1. Question of the Day What is the origin of the phrase
“The Whole Nine Yards”?
ANSWER:
Meaning to give absolute maximum effort when trying to win or achieve something
From the 2nd World War; the American B-17 aircraft guns used ammunition belts that were nine yards long
… When the gunners let lose on something, they gave it the “whole nine yards” of ammunition
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2. Topics For Today Sections Views Why section views are needed
Types of section views
References
BTG Chapter 6
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3. Section Views
Goals
Recognize various kinds of section views, make full and half section views.
Improve visualization of interior features.
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4. Section Views
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.
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5. Types Of Section Views Full sections Half sections Offset sections
Revolved sections
Removed sections
Broken-out sections
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6. 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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7. Section Lines
Section lines (crosshatching) are used to show where the cutting plane passed through solid material
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8. Hidden Lines are Visible
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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9. Full Section View Shows cutting plane in the top view
Makes a full section on the front view
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10. Full Section View
Visible lines omitted
Incorrect
Correct
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.
Note that the last bullet is intended to highlight that what may have been hidden lines before the cutting plane may now be visible lines.
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11. Multiple Sectioned Views
SECTION A-A A
SECTION B-B B
Multiple section views can be created on a single multiview drawing. This example shows a horizontal and profile section view. Note that each section view is labeled to correspond to its cutting plane line.
Also note that in other examples we have almost always put the cutting line on the top view and shown the sectioned view as the front view. The homework problems at the end of the chapter are of the type shown by AA in this diagram. Cutting plane line on front view, therefore cutting plane shown on the top view. Good place to reinforce the meaning of the direction of the arrows on the cutting plane line.
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12. 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.
May be good to note to the students that a full section view removes ½ the object. A half-section view only really removes ¼ of the object.
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13. Half Section View Half Section used mainly for symmetric objects
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14. Revolved Sections
Revolved sections examples show the shape of an object’s cross-section superimposed on a longitudinal view
Might be confusing to students. Note that these are four separate examples.
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15. Removed Sections A
Section A-A C
Section C-C B
Section B-B
Removed sections are like revolved sections but moved aside. Note how they are named.
In removed sections, the section view consist only of the sections removed at the cutting plane and not the entire sectioned part. Thus, the section views are views of thin slices of the cross section along the cutting plane. The students need to understand this convention in removed sections.
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16. Broken Out Sections
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17. Offset Sections
Offset sections are used to show interior features that do not lie along a straight line
Note that the section line is staggered and has edges in the top view but these edges are not represented in the front view as lines according to the convention.
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18. Offset Sections Lecture 13 - Cadkey
Note that the section line is staggered and has edges in the top view but these edges are not represented in the front view as lines according to the convention.
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19. 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
Using Croft, Meyers, et al as reference pages
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20. Conventional Hole Revolutions
Note no hidden lines
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21. Conventional Rib Revolutions
Note: Ribs not crosshatched
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22. Conventional Spoke Revolution
Note: Spokes not crosshatched
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23. Holes and Ribs in Combination
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24. Assignment Dwg 25 – F18-A Dwg 26 – SECT 1-N Complete section views
Due at end of today’s lecture
Dwg 26 – SECT 1-N
Sketch Section Views
Due at beginning of next lecture
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