Detail Bent aluminum sheet, 1/16” thick
A or B: Which is more expensive and why? A B
4.0 + -
0.003
0.030 {
A. Punch shape & holes, then bend ===> cheap
Press = $100/hr, parts/hr
B. Bend then drill ==> expensive
$0.50 per hole
Work with mfg (even for prototype) to reduce cost

60. Tolerance vs. Cost $ $$ $$$$ 1.00 ±.075 1.00 ±.05 1.000 ±.005
±.00005

61. Manufacturing Tolerances

62. Geometric Dimensioning and Tolerancing (GD&T)

63. Traditional tolerancing is ambiguous
3.000
±.005
1.000 ±.005 ? ?
Can left side be .995 and right side be 1.005?
Can part be .995 at edges and in middle and thus not sit flat on a table?

64. Ambiguity… + + Square deviation Circular deviation .25 ± .01
Hole location defines an error *square*, but we really want to allow a *circular* deviation
Solved by the “Geometric Dimensioning and Tolerancing System” that allows you to specify design intent. Based on showing nominal dimensions augmented with a notation system for showing design intent for tolerances.
More?: See Chapter 6 in Lueptow + +
Square deviation
Circular deviation

65. Geometric Dimensioning and Tolerancing
.125 +/- .002
.01
.25
Ideal position of hole is marked with box; the “true-position dimension”; no +/- notation.
Feature control box shows how close hole is to exact; within circular tolerance zone with diameter .01
Ideal position of hole. .25, is marked with box and no +/- notation.
Feature control box shows how close hole is to exact; within circular tolerance zone with diameter .01

66. Geometric Dimensioning and Tolerancing
.25

67. GD&T Resources https://sites.google.com/a/u mn.edu/me2011/resources
ME2011 website:
mn.edu/me2011/resources
Efunda tutorial:
signstandards/gdt

68. What they are and how to indicate on a drawing
Threaded Fasteners
What they are and how to indicate on a drawing

69. Threaded Fasteners Holes Threads Threaded fasteners
Bertoline references:
Holes: Fig. 4.55, Sec. 8.3, Fig. 8.32, 8.37
Threads: Sect. 9.3, Fig. 9.33, 9.34
Threaded fasteners: Sect
Fillets, rounds, chamfers: Sect. 9.6, Fig. 9.52
Bearings: Sect 9.7.4
Gears: Sect 9.7.1, Fig

70. Holes 19 DRILL – 0.75 DEEP or O .166 . 75 DEPTH 0.75 REF
Pix from unless noted

71. Thru holes
19 DRILL – THRU or
O .166

72. Threads

73. Threaded Fasteners (screws, bolts)
Specify diameter, thread, length, head
1/4" DIA
1/4-20 x 1, RHMS
20 THREADS
PER INCH
1" LONG
ROUND HEAD MACHINE SCREW

74. Common screw thread sizes Unified Thread Standard
2-56
4-40
6-32
8-32
10-24
1/4-20
3/8-16
1/2-13
5/8-11
3/4-10
DIA. = (N*.013) (inches)

75. Alternate Thread Callout

76. Head shapes Cap screw Pan Socket head cap screw (SHCS) Set screw Flat
Round

77. Driving a fastener
Slotted
Phillips
Torx
Hex cap
Hex head
(Allen head)

78. McMaster-Carr

79. Name the Fastener:
Socket Head Cap Screws

80. Name the Fastener: Socket Head Cap Screw Socket Head Cap Screw
with counterbore
Socket Head Cap Screws

82. Socket Head
Cap Screw with counterbore
Phillips Flat Head Screw with countersink

84. Set Screw
Countersunk,
Phillips Flat head

85. Convention for screws
“SCHEMATIC”
“SIMPLIFIED”

86. Convention for threaded holes
6-32 THRU
TOP
FRONT
FRONT SECTION

87. Blind threaded holes 1/2 – 13 x 1.325 DEEP .4219 1.50 1/2 – 13 1.325
/2 –
THREAD DEPTH
DRILL DEPTH

88. Countersunk holes
.562 – 82O CSK,
x 82O

89. Counterbored holes
19 DRILL – 29 CBORE, 14 DEEP
C-BORE DEPTH

91. Other Items for Drawings

92. Leaders & notes To annotate dwg with notes useful to machinist NOTE B
Can also refer to a notes section at bottom of page
NOTE B

93. TITLE BLOCKS Basic Optional Follow your company standards Title Name
Date
Units
Optional
Company name, sheet number, scale, tolerances, material, finish....
Follow your company standards

94. ALL DIMENSIONS IN INCHES
Basic
Title
Name
Date
Optional
Company name, sheet number, scale, tolerances, material, finish....
Follow ANSI or company standards
For Pro/E, what are your units?
A basic title block
MY PART
W. DURFEE /2/2014
ALL DIMENSIONS IN INCHES

95. A title block with more information

96. A title block using a company template

97. Production Drawings Many types of drawings can be produced from
the CAD database
ASSEMBLY
SKETCHES
MODEL
SKETCHES
SKETCHES
DETAIL
DETAIL
DETAIL
DETAIL
DETAIL
BOM
MANUALS
MFG PROCESS