Working Drawing Dimensions Sections

Lettering Instrumental Drawing Geometrical Construction Working Drawing Isometric Drawing

Working DrawingWorking Drawing


The concepts of points, lines and surfaces apply in orthographic projection.

The following holds true in orthographic drawings:

A point appears as a point in any plane of projections.

Lines perpendicular to the P.P. appears as a points.

Lines parallel to the P.P. appear as lines in their true size.

Theory of Orthographic Projections

Working Drawing


Lines inclined to the P.P. appear shorter.

Surfaces parallel to the P.P. appear in their true size and shape.

Surfaces perpendicular to the P.P. appear as a line.

Surfaces inclined to the P.P. appear not in true size and shape.



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1 2

3 4



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5 6

7



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Ct Dt

At Bt

Af Cf Bf Df As Bs Cs Ds

At Bt

Ct Dt

Cf Df

Af Bf As Bs

Cs Ds



Working Drawing


HE

IGH

T

HE

IGH

T

HE

IGH

T

DEPTH

DEPTH

WIDTH

WIDTH

WIDTH

DEPTH



HE

IGH

T

HE

IGH

T

DE

PT

H

DEPTHWIDTH

WIDTH

FRONT VIEW SIDE VIEW

TOP VIEW



AUXILIARY VIEW




TOP VIEW

REFERENCE LINE PARALLEL TO THE ENCLINED SURFACE

DIRECTION OF SIGHT PERPENDICULAR TO THE INCLINE SURFACE

PART AUXILIA

RY VIEW




TOP VIEW

THREE PRINCIPAL VIEWS

Working Drawing

Multiview Projection


HE

IGH

T

WIDTH DEPTH WIDTH DEPTH

WIDTH

WIDTH

DE

PT

H

TOP VIEW

BOTTOM VIEW

REAR VIEW L-SIDE VIEW FRONT VIEW R-SIDE VIEW

HE

IGH

T

HE

IGH

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DE

PT

HSIX REGULAR VIEWSSIX REGULAR VIEWS

Working Drawing

Multiview ProjectionMultiview Projection


HORIZONTAL PLANEHORIZONTAL PLANE

LINE OF SIGHT PERPENDICULAR TO PLANE


TOP VIEWTOP VIEW



FRONT VIEWFRONT VIEWLINE OF SIGHT PERPENDICULAR TO PLANE


FRONTAL PLANEFRONTAL PLANE



LINE OF SIGHT PERPENDICULAR TO

PLANE

LINE OF SIGHT PERPENDICULAR TO

PLANE

PROFILE PLANEPROFILE PLANE

SIDE VIEWSIDE VIEW



THE GLASS BOXTHE GLASS BOX



width

he

igh

t

UNFOLDING THE GLASS BOXUNFOLDING THE GLASS BOX



Visible line – used to show the outlines and corners that can be seen when the object is viewed.

Hidden line – used to show edges and corners that are not normally seen when the object is viewed.

Section line – used to show cut surfaces of the object in sections.

Center line – used to indicate the center of a circle or arc, or to indicate the axis of objects with circular features. In some cases the center line is also used as an extension line.

Alphabets of LinesWorking Drawing


Dimension and Extension lines – used to indicate the direction and the extent or size of a part in a drawing and to show the relative position or location of the features. Dimension lines are terminated by arrowheads at the extremities. Its three parts are the fine line, arrowheads and numerical value.

Cutting plane line – this is used to indicate which part of the object is imaginarily cut in sections.

Short break line – this is used to show the edge of the object from which a part has been cut. This line is drawn freehand and applicable if the object is not large.

Alphabets of LinesAlphabets of LinesWorking Drawing


Long break line – this has similar use as short break line. It is used to show that the object has been cut in a certain part usually in half—sectional views. It is used to reduce the size of the view.

Leader line – sometimes called the porter, is a thin solid inclined line, leading from a note or dimension terminated by an arrowhead towards the part indicated. They are drawn at an angle to connect with the principal line. In arcs and circles, leaders are along radial lines.

Alphabets of LinesAlphabets of LinesWorking Drawing


Phamtom line

Used to show the position of moving parts

+ +Visible line (thick)Visible line (thick)

Hidden line (thin)Hidden line (thin)

Working DrawingApplication of the Alphabets of Lines


Section line (thin)Section line (thin)

+ +

Center line (thin)Center line (thin)

Working DrawingApplication of the Alphabets of LinesApplication of the

Alphabets of Lines


Dimension & extension lines (thin)Dimension & extension lines (thin)

60

Extension lineExtension lineDimension lineDimension line

75

Cutting plane line (thick)

Cutting plane line (thick)


Alphabets of Lines


Short Break line (thick)

Short Break line (thick)

Long Break line (thin)

Long Break line (thin)


Alphabets of Lines


15 DIA. In 2 Holes15 DIA. In 2 Holes

10 R. In 4 Corners10 R. In 4 Corners

Leader line (thin)Leader line (thin)

Phamtom line (thin)Phamtom line (thin)


Alphabets of Lines


Dimensions, extension and leader lines are drawn in light solid lines.

Extension lineExtension lineLeader lineLeader line

Dimension lineDimension line

50

Rules In DimensioningWorking Drawing


Extension lines must begin about 1 mm. from the object and should extend about 2 mm. beyond the dimension line.

2 m

m. 1 m

m.

50

Rules In DimensioningRules In DimensioningWorking Drawing


Dimension lines must be kept at least 10 mm. away from the object lines and 10 mm. away from each other.

25 25

50

10 m

m.

10 m

m.

10 m

m.

10 m

m.



The smaller or detail dimensions should be nearest to the view and the overall dimensions should be farthest away.

Detail dimensions should be kept in one line.

detail dimensions

detail dimensions

30 20 40 20

110Overall dimensionsOverall dimensions



20

40

20

45

22.5 22.5

20

20

Unnecessary repetition of dimensionsUnnecessary repetition of dimensions

Dimensions are not to be repeated.



Keep dimensions between views if possible.

Dimensions should not be placed upon a view unless necessary.

2015

35

15 15 15

45

20

Top view

Front view

Side view

Top view

Front view

Side view



Center lines are used as extension lines in dimensioning distances of circles.

15 30 30 15

1515



For dimensioning limited space, arrowheads should be reversed.

5 50 5



Hidden lines should not be dimensioned unless necessary.

20



Circles are dimensioned by giving the diameter.

300

Dia. 20



Arcs are dimensioned by giving the radius.

R20

R15



Angles are dimensioned by means of arcs and arrowheads.

30 o

45o



INTRODUCTION

Orthographic projections can show both the internal and external features of an object.

The customary use of dashed lines to show the internal features of an object can sometimes be confusing.

The excessive use of hidden lines make drawing difficult to read and understand.

To clearly describe the object several views are drawn showing the object as if a portion had been cut to reveal the interior.

This convention is called sectioning. Sectional views can be represented in both orthographic and isometric drawing.

Sectional ViewsWorking Drawing


Isometric viewIsometric view

Isometric sectionIsometric section

Orthographic sectionOrthographic section

Sectional ViewsSectional ViewsWorking Drawing


Sectional views are used to clarify interior or hidden details on a multi—view drawing of an object.

A sectional view usually replaces of the principal views (top, front and side) but may also be an additional view or a series of supplemental views depending on the type.

Section views are located by creating a Cutting Plane Line in one view.

The Cutting Plane Line is a thick, dark line composed of a long dash, two short dashes and a long dash.



Cutting plane line

Section Lining or Cross Hatching is added to the Section view to distinguish the solid portions from the hollow areas of an object and can also be used to indicate the type of material that was used to make the object.



Some of the material symbols used for section lining.

Gen. purpose or cast ironGen. purpose or cast iron

SteelSteel

Magnesium or aluminumMagnesium or aluminum

Bronze, brass or copperBronze, brass or copper

White metal, zinc, leadWhite metal, zinc, lead



Full Sections

Is constructed by passing an imaginary cutting—plane completely through the object.

The arrows indicate the direction of sight, and all the hidden features intersected by the cutting—plane are represented by visible line in the section view.

Top viewTop view Section viewSection view

Front viewFront view Side viewSide view

Types of SectionsSectional Views


Half Sections

Are created by passing a cutting—plane only halfway through the object.

The figure shows a half section view with a quarter of the object removed.

Note that, hidden line are omitted from the section view, but maybe added to the unsectioned half for clarity.

The external features of the object are drawn on the unsectioned half of the view, and a center line is used to separate the two halves.

This is drawn in objects which are symmetrical.

Types of SectionsTypes of SectionsSectional Views


Half Sections



Offset Sections

An offset section is constructed with a non—linear cutting plane line.

The cutting plane line is bent at 90 degrees in order to pass through the important features of the object.

Once the section is established, the corners of the cutting—plane line are not shown on the section view.

Multiple cutting—plane lines can be used on one object if needed.



Offset Sections



Removed Sections

Removed sections are made in a manner similar to revolved sections, except the cross section is being drawn adjacent to the orthographic view, and not on it.

Removed sections are used when there is enough space on the orthographic view for a revolved section.

Removed sections are used to show the contours of complicated shaped and other parts that have continuously varying shaped.

Normally, the cross—section view is drawn adjacent to the orthographic view and close to the position of the cutting—plane, which is identified either with a center line or a cutting plane—line.



Removed Sections



Broken—out Sections

A broken—out section is used only a small portion of the object is removed and sectioned.

A broken—out section is used instead of a Full or Half Section to provide only the needed detail, and also to save time.

A free hand break line separates the sectioned portion from the unsectioned view.

A cutting—plane is not used since the removed section is chosen at random.



Revolved sections

A Revolved Section is constructed by revolving a crow—sectioned view 90 degrees about an axis of revolution.

The section view is then superimposed between conventional break lines on the orthographic view. The new cross—section is drawn true size and shapes to fit the view.



Revolved sections


Working Drawing Dimensions Sections

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