section views

Lect 13 P. 1

Engineering H191 - Drafting / CAD

Autumn Quarter Gateway Engineering Education Coalition

Section Views

Lecture 13

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Topics For Today

• Sections Views– Why section views are needed– Types of section views– References• BTG Chapter 6

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Section Views

• Goals– Recognize various kinds of section views,

make full and half section views.– Improve visualization of interior features.

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Section views are used when important hidden details are in the interior of an object. These details appear as hidden lines in one of the orthographic principal views; therefore, their shapes are not very well described by pure orthographic projection.

Section Views

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Types Of Section Views

• Full sections• Half sections• Offset sections• Revolved sections• Removed sections• Broken-out sections

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Cutting Plane• Section views show how an object would look if a

cutting plane (or saw) cut through the object and the material in front of the cutting plane was discarded

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Section Lines

• Section lines (crosshatching) are used to show where the cutting plane passed through solid material

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Full Section View

• In a full section view, the cutting plane cuts across the entire object

• Note that hidden lines become visible in a section view

Hidden Lines are Visible

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Full Section View

•Shows cutting plane in the top view•Makes a full section on the front view

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Full Section View

•Note how the cutting plane is drawn and how the crosshatching lines mark the surfaces of material cut by the cutting plane. •No hidden lines on the section view, if possible.•Note: Interior lines behind cutting plane became visible.

Visible lines omitted

Incorrect

Correct

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Multiple Sectioned Views

SECTION A-A

AA

SECTION B-B

B

B

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Half Section View

The cutting planes do not cut all the way through to the object. They cut only half way. They intersect at the centerline.

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• Half Section used mainly for symmetric objects

Half Section View

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Revolved Sections

• Revolved sections examples show the shape of an object’s cross-section superimposed on a longitudinal view

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Removed Sections

Removed sections are like revolved sections but moved aside. Note how they are named.

A

A

Section A-A

C CSection C-C

B

B

Section B-B

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Broken Out Sections

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Offset Sections

Offset sections are used to show interior features that do not lie along a straight line

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Offset Sections

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Conventional Revolutions

• Used to make section views clear and avoid confusion

• Associated with objects that have holes, ribs, spokes, or lugs in any combination equally spaced in a circular fashion

• Not projected orthographically to section view• Examples to follow

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Conventional Hole Revolutions

• Note no hidden lines

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Conventional Rib Revolutions

• Note: Ribs not crosshatched

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Conventional Spoke Revolution• Note: Spokes not crosshatched

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Holes and Ribs in Combination

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Assignment

• Dwg 25 – F18-A – Complete section views– Due at end of today’s lecture

• Dwg 26 – SECT 1-N– Sketch Section Views– Due at beginning of next lecture

section views

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