Engineering Graphics
A few highlights
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
Documenting a part requires...
1. SHAPE
2. SIZE
3. MATERIAL
4. TOLERANCE
5. FINISH
Multiview drawings
TOP
FRONT
RIGHT
SIDE
“3rd angle projection”
Six Principle views: obey layout
Basic lines (the “alphabet of lines”)
Object line
Hidden line
Center line
Dimension line
FRONT
FIND THE MISTAKES!
CORRECT DRAWING
Interpreting Center Lines
Enough Info?
Enough Info?
COULD BE THIS...
OR THIS
Centerlines imply symmetry,
NOT revolution per se
HERE, ONLY 2 VIEWS NEEDED
(Correct drawing)
Find The Mistakes!
Find The Mistakes!
SECTIONS
A
A
YES
NO
DIMENSIONING
1.
SHAPE
2. SIZE
3.
4.
MATERIAL
TOLERANCE AND FINISH
Dimensioning rules:
…find the mistakes.
5
5
2
3
3
3
5
5
Design Detail
½” thick aluminum block
Which is more expensive: A or B and why?
A
6.0
B
6.0
4.0
4.1
What if A was 3.9 in width?
www.mcmaster.com
Dimensioning Choices & Design Intent
If change width of block to 8, what happens to the hole location?
A
B
6
6
2
4
2
2
6
6
Example
TOLERANCES
www.efunda.com/processes/machining/drill.cfm
www.efunda.com/processes/machining/drill_press.cfm
½ inch drill bit: +/- .0040
½ inch reamer: +.0003, -.0000
Representing tolerances
1.005
.995
1.000
3.005
2.995
3.000
+.005
1.000 -.005
+.005
3.000 -.005
1.000 ±.005
3.000 ±.005
Tolerance stack-up
What is min and max height of
stack?
14.75
15.25
?
3.0  .05
5 high stack
Tolerance Stacking
What’s the tolerance (+/-) on dimension x?
Ans: +/- 0.3
1.
Holes and shafts
Will all shafts fit into all holes?
A = yes, B = no
2.
What is maximum clearance?
A = .001, B = .002,
C = .003, D = .004
hole
shaft
.626
.625
.626
.625
.623
.622
.623
.622
Design Detail
Bent aluminum sheet, 1/16” thick
A or B: Which is more expensive and why?
4.0 +-
{
0.030
A
0.003
B
Geometric Dimensioning and
Tolerancing (GD&T)
Traditional tolerancing is ambiguous
1.000 ±.005
3.000 ±.005
?
?
Ambiguity…
.25 ± .01
.25 ± .01
+
+
Square deviation
Circular deviation
Geometric Dimensioning and Tolerancing
.125 +/- .002
.01
.25
•
•
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
Threaded Fasteners
What they are and how to indicate on a drawing
Threaded Fasteners (screws, bolts)
• Specify diameter,
thread, length, head
1/4-20 x 1, RHMS
1/4" DIA
1" LONG
20 THREADS
PER INCH
ROUND HEAD
MACHINE SCREW
Head shapes
Cap screw
Pan
Flat
Round
Socket head
cap screw
(SHCS)
Set screw
Driving a fastener
Slotted
Hex cap
Phillips
Torx
Hex head
(Allen head)
www.mcmaster.com
¼-20, RHMS, slotted, steel
Name the Fastener:
Name the Fastener:
Socket Head
Cap Screw
Socket Head
Cap Screw
with counterbore
Phillips Flat
Head Screw
with
countersink
Holes
19 DRILL – 0.75 DEEP
or
O .166
. 75
DEPTH
0.75 REF
Pix from www.mcmaster.com
unless noted
Convention for threaded holes
6-32 THRU
TOP
FRONT
FRONT
SECTION
Blind threaded holes
1/2 – 13 x 1.325 DEEP
.4219 1.50
1/2 – 13 1.325
THREAD DEPTH
DRILL DEPTH
Countersunk holes
.562 – 82O CSK,
1.125
.562
1.125 x 82O
Counterbored holes
19 DRILL – 29 CBORE, 14 DEEP
19
29
C-BORE DEPTH
14