Engineering GraphicsA 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
1. SHAPE
2. SIZE
3. MATERIAL
4. TOLERANCE
5. FINISH
Documenting a part requires...
Multiview drawings
FRONT RIGHT SIDE
TOP
“3rd angle projection”
Six Principle views: obey layout
Basic lines (the “alphabet of lines”)
Object line
Hidden line
Center line
Dimension line
FIND THE MISTAKES!
FRONT
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. SIZE3. MATERIAL4. TOLERANCE AND FINISH
Dimensioning rules:…find the mistakes.
3
5
5
3
5
3
5
2
Design Detail½” thick aluminum blockWhich is more expensive: A or B and why?
4.0 4.1
A B
6.0 6.0
What if A was 3.9 in width?
www.mcmaster.com
Dimensioning Choices & Design Intent
6
2
2
6
6
4
2
6
A B
If change width of block to 8, what happens to the hole location?
Example
TOLERANCES
www.efunda.com/processes/machining/drill_press.cfm
www.efunda.com/processes/machining/drill.cfm
½ inch drill bit: +/- .0040
½ inch reamer: +.0003, -.0000
Representing tolerances
3.000
1.000
3.0052.995
1.005.995
3.000±.005
1.000±.005
3.000+.005-.005
1.000+.005-.005
Tolerance stack-up
3.0 ± .05 5 high stack
?14.7515.25
What is min and max height of stack?
Tolerance Stacking
What’s the tolerance (+/-) on dimension x? Ans: +/- 0.3
Holes and shafts
.626
.625.623.622
holeshaft
.626
.625.623.622
1. Will all shafts fit into all holes?
A = yes, B = no
2. What is maximum clearance?
A = .001, B = .002, C = .003, D = .004
Design DetailBent aluminum sheet, 1/16” thickA or B: Which is more expensive and why?
A
B4.0 +-
0.003
0.030{
Geometric Dimensioning and Tolerancing (GD&T)
Traditional tolerancing is ambiguous
3.000±.005
1.000 ±.005
? ?
Ambiguity…
.25 ± .01
.25 ± .01
+ +
Square deviation Circular deviation
Geometric Dimensioning and Tolerancing
.25
.125 +/- .002
.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
Threaded FastenersWhat they are and how to indicate on a drawing
Threaded Fasteners (screws, bolts)
• Specify diameter, thread, length, head
1/4-20 x 1, RHMS
ROUND HEADMACHINE SCREW1" LONG
20 THREADSPER INCH
1/4" DIA
Head shapes
Pan
Flat
Round
Cap screw
Socket head cap screw (SHCS)
Set screw
Driving a fastener
Slotted
Phillips
Torx
Hex cap
Hex head(Allen head)
Name the Fastener:
Name the Fastener:
Socket Head Cap Screw
Socket Head Cap Screwwith counterbore
Phillips Flat Head Screw with countersink
Holes
DEPTH0.75 REF
19 DRILL – 0.75 DEEPor
O .166 . 75
Pix from www.mcmaster.comunless noted
Convention for threaded holes
FRONT
TOP
FRONTSECTION
6-32 THRU
Blind threaded holes
1/2 – 13 x 1.325 DEEP
THREAD DEPTH
DRILL DEPTH
.4219 1.501/2 – 13 1.325
Countersunk holes
.562 – 82O CSK, 1.125
.562 1.125 x 82O
Counterbored holes
19 DRILL – 29 CBORE, 14 DEEP
C-BORE DEPTH
19 29 14