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SCALES

Done as Ratios or Equivalent Units Reading a Scaled Drawing Creating a Scaled Drawing

 

Scale as a RATIO

Often the scale of the drawing is just specified as a ratio of the size

of the Drawing Units to the of the Object’s actual length or D:O Alternate terminology is Paper:Real or Print:Real Consider it as a fraction…. helps you visualize if the drawing is

going to be larger or smaller than the actual object. Is D/O larger than 1? Then drawing on paper is larger than object’s real size. If D/O is smaller than 1, then the drawing on the paper is smaller than the object’s real size.

See Fig 11 page 31

SCALE 1:1FULL SIZE

SCALE 1:2

1/2 Also known as HALF SIZE

2

SCALE 2:1

2/1 Also known as

DOUBLE SIZE

REAL

REAL

 

 

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Difference between MECHANICAL and ARCHITECTURAL

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Watch for the SIZE label and the number of divisions. SIZE refers to MECHANICAL: “n” inch = 1 INCH Where “n” can be 1/4, 3/8, 1/2, or 3/4 of an inch Divisions of 2, 4, 8, 16, 32 for fraction of an inch measurement

1/4 INCH = 1 INCH

G

G is 6 5/8 inches

In this case “n” is ¼, there is a Size label so it is Mechanical There are 8 divisions, so each division is represents 1/8 inch

in real space.

Inches on both sides of equation!

See Fig. 17 on pg. 35

MECHANICAL

 

Difference between MECHANICAL and ARCHITECTURAL

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No “SIZE” label refers to Architectural: “n” inch = 1 FOOT 12 divisions (or 6, 24, or 48) on end for

inch and fraction of an inch measurements

1/4 INCH = 1 FOOT

W ARCHITECTURALW is 4 FT. 8 IN. You don’t call it 4 8/12 FT.

NO SIZE LABEL

In this case “n” is ¼, there is NOT a Size label: Architectural There are 12 divisions, so each division represents

1 inch in real space. Since there are 12 inches per foot.

See Step by Step on pg.37

NOT SAME UNITS ON BOTH SIDES

 

Slide 5 

 

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ENGINEERS SCALE5

Has 10, 20, 30, 40, 50, or 60 divisions per inch. Each different scale can be used for ANY power of ten. 50 scale could be used for:

1” = 50 feet or 1” = 5 feet or 1” = 0.05 feet Actual equivalent UNIT can also vary! 50 scale could be used for:

1” = 50 MILES or 1” = 500 microns

1 inch

F 710 MICRONS

FOR 1 INCH = 500 MICRONS

F is

See Sec. 8 on page 35

EXAMPLE OF ENGINEERS SCALE6

FOR 1 INCH = 3 FEET A is 5.3 FEET

FOR 1 INCH = 30 FATHOMS A is 53 FATHOMS

A30 divisions per 1 inch.

1 inch 20 divisions per 1 inch.

1 inch 10 divisions per 1 inch. (you have this one)

FOR 1 INCH = 200 FEET A is 360 FEET

 

 

 

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Decimal Inch Scale• Has each inch divided into 50 divisions (1/50th of an

inch) or decimal of .02 for each mark.• Can only be used for FULL SIZE drawing.

Z1 inch

1.68 inches

SCALE 1” = 5 FT.K would be

1 inchK

5 FT

Different from 50 Scale

Z would be

7.5 FEET

7 See Sec 9, Fig. 16 on pg. 35 

Reading a drawing DONE TO SPECIFIC SCALE Determine which scale to use.

Architectural? Mechanical? Engineers? Determine its smallest increment.

inches, 1/8th inch, .01 meters, etc. Does your answer make sense?

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Line up “whole” unit, then read the partial leftover on end.

Actual size would be 3 FEET 1 I/2 INCHES

Cross Section Drawn at SCALE ½ IN.= I FT.

 

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- AND ANOTHER EXAMPLE -

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SCALE 1 INCH = 1 FOOT

Want answer in fractions of an inch.

The 3, 6, 9 refer to inches.Smallest increment is 1/4 of an inch.

Actual length read is 1 FT. 5 3/4 IN.

 

- AND ANOTHER EXAMPLE -10

SCALE 1 INCH = 10 μm

Actual Height read is 7 μm

 

 

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CREATING A SCALED DRAWING11

Need to know or determine actual size. Need to know or decide on SCALE to be drawn at.

Depends on paper size used. See Fig. 37 on page 48A= 8.5” x 11.0” C= 17.0” x 22” E = 34.0” x 44.0”B= 11.0” x 17” D= 22.0” x 34”

For example, given the specs: Actual length of pipe is 4 - 21/32” Draw the pipe at a SCALE 3”= 4”

This could be considered also as 3/4” = 1” Inch to INCH (NOT Inch to Foot) means Mechanical,

need the one with Size label.

Start at 4

smallest increment here is 1/32nd inch

 

 

Scale can be used to create RATIO drawings.

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* Just look at pictures shown here, do not lay your scale on these, the handout has been scaled!

Redraw using the regular rule (nearest 1/16th of an inch)

Create drawing of clip SCALE 4:1

Measure the size using the Scale in reverse.

In this case, measuring the clip using the 1/4 SIZE Scale results in a size of

*7 7/8 inches

 

 

DRAW 

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SCALES and CAD Create elements as

“REAL” size ie make it “FULL SIZE”

PLOT at different scales EASILY without having to redraw the elements. Let the program do the

work. Engineering Graphics

usually DO NOT print to fit.

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Do not use Fit to Paper

We’ve been using 1:1 but there are other options.

See CAD at Work on pg. 52

 

 

   

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SCALES Lecture: WORKSHEET