technical graphics overview - my smcc

Technical Graphics Overview

Dan AbbottSouthern Maine Technical College

[email protected]

207 741-5564

mailto:[email protected]

Poorly Applied Standards (Real Drawing)

Well Applied Standards

Units and Scale

Rules for Calculations

1. Always use exact conversions NOT rounded or soft

conversions.

a. One inch is equal to exactly 25.4 millimeters

b. One foot is equal to exactly .3048 meters

2. Always include units in all calculations and cancel them

as you go.

1. 1IN = 25.4 mm/IN

2. 1ft = .3048 m/ft

Standard Measurement in U.S. is

Metric and Decimal Inch

•The U.S. officially adopted the metric system in

1866.

•U.S. customary units are defined by their metric

equivalents.

•The foot is legally defined to be exactly 0.3048

meter, making one inch exactly 25.4 millimeters.

•The pound is legally defined to equal exactly

453.59237 grams.

Metric – Length

Length

The standard unit of length in the metric

system is the meter. Other units of length and

their equivalents in meters are as follows:

1 millimeter = 0.001 meter

1 centimeter = 0.01 meter

1 decimeter = 0.1 meter

1 kilometer = 1000 meters

Metric – Length Symbols

1 millimeter = 1 mm

1 centimeter = 1 cm

1 meter = 1 m

1 decimeter = 1 dm

1 kilometer = 1 km

Metric – Length Reference

•1 meter is a little longer than 1 yard or 3 feet

•It is about half the height of a tall adult

•A centimeter is nearly the diameter of a dime

•A millimeter is about the thickness of a dime

•A half inch wrench falls between a 12 mm

and a 13 mm wrench.

Metric – Volume

The standard unit of volume in the metric

system is the liter. One liter is equal to 1000

cubic centimeters in volume.

1 milliliter = 0.001 liter

1 centiliter = 0.01 liter

1 deciliter = 0.1 liter

1 kiloliter = 1000 liters

Metric – Volume

1000 milliliters equals 1 liter

1 milliliter equals 1 cubic centimeter

1 milliliter = 1 ml

1 centiliter = 1 cl

1 deciliter = 1 dl

1 liter = 1 l

1 kiloliter = 1 kl

Metric – Volume Reference

For reference,

One liter is a little more than 1 quart

One Gallon is a little less than 4 liters

One teaspoon equals about 5 milliliters

Metric – Temperature

Temperature

•Temperature is expressed in degrees Celsius.

•Water (sea level) boils at 100°Celsius (100°C)

•Water (sea level) freezes at 0° Celsius (0°C)

•(9/5) * X°C+32 = X°F

•(5/9) * (X°F-32) = X°C

Metric – Temperature

Temperature (9/5 = 1.8)

•(1.8 * X°C)+32 = X°F

•30°C = (1.8 * 30) + 32 = 86°F

•10°C = (1.8 * 10) + 32 = 50°F

Temperature (5/9 ~ .556)

•0.55 * (X°F-32) = X°C

•100°F = 0.556 * (68) ~ 38°C

•-30°F = 0.556 * (-62) ~ 34°C

Prefixes Multiplier

Conversion to meters:

•milli- 0.001 1mm = 0.001m

•centi- 0.01 1cm = 0.01m

•deci- 0.1 1dm = 0.01m

•deka- 10 1dam = 10m

•hecto- 100 1hm = 100m

•kilo- 1000 1km = 1000m

Prefixes Multiplier

•1 meter converted:

•milli- 0.001 1m = 1000mm

•centi- 0.01 1m = 100cm

•deci- 0.1 1m = 10dm

•deka- 10 1m = 0.1dam

•hecto- 100 1m = 0.01hm

•kilo- 1000 1m = 0.001km

Prefixes Above Base

Prefixes Below Base

Selected Factors and FormulasConversion shown in bold are exact and should always be used for maximum precision

(~ means “approximately” and represents values accurate to the precision used)

Length

1 inch = 25.4 millimeters = 2.54 centimeters = .0254 meters (legal U.S.

definition)

1 millimeter = 1/25.4 inches ~ 0.04 inches (0.03937)

1 foot = 304.8 millimeters = .3048 meters (legal U.S. definition)

1 meter ~ 3.28 feet ~ 39.37 inches ~ 39 3/8 inches ~ 1.09 yards

1 mile = 5280 feet = 1609344 mm = 1609.344 meters = 1.609344 km

1 nautical mile ~ 1.15 statute miles ~ 6076 feet

1 rod = 16.5 feet



Area

1 township = 36 sq. miles ~ 6 miles X 6miles

1 acre = 43,560 sq. feet ~ 209 feet X 209 feet ~ .0016 sq. miles

1 sq. mile = 1 section = 640 acres

160 sq. rods = 1 acre



Volume

• 1 cubic foot ~ 7.481 gallons (U.S. liquid)

• 1 gallon ~ .134 cubic feet ~ 231 cubic inch ~ 3.785 liters (legal U.S.

definition)

• 1 liter ~ 0.264 gallon (1 gallon is about 4 liters)

• 1 cubic yard = 27 cubic feet = 46,656 cubic inches ~ 202 gallons

• 1 yard = 1 cubic yard

• 1 inch rain ~ 27,154.28 gallons/acre ~ 17,378,743 gallons/square mile ~ 10"

wet or 12" dry snow resulting in approximately 50% runoff, 20%

evaporation, 20% transpiration, 10% groundwater



Formulas

(A=area, L=length, W=width, C=Circumference, P=perimeter, R=radius,

D=diameter, H=height, S=surface, pi ~ 3.14159 (or 3.1416 for most

purposes), Y = short radius, Z = long radius)

Area

• Rectangle A = L * W P = 2L + 2W

• Parallelogram A = H * L

• Trapezoid A = H * (L1 + L2)/2

• Triangle A = (L + H)/2

• Circle A = pi x R2 C = pi x D

• Ellipse A = pi x Z x Y



Formulas

(A=area, L=length, W=width, C=Circumference, P=perimeter, R=radius,

D=diameter, H=height, S=surface, pi ~ 3.14159 (or 3.1416 for most

purposes), Y = short radius, Z = long radius)

Volume is the same for all regular shapes: V = A x H

Sphere V = (4/3) pi x R3

Cone V = (1/3) A x H

Pyramid V = (1/3) A x H

Scales (Drawing Units:World Units)

Scales Are Ratios Value on Left Represents Drawing (or Map)

Value on Right Represents Real World

1:1 One Unit on Drawing = One Unit in World

Drawing and Object Are the Same Size

1:2 One Unit on Drawing = Two Units in World

Drawing is One Half the Size of the Object

2:1 Two Units on Drawing = One Unit in World

Drawing is Two Times the Size of the Object

Scales in Different Disciplines

Design Disciplines That Use Metric Units Show Scales as Ratios

10000:1 500:1 5:1 2:1 1:1

1:10000 1:500 1:5 1:2 1:1

U.S. Mechanical Design Uses Ratios Also But Sometimes Include

8:1 4:1 1:4 1:8

U.S. Architectural Design Uses Ratios of Various Inches to 1 Foot

1/8”=1-0’ 1/4”=1.0’ 1”=1-0’ 3”=1-0’

U.S. Civil Design Uses Ratios of 1 Inch to Various Feet

1”=100’ 1”=1200’ 1”=5000’ 1”=10,000’

Orthographic Projection

Glass Box

Glass Box -- Unfolded

View Selection – First/Third Angle

Orthographic (Straight Line) Projection

View Selection – Front in True Shape

View Selection – Front Most Detail

View Selection – Horizontal Format

View Selection – Fewest Hidden

View Selection – Visually Stable

Alphabet of Lines

Line

Conventions

Alphabet of Lines

Thick Lines

Alphabet of Lines

Thin Lines

Alphabet of Lines Architectural and

Civil Engineering Can Use More

0.1mm thin lines in details, elevations, sections for

plotting clarity

0.2mm dimension, extension, center, hidden, leader,

phantom

0.3mm text, windows, doors, cabinets, stairs, railing,

ramps, existing

0.4mm object lines for mechanical parts

0.5mm object lines representing building elements in

architecture

0.6 mm elevation, profile, viewing/cutting plane lines

0.7 mm border lines

Hidden Lines

Section Lines

Section Lines

Conventional Break with dimension shown as "not to scale."

Section Lines

3

21

10

An assembly section showing the use of different symbols for iron, steel

and bronze. Solid fasteners are not sectioned when shown in length

(parts 6, 8, 9, and 10), only in an end view (part 1).

4

5

6

7

8

9

Section Lines - Assembly

Section

Lines

Sheet Sizes (1 IN = 25.4mm)

(~ means “approximately”)

Size ANSI Architectural Millimeters (~Inches)

U.S. ISO

A A4 11 X 8.5 12 X 9 297x210 (~11.7x8.3)

B A3 17 X 11 18 X 12 420x297 (~16.5x11.7)

C A2 22 X 17 24 X 18 594x420 (~23.4x16.5)

D A1 34 X 22 36 X 24 841x594 (~33.1x23.4)

E A0 44 X 34 48 X 36 1189x841(~46.8x33.1)

A, C, and E have same proportions

B, and D have the same proportions

Text Style and Height

Font – Drawings Use a Sans-Serif Font (Single Stroke Gothic)

ROMANS ARIAL CALIBRI

Case – Title Block Lettering Should be Upper Case

Sentences or Paragraphs of Text Should Be Sentence Case

Height – Generally Two Text Heights Are Used on Drawings

Large Text and Small Text at a 2:1 Ratio

Titles/Drawing Numbers .24” (.2” Sometimes) 6mm

Everything Else .12” (.1” Sometimes) 3mm

Title Blocks – A Size Mechanical

Title of Drawing in 6mm (.25”) letter height

Name of Company (Can Vary and Include Logo)

All other information

Date Name of CAD File Scale

Dwg No. Designer

Drafter Design Checker

Revision General Tolerances

Sheet Number Number of Sheets (3/6)

Material Method of Projection

Sheet Size ASME Standard Used

Document Stage Other Notes

Title Blocks – B Size Mechanical

Title Block in Lower Right Corner

Revisions Above or Left of Title Block

Bill of Materials Upper Right Corner

Architectural Title

Blocks

Can be Horizontal in

Bottom Right Corner Like

Mechanical

Can Be Vertical on Right

Side of Drawing Sheet

DimensioningASME Y14.5M-1994 ASME Y14.5M-2009

ASME Y14.5M-1994 and -2009

Dimensioning Practices

Geometric

Dimensioning and

Tolerancing (GD&T)

ASME Y14.41-2003

Deals with 3D digital models

Identifies exceptions to ASME Y14.5M

Model carries dimensional and tolerance

information

Reduces need for dimensions on drawings

Still need dimensions for QC and vendors

1.1 General

This standard identifies uniform practices

for engineering drawings

The standard doesn’t apply to:

Architectural Drawings

Civil Engineering Drawings

Welding Symbols on Drawings

AWS has it’s own standard for welding symbols

ANSI/AWS A2.4, Symbols for Welding and

Nondestructive Testing

1.1.3 Reference to Standards

When this reference is used, it should be

noted:

On drawing

In related documentation

The standard must be referenced as: ASME

Y14.5M-1994 or ASME Y14.5M-2009

Earlier Standards Still Sometimes in Use

1973 or 1982

Standard is Metric and Decimal Inch

•The U.S. officially adopted the metric system in

1866.

•U.S. customary units are defined by their metric

equivalents.

•The foot is legally defined to be exactly 0.3048

meter, making one inch exactly 25.4 millimeters.

•The pound is legally defined to equal exactly

453.59237 grams.

1.1.7 Symbols

Use symbols where appropriate

Use equivalent terms or abbreviations

where symbols are not appropriate

Symbols are preferred since they are

identical to the ISO standard

1.1.7 Symbols

1.3 Definitions - selected

Dimension -- a numerical value defining

Size

Location

Geometric Characteristic

Surface Texture

Basic Dimension – theoretically exact

Reference Dimension – for information only

1.4 Fundamental Rules

Dimensions shall clearly define intent

Each dimension must have a tolerance

Directly -- limit, bilateral or unilateral

Indirectly – general note or title block note

Decimal places can have tolerance significance

Exceptions:

Reference, Basic, Maximum, Minimum, Stock


Dimensions must be complete

Cannot be determined by measuring print

Cannot be assumed, except for:

90° angles

Loft, wiring, template, and master layouts on stable medium

Cannot be redundant

Reference dimensions should be limited


Dimensions must be clearly arranged

Dimensions must be subject to only one

interpretation

Manufacturing methods should not be part

of dimensioning unless essential to

engineering requirements

Hole Size, Location, and Surface Finish, but

not how to manufacture the hole


Dimensions should be arranged for

optimum readability

Dimensions should be placed in true

profile views

Dimensions should refer to visible outlines

Not Hidden Lines, if possible


Angles without dimensions are 90°

Dimensions apply at 20°C (68°F)

Dimensions apply in free-state condition

Dimensions and tolerances apply only at

the drawing level where they’re specified

Every feature must have a tolerance

Dimensions that locate it (specific or general)

Feature Control Frame

1.5 Units of Measurement

SI (Metric) linear units are millimeters

Customary U.S. linear units are decimal

inch, not fractions -- fractions are used

only as nominal sizes e.g. 1/2-20 UNC

Units are not placed on dimensions when

all are the same – note in title block

When mixed, add IN or mm as suffix to

exceptions

1.5 Units – Angles

Decimal

degrees or

Degrees

minutes and

seconds

1.6 Types – Metric

Metric dimensions have leading, but not following zeros

Except in bilateral or limit tolerances

1.6 Types – Decimal Inch

Decimal Inch

dimensions use

trailing, but not

leading, zeros

Same number

of decimal

places as

tolerance

1.7.1.1 Dimension Lines

Dimension lines have arrowheads

Preference for breaking line for numeral

If not broken, numeral goes above line

1.7.1 Not Dimension Lines

Do not use the

following as

dimension lines:

Center line

Extension line

Phantom line

Visible line

Dimension line can

be used as

extension line -- rare

1.7.1.1 Alignment – Important!

Chain dimensions

(where used) align

arrow-to-arrow

Group related

dimensions

together --

between views if

possible

1.7.1.2 Spacing Dimensions

Dimension spacing

First ≥10mm from

part

Subsequent ≥ 6mm

Modify for readability

if necessary

Extension line gap

~1.5mm (~.06IN)

1.7.1.2 Stagger Dimensions

Stagger

numerals for

parallel

dimensions

Place smallest

dimension

nearest part and

work out

1.7.2 Extension Line

Extension lines

extend a feature

Need a gap (1.5)

Normally 90° to

dimension line

Oblique OK

when needed

1.7.2 Crossing Extension Line

Avoid Crossing

Dimension Lines

Extension lines

Do not break

dimension lines

Break extension

lines only when

crossing arrow

1.7.3 Chain Lines

Use chain line to indicate limits for additional treatment

Dimension location if not obvious

Designate area with section lines and chain line (thick center linetype)

1.7.4 Leaders

A leader with

an arrowhead

points to an

edge

A leader with

a dot points to

a surface

1.7.4.1 Leader Directed Dims

Avoid complicated

single leaders

…but, also avoid

multiple leaders by

using times (X)

1.7.4.2 Circle and Arc

Leaders used to dimension circles or arcs must be radial (point towards or through the center)

Arrowheads never stop at center

1.7.5 Orientation – Notes (U.S. Only)

Notes must be

horizontal (parallel

to top of sheet)

ISO uses aligned

Dimensions with

lines and

arrowheads are

horizontal

1.7.5 Orientation – Baseline

Baseline

dimensions

are aligned

to their

dimension

lines from

bottom or

right

1.7.6 Reference Dimensions

Reference

dimensions

are placed in

parentheses

and used to

avoid over-

dimensioning

1.7.7 Overall Dimensions

If intermediate

dimensions

are more

important than

the overall, it

is a reference

dimension

1.7.9 Not-to-Scale – Hard Copy Original

Paper drawing dimension value changed

Geometry is not updated

Not-to-scale dimension is underlined

1.7.9 Not-to-Scale – Electronic Data

“Where the sole authority for the product

definition is a dataset prepared on a

computer graphics system, agreement

shall be maintained between the defining

dimension and the graphics presentations

of the feature in all views. The defining

dimension and the true size, location, and

direction of the feature shall always be in

complete agreement.”

1.8.1 Diameters

Use the

diameter or

spherical

diameter symbol

Concentric

cylinders can be

longitudinal –

often preferred

1.8.2 Radii

Use the radius,

spherical

radius or

controlled

radius symbol

Arrowhead

never goes to

center

1.8.2.1 Center of Radius

Use the same

size crosshair

for all centers

Show location

of radius by

dimensioning

the center

location

1.8.2.1 Radii controlled by tangencies

If center locations

aren’t

dimensioned, don’t

place a crosshair

Give enough

information to

locate tangent arcs

1.8.2.2 Forshortened radii

Arrowhead

part of

foreshortened

dimension

must be radial

Dimension

must be

foreshortened

1.8.3 Chords, Arcs and Angles

Chords are linear dimensions

Arc length dimension requires a symbol

Angle between radii uses arc dimension lines

1.8.4 Rounded Ends (not slots)

Fully rounded -

radius not

specified

Partially rounded -

radius specified

Rounded corner –

radius specified

1.8.7 Tangent Arc Outlines

Give all radius

values

Locate necessary

centers

Tangencies

determine others(some linear dimensions

not shown in example)

1.8.7 Irregular Outlines - coordinate

1.8.7 Irregular Outlines – tabulated

1.8.9 Round Holes

Use THRU only when unclear

Depth is depth @ full diameter

1.8.3 Slotted Holes Based on Method

Used to Manufacture

Radius (full)

indicated but

not specified

Method

depends on

how the slot

will be

manufactured.

Types of Holes

Counterbore (Blind) Counterdrill Countersink Spotface

1.8.11 Counterbored Holed

Use symbols for

counterbore and

depth

If remaining

material

significant,

dimension directly

1.8.11 Multiple Counterbore

Two

methods,

starting

with

smallest

hole

1.8.3 Countersunk and Counterdrilled

1.8.3 Spotface

Spotface uses the

same format as

counterbore, but

with no depth given

Depth is enough to

clean up or to

remove irregular or

cast surface

SF

2009

1994

1.8.15 Chamfers

1.8.3 Keyways and keyseats

Keyways from

opposite side of hole

Keyseats from

opposite side of shaft

Actual sizes calculated

or taken from tables

1.8.3 Keyways and keyseats

1.9.1 Rectangular Coordinate (baseline)

Tolerance Zones are Rectangles

1.9.2 Rectangular Coordinate Arrowless

1.9.3 Tabular Dimensioning

1.9.4 Polar Coordinate

Requires both a

radial linear

dimension and

an angular

dimension to

locate each

feature

1.9.4 Polar Coordinate

Tolerance zone

is keystoned

and changes

size with

distance from

center

1.9.5.1 Repetitive Features

Use the X Symbol

2.1 Dimensional Tolerances

Limit Tolerances

2.1 Dimensional Tolerances

Plus/Minus Tolerances

2.6 Accumulation of Tolerance Error

Chain Dimensioning


Baseline Dimensioning


Direct Dimensioning

2.7 Features of Size

Rule #1

2.12 Tolerance Linear/Angular

2.12 Basic Linear/Angular

2.7 Features of Size

2.14 Flat Tapers

2.14 Conical Tapers

2.14 Conical Tapers – Reference Dims

2.15.1 Radius not Controlled

2.15.1 Controlled Radius

Summary of Rules – Bad Practice

Summary of Rules – Better Practice

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