Sacramento City College EDT 300/ENGR 306 · Proportional Scales Proportional scales are used in drawing buildings and in making mechanical, electrical and other engineering drawings

EDT 300/ENGR 306 1

The Use of the ScaleThe Use of the Scale

Chapter 3Chapter 3

Sacramento City CollegeEDT 300/ENGR 306

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ScalesScales

Scales are used for laying off distances and for making measurements.

Scales are made in various shapes.Flat.Triangular shape.

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ScalesScales

Usually made of:Boxwood.Plastic.Plastic on boxwood.Metal.

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ScalesScales--Open or Fully DividedOpen or Fully Divided

Some scales are “open-divided” with only the end units subdivided.

Figure 3-33B and 3-33C.

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Some scales are “open-divided” with only the end units subdivided.

Figure 3-33B and 3-33C.

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Others are fully divided with subdivisions over their entire length.

Figure 3-33D and 3-33E.

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Others are fully divided with subdivisions over their entire length.

Figure 3-33D and 3-33E.

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Scale Types Scale Types

Different types of scales are used to make different kinds of drawings.

Architect’s scale.Mechanical Engineers scale.Civil engineers scale (decimal scale).Metric Scale.

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Scale Types Scale Types -- Architect Architect

Architect’s scale.Is used by architects primarily for producing drawings of buildings.Is graduated in fractions of an inch.Is divided into proportional feet and inches.

Typical architectural drawing scales:1/4” = 1’-0”1/8” = 1’-0”1-1/2” = 1’-0”3” = 1’-0”

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The ArchitectThe Architect’’s Scales Scale

The triangle shape is used most commonly.It has many scales on a single stick.Some drafters prefer flat scales especially when they do not have to change scales often.

Refer to Figure 3-33.

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The ArchitectThe Architect’’s Scales Scale

The triangle shape is used most commonly.It has many scales on a single stick.Some drafters prefer flat scales especially when they do not have to change scales often.

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Scale Types Scale Types -- Mechanical EngineersMechanical Engineers

Mechanical Engineer’s Scale.Has inches and fractions of an inch divided to represent inches.

DivisionsFull size - 1 inch divided into 32nds.Half size - 1/2 inch divided into 16ths.Quarter size - 1/4 inch divided into 8ths.Eighth size - 1/8 inch divided into 4ths.

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Scale Types Scale Types -- Mechanical EngineersMechanical Engineers

Mechanical Engineer’s Scale.Is used for drawing parts of machines.Is used for applications where largerreductions in scale are not needed.

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Scale Types Scale Types -- Civil EngineersCivil Engineers

Civil engineers scale (decimal scale).

1 inch can represent several quantitiesFeet.Rods.Miles.Etc.

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The Civil EngineerThe Civil Engineer’’s Scales Scale

Divisions are inches divided into decimals.The usual divisions are:

10 parts to the inch.20 parts to the inch.30 parts to the inch.40 parts to the inch.50 parts to the inch.60 parts to the inch.

The inch may represent different quantities such as feet, rods, miles, and so forth.

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In addition, the divisions may be single unitsor multiples of 10, 100 or 1000.

Example: 20 parts to an inch scale may represent

202002,000 units.

The scale is used for Civil Engineering workMaps and drawings of roads.Site plans.

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The scale used should be given on the drawing.

Scale: 1” = 500 feet.Scale: 1” = 100 feet.Scale: 1” = 200 miles.Scale: 1” = 100 miles.

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Proportional ScalesProportional Scales

Proportional scales are used in drawing buildings and in making mechanical, electrical and other engineering drawings.

The proportional scale to which the views are draw should be given on the drawing.

This usually is indicated in the title block if only one scale is used.

Common proportional scales:6” = 1’-0”3” = 1’-0”1-1/2” = 1’-0”

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Scale Types Scale Types -- Metric Metric

The proportional metric scale can be used on all types of engineering drawings when metric units are used.

Remember, the metric system allows easy conversion from one unit to another.

MetersDecametersHectometersKilometers

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The Metric ScaleThe Metric Scale

The Metric Scale is divided into millimeters.

Used for Architectural, Mechanical, Electrical drawings.

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Metric Proportional ScaleMetric Proportional Scale

Enlarged Same size Reduced2000:1100:1 1:1500:1 1:2100:1 1:1050:1 1:2020:1 1:5010:1 1:1005:1 1:500

1:10001:2000

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Dimension NotationDimension Notation

The symbol (’) is used for feet and (”) is used for inches.

Three feet four and one-half inches is written3’-4 1/2”.

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Indicating Drawing ScaleIndicating Drawing Scale

The scale of a drawing is ALWAYS indicated on the drawing.

If different parts of the drawing have different scales, the scales are given near the views.

If multiple scales are used they should be clearly indicated on the drawing.

EDT 300/ENGR 306 24

Using A ScaleUsing A Scale

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A drawing is created “to scale” under the following conditions:

When the object being drawn is too largefor the drawing sheet.

When the object being drawn is too smallto be read easily.

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When the object being drawn is too large for the drawing sheet.

Buildings.Property.Roads.Campuses.Airports.

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When the object being drawn is too small to be read easily.

Computer chip drawings.Small mechanical parts.Biomedical devices.

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FullFull--Size DrawingsSize Drawings

When the object being drawn will fit on the paper on which you are drawing it, draw it full-size or full-scale (1:1).\

ALWAYS try to draw full-scale FIRST !

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Drawings To ScaleDrawings To Scale

If you cannot draw full-scale, choose the largest scale that will fit on the sheet.

EDT 300/ENGR 306 30

Drawing With A ScaleDrawing With A Scale

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Drawing With A ScaleDrawing With A Scale--Full Size Full Size

If you draw an object FULL-SIZE, just transfer the dimensions directly.

1. Measure the distance of the object.

2. Align the “0” with one end of the object.

3. Read the length on the scale.

4. Draw a line representing that distance.

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Drawing With A ScaleDrawing With A Scale--Half SizeHalf Size

If you must draw the object HALF-SIZE and only had a FULL-SIZE scale, you would

1. Measure the distance of the object.


4. Convert the measured distance to half.

5. Draw the half distance on the paper.

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Drawing With A ScaleDrawing With A Scale--Full SizeFull Size

Drawing Full-Size with the Full Size scale:Measure the actual distance.Draw the actual distance.

Very easy !

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Drawing With A ScaleDrawing With A Scale--Full SizeFull Size

Drawing Half-Size with the Full Size scale:Measure the actual distance.Mentally divide the distance in half before drawing the distance on the sheet.

A real pain in the neck !

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Measuring With A Scale Half SizeMeasuring With A Scale Half Size

A Better Idea - Use a Half-Size ScaleLet the scale “do the work for you.”Think full-size, all the time. The scale would automatically convert for you.

Same example: with the half-size scale:Measure the actual distance directly.Draw the distance with the half-size scale using the same dimension directly on the scale.

(no mental math required)

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Think Think ““FULL SIZEFULL SIZE””

When using a scale, ALWAYS think FULL SIZELet the scale “do the work for you”.

The scale will automatically produce the proper reduction.

All you have to be concerned with is making accurate readings on the scale.

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Proportional Scale ChartProportional Scale Chart

Proportion Gradation RatioFull size 12” = 1’-0” 1:11/4 size 3” = 1’-0” 1:41/8 size 1-1/2” = 1’-0” 1:81/12 size 1” = 1’-0” 1:121/16 size 3/4” = 1’-0” 1:161/24 size 1/2” = 1’-0” 1:241/32 size 3/8” = 1’-0” 1:321/48 size 1/4” = 1’-0” 1:481/64 size 3/16” = 1’-0” 1:641/96 size 1/8” = 1’-0” 1:961/128 size 3/32” = 1’-0” 1:128

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Open Divided Architect ScaleOpen Divided Architect Scale

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EDT 300/ENGR 306 41

Making MeasurementsMaking Measurements

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Measuring With A ScaleMeasuring With A Scale

To make a measurement with a scale:

1. Place the scale on the paper in the direction in which you are measuring.


3. Read the exact length from the graduations on the scale.

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Sacramento City College EDT 300/ENGR 306 · Proportional Scales Proportional scales are used in drawing buildings and in making mechanical, electrical and other engineering drawings