6 cross section view(1) 2

SECTION VIEWS

ContentsIntroductionBasic componentsKind of sectionsDimensioning

UNDERSTANDING SECTIONSSectional views, commonly called sections, are used to show interior detail that is too complicated to be shown clearly and dimensioned by the traditional orthographic views and hidden lines.

A sectional view is obtained making an imaginary cut through the part, and by drawing the features on the cut surface, as shown below:

ExampleRegularviewSectionview

To aid in visualizing the internal workings of a design like :- Clarify an internal feature- Facilitate dimensioning

GivenNecessity of a section viewFinishNoInternal featuresmake a viewdifficult to reador dimension?Orthographic projectionprincipleYesSectiontechniqueOrthographic projectionprinciple

ExampleRegularviewSectionview

Section Basic componentsCutting PlaneCutting Plane Line CPLSection Lines

Cutting plane is an imaginary plane that cuts through the object.Location and direction of a cutting plane depend on a hidden feature that is needed to be revealed.A section view is obtained by viewing the object after removed the cover up part in the direction normal to the cutting plane.CuttingplaneExampleSection viewBasic ComponentsThe Cutting Plane

Visible Edges on Cutting PlanesNewly visible edges cut by cutting plane are crosshatched with section lining.

LABELING CUTTING PLANESNote that each section (A-A and B-B) is completely independent.

*Technical Drawing with Engineering Graphics, 14/eGiesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved.

Visualizing Cutting-Plane DirectionCorrect and Incorrect Cutting-Plane Line Placement

Cutting plane lineIn an orthographic view, a cutting plane is presented as a cutting plane line, CPL and is drawn in either of an adjacent view of the section view.GivenDirection 1Direction 2Direction 3SectionviewCPLCPLSectionviewSectionview


CUTTING-PLANE LINE STYLEIt is made up of equal dashes, each about 6 mm (1/4) long ending in arrowheads. This form works especially well for drawings. The alternative style, uses alternating long dashes and pairs of short dashes and ends with arrowheads. This style has been in general use for a long time, so you may still see it on drawings. Both lines are drawn the same thickness as visible lines. The arrowheads at the ends of the cutting plane line indicate the direction in which the cutaway object is viewed.Alternative Methods for Showing a Cutting PlaneA and B.

ViewingdirectionCutting plane line : Line stylesThe cutting plane line is presented by a chain line. (This course)Begin and end the line with a short visible line.When the line changes its direction, draw a short visible line at that corner.Draw an arrow at about the mid-length of a short visible line, the arrow head is pointed toward to this line in a viewing direction.Examples123Basic Components

Class activityDo you find something wrong in the following cutting plane lines?YesNoRight!Wrong!(The arrow on the right side should be pointed downward)YesNoRight!Wrong!(The arrow head have to touch the short visible line)YesNoRight!Wrong!(Because the cutting plane line used in this course is a chain line )

Section lining : PurposeSection lines or cross-hatch lines are added to a section view to indicate surface that are cut by a cutting plane.ExamplesSection viewwithout section linesSection viewwith section linesVisible surfaces and edges behind the cutting plane are drawn in a section view.

The section lines are different for each type of material.Cast iron,Malleable ironSteelConcreteSandWoodPractically, the cast iron symbol is used most often for any materials. Section lining : SymbolExamples

Section-Lining SymbolsSection-lining symbols may be used to indicate specific materials.These symbols represent general material types only, such as cast iron, brass, and steel.Symbols for Section Lining

SECTION-LINING TECHNIQUE Uniformly spaced by an interval of about 2.5 mm

Not too close together

Uniformly thin, not varying in thickness

Distinctly thinner than visible lines

Neither running beyond nor stopping short of visible outlines

SECTION-LINING TECHNIQUE continued.

Section-Lining in CADCAD programs usually include libraries that allow you to select from a variety of section-lining patterns, making it easy to use different patterns, angles, and scales for the spacing of the pattern.


RULES FOR LINES IN SECTIONVIEWS Show edges and contours that are now visible behind the cutting plane.

Omit hidden lines in section views.

A sectioned area is always completely bounded by a visible outlinenever by a hidden line.

A visible line can never cross a sectioned area in a view of a single part.


Kinds of sectionFull sectionOffset sectionHalf sectionBroken-out sectionRevolved section (aligned section)Removed section (detailed section)

Conventional practice : Treatment of a hidden lineHidden lines are usually omitted within the section lined area.ExampleHidden linesare omitted.Hidden linespresent.

Full Section View: Concept & exampleA section view is made by passing the straight cutting plane completely through the part.Example

A closer lookKinds of sections

Offset section : Concept & exampleA section view is made by passing the bended cutting plane completely through the part.ExampleEdge views ofthe cutting planeare omittedKinds of sections

Half section : Concept & exampleA section view is made by passing the cutting plane halfway through an object and remove a quarter of it.Example

Half sectionCutting plane

A section view is made by passing the cutting plane normal to the viewing direction and removing the portion of an object in front of it.Broken-out section : Concept & exampleExampleKinds of sections

Revolved section : Concept & exampleA section view is made by revolving the cross-section view 90o about a cutting plane line and drawn on the orthographic view.Example

1. Superimposed to orthographic view.SuperimposedBreak2. Break from orthographic view.Revolved section : Placement of a cross-section view

Revolved section : Additional exampleKinds of sections

6. Removed sectionRemoved section is created with the same concept as a revolved section. But, the cross-section view is shown outside the view.Removed sectionComparison with a revolved sectionRevolved sectionRemoved section

Example : Situation that removed section is preferred.Removed section : AdvantageRemoved section technique can improve a reading of the orthographic view.ExampleRevolvedsectionRemovedsection

Section AA Section BB A single or multiple removed (cross) section view(s) can be arranged without aligning with the cutting plane line, but it have to be labeled name of the cutting plane line.Removed section : Alternative placement of a viewExampleKinds of sections

SummaryDrafter has several choices of section techniques to reveal an internal feature of an object.Object having a symmetry, an appropriate choice is such as full section or half section.Object having several features that do not locate in-line among each other, an offset section may be a good choice.Broken-out section is usually used when a drafter need to reveal a local detail of each feature.Revolved and removed section views are efficient when a drafter need to reveal only a cross section shape of an object.Kinds of sections


ASSEMBLY SECTIONSSection views are often used to create assembly drawings.Notice that the hatching on different parts has different hatch patterns or hatch at different angles. When used on the same part, the hatching is always at the same angle to help you recognize the parts easily.

Comparison of a different section techniques


CONVENTIONAL BREAKSAND SECTIONSConventional breaks are used to shorten the view of an object that is too long to show clearly at one scale on the drawing sheet.

Rib and Web are thin, flat feature of an object that acts as a structural support.Thin features in section views

RIBS IN SECTIONTo avoid giving a false impression of thickness and solidity, ribs, webs, gear teeth, and other similar flat features are not hatched with section lining even though the cutting plane slices them.Thin features are not hatched if the cutting plane passes lengthwise through them.

Spoke is the rod radiating from the hub to the rim of a wheel.SpokeRimHub

Lug is an ear which is built as portion of an object for attachment.

ExampleLugRib

ExampleStandard mechanical parts like shafts, bolts, nuts,.. are not sectioned


ALIGNED SECTIONSWhen parts with angled elements are sectioned, the cutting plane may be bent to pass through those features. The plane and features are then imagined to be revolved into the original plane.Aligned SectionThe angle of revolution should always be less than 90 for an aligned section.



Example

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6 cross section view(1) 2

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