1. Engineering Graphics A few highlights
Slides for a 60 min highlight lecture. Slides drawn from engg graphics.pptx, also posted as a pdf on ME2011 graphics resource site. Note: make edits to engg graphics.pptx, and then copy slides to here.

2. See “A Brief Introduction to Engineering Graphics” in the Resources section of the ME2011 web site See Q01 on the Assignments page for what you need to know for the graphics quiz

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. 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”

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

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

7. FRONT
5 mistakes
CORRECT DRAWING
FIND THE MISTAKES!

8. CORRECT DRAWING

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

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

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

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

13. Find The Mistakes!
AT least 8 mistakes

14. 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.

15. 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

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

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

18. 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
What if A was 3.9 in width?

19.
Browse to materials > metals > aluminum > bar/sheet stock > 6061 > .25” thick > 12” long.

20. 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.

21. Example

24. Highlight holes and notes

25. 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.

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

27. Representing tolerances

28. 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

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

30. .623 .626 .622 .625 Holes and shafts hole shaft
Will all shafts fit into all holes?
A = yes, B = no
What is maximum clearance?
A = .001, B = .002, C = .003, D = .004
Holes and shafts
hole
shaft
.626
.625
.623
.622
Will this shaft always fit in this hole? Ans = yes
What is max/min clearance? Ans = ( )/2
.623
.622
.626
.625

31. { 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

32. Geometric Dimensioning and Tolerancing (GD&T)

33. 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?

34. 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

35. 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

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

37. 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

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

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

40.
¼-20, RHMS, slotted, steel

41. Name the Fastener:
Socket Head Cap Screws

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

44. Phillips Flat Head Screw with countersink

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

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

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

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

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