Reading Drawings Copyright © Texas Education Agency, 2012. All rights reserved. 1.

Reading Drawings

Copyright © Texas Education Agency, 2012. All rights reserved.

1

Why Have a Plan or Blueprint?

• There are different types of plans or blueprints to allow the viewer different visual clues for producing the products.

• Drawings are used to make the parts.• The drawing standards have been set for ease

of understanding and producing the part.• There are different types of lines used to draw

a blueprint or a plan.


2

Machined Toy Top

1 dia.

2.75

1.50 .75

.25 dia.


3

Types of Drawings


4

Three View Drawing or Working Drawing

The three view drawing or working drawing shows the object from three sides. These views will show the shape of the object and location of any cutouts or holes.The dimensions are usually added to this type of plan.

1

1 1/2

3

2 1/2

1 3/4


5

Oblique Drawing

The oblique drawing is a pictorial drawing showing the shape of the object.The drawing is drawn as a front view, then the depth is projected from the corners at an

angle.There are no dimensions or hidden lines on an oblique drawing.


6

Isometric Drawing

The isometric drawing is drawn at a 30degree angle for the front and the side.This gives a 3D effect to the drawing.There are no dimensions or hidden lines on an isometric drawing.


7

Exploded View Drawing

This drawing shows how parts in an assembly fit together.


8

Sectional View Drawing

The sectional view is a drawing with a part removed or cut out to show the internal parts of the part.


9

Sheet Metal Development Drawing

This drawing shows a box or other sheet metal project in a flat view. It allows the project to be laid out on metal, cut and folded in the finished product.


10

Welding Plans

.

The welding drawings describe how the weld joints are to be produced.


11

Drawing a Plan


12

Drawing a Plan

• Only necessary views are drawn.• They show shape, location and size.• The front view shows the most detail.• Dimensions are in between views if possible.• Other views may be added for clarification.


13

Drawing Projection


14

Fig. 256 Revolution of the Planes of Projections.Fig. 257 All Planes Are Revolved until they Coincide with the Front Plane

Six Views of an Object

Copyright © Texas Education Agency, 2012. All rights reserved. 15

Necessary Views of a Drawing

The three views in black are the necessary views: front, top, and right side.The three views in red are mirror images of the black views and show the details as hidden lines.


16

Dimensions on a Drawing

3

2

1 ½

1

1

1 ½

1

1

1

2

1

1 ½ 1 ½

3

Dimensioning each view makes the drawing too difficult to understand. The dimensions are placed on the drawing only once.


17

Correct Placement of Dimensions

1

1

2

1 ½

3


18

Types of Lines on a Blueprint

What do dashed

lines mean? What are all the

arrows pointing to?


19

Line Symbol Definition

Object Solid black line showing the shape of an object

Hidden Dashed line as dark as the object line shows shapes covered by other parts. For example, depth of a hole, etc.

Center Line with a dash in the middle or a plus with lines radiating from it shows where the center is located.

Section Line that has long and short sections with arrows pointed out shows the inside of a part by cutting out a section.

Fold Line with 2 X’s show where to fold a sheet metal development.

Extension A thin line extending from the edge to the dimension line indicates the dimension.

Dimension Thin lines pointing to the extension lines show the measurement.

+

X X

2


20

Plan Dimensions

• Measurements are in inches or mm.• Dimensions have three parts: extension lines, arrows and the number.

• The largest measurements are on the outside of the set of dimensions.

6 1/4

Extension linesDimension number

Dimension arrows


21

Examples of Plans


22

Fig. 304. Draw views with instruments; add missing lines. Layout 3D (Appendix I).

Worm Saddle Plans

2 1/2 2 1/2

2 7/8

7 1/2

1 1/2

3/4

1/4

3

2 Dia.

7/8 2 7/8

½ DRILL 2 HOLES

7/8 DRILL

3

WORM SADDLE


23

Reading a Basic Drawing

1 1/2

1/2

2 1/24

1/2 DRILL4 HOLES

1 R

3/4 R

1/2 12

1. What is the total length of the part?

2. What is the total height of the part?

3. Explain the dashed lines on the drawing?


24

Hammer Drawings

1/2” ROUND

31/4-20 THREADS 3/4” DEEP

HAMMER HANDLE

61/4” ROUND 1/4-20 THREADS x ¾ LENGTH BOTH ENDS

HAMMER SHANK

3/4 SQUARE

2 1/2

1 1/8

3/8

3/8

1/4-20 THREADS 3/4” DEEP

HAMMER HEAD


25

Exploded View of Hammer

The exploded view shows how to assemble the hammer.


26

Sheet Metal Development

Prism Cylinder

PyramidCone


Fig. 568 Development of Surfaces

27

Sheet Metal Layout Drawings

• The layout is a flat drawing with cut and fold lines drawn.

• These lines are used to form (develop) the 3D shape.

• Drawings have tabs, folds, and hems shown.


28

Sheet Metal Box Plans

8 1/2 5

1/4 Hems All Around

11

8 1/2

1

1

45°

XXX

XXX

XX

X

XX

X

X

X

X

X

X X

XX

Hem

Fold

Hems fold over the edges so it is not sharp and the edge is strengthened.Folds are marked to allow for bending the shape.


29

Sheet Metal Layout Plans

2

3

2

2

5


30

Sheet Metal Layout Plans Or Development

10 1/2

2 2

2

1

1

ALL HEMS 1/4”

13

1

1

3 7 1/2

X

XXX

XX

XXX

XX

XX

XX

X

XX X

X

XX

XXX

X

XX

XXX

X

X

X

X

X


31

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