engineering graphics a few highlights. see “a brief introduction to engineering graphics” in the...

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)

www.mcmaster.com

¼-20, RHMS, slotted, steel

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