TA 101

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Anupam Saxena

Associate Professor Mechanical Engineering Compliant and Robotic Systems Lab Indian Institute of Technology Kanpur

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for the drawing

Comes with practice… and with MISTAKES !

PULLEY 1 NOS  24  40  80 50 30 10 5

ANUPAM SAXENA TA101 LECTURE XII SECTIONAL AND ASSEMBLY VIEWS

BRACKETS 2 NOS  20 2 x  10  15 R15 50 80 10 10 20  40 15

ANUPAM SAXENA TA101 LECTURE XII SECTIONAL AND ASSEMBLY VIEWS

170

TA 101

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What does GOD (google) say about sectional views?

In section view drawings, hidden line representation is omitted in that part of the view with the section lining.

A correct conventional representation of the full section in the front view omits these hidden lines . In all cases the top view of the drawing is a standard orthographic view complete with visible and hidden lines .

Visible object lines centerlines .

take precedence over Hidden lines take precedence over hidden and centerlines .

Cutting plane lines take precedence over centerlines locating the cutting plane for the section view.

when Centerlines are included in the section view, but hidden lines are omitted .

Certain features of engineering parts are generally not sectioned even though the cutting plane may pass through them.

When the cutting plane passes through the

length

of supporting ribs, lugs, and other thin parts, the feature is represented without section lines to avoid a

misimpression of solidity

.

In addition to thin structural features, parts not sectioned also include standard mechanical elements such as shafts, bolts, screws, nuts, rivets, keys, pins, bearings, and gear teeth . The shaft, bolts, and nuts of the assembly are not sectioned even though they are cut by the cutting plane.

http://www.tarleton.edu/Faculty/tbarker/105/Notes_handout s/Sectioning.pdf

Okay to hatch because the cutting plane is perpendicular to the rib Impression that the entire object is solid

When both a web and ribs are present in section views of cylindrical parts, the

sectioning rule alternate

applies. When ribs are present in addition to the web, the usual convention for ribs would result in a view identical to case A. To eliminate this misrepresentation, in this technique, only alternating section lines are shown in the cross-hatching style.

Ribs in section

not drawn if parallel to plane because tends to imply greater mass than actual, drawn if rib runs perpendicular to plane ,

same true for spokes Conventional Practice

- sectioning not a physical cut , a

graphic cut

- could be different such as ribs not sectioned and spokes not sectioned, also items usually not sectioned: ribs, spokes, bolts, pins, keys

http://www.ateneonline.it/bertoline/docenti/IM/IM_ch8.pdf Conventional practices have been established to handle section views of special situations, such as the alignment of holes, ribs, and spokes.

8.41 Ribs, webs, spokes, lugs and other thin features are not section lined when the cutting plane passes parallel to the feature.

A

rib

or

web

is a thin flat piece that acts as a

support

.

8.42 Adding sections lines to these figures would give the false impression that the part is thicker than it really is .

http://www.ateneonline.it/bertoline/docenti/IM/IM_ch8.pdf 8.43

Occasionally, section lines are added to a thin feature, so that it is not mistaken or read as an open area.

The web could be interpreted as being round (solid) and without ribs. To section line a thin feature, use alternate lines on the feature.

8.44 If the feature is not lost, then the section lines should not be added.

Engineering Drawing and Graphic Technology (Thomas E. French)

Page 161:

5: Parts not sectioned

Many parts (bolts, pins, shafts) recognized easily by their exterior views than by sections. They may lie in the path of the sectioning plane.

Such parts should be left in full view and not sectioned. Otherwise, the drawing will be difficult and confusing to read.

6 A. Spokes not sectioned

Even though the section plane passes through two spokes, sectional view must be made without crosshatching the spokes.

How does one differentiate between them?

Engineering Drawing and Graphic Technology (Thomas E. French)

Page 162:

6 A. Spokes not sectioned

… Other machine elements treated in this manner are teeth of gears and sprockets, vanes and

supporting

ribs of cylindrical parts, equally spaced lugs and similar parts.

B. Ribs in Section

When the cutting plane passes longitudionally through the center of a rib or web, crosshatching of ribs is not performed as if the cutting plane were just in front of them.

Ribs crosshatched gives a

misleading effect

suggesting a cone shape (implies presence of a

lot of material

)

Engineering Drawing and Graphic Technology (Thomas E. French)

Page 162:

6 B. Ribs in Section

… When the cutting plane cuts a rib length or axis direction), it is

transversely

(right angle to its

always cross hatched .

6C. Lugs in Section

A lug (

projecting ear, not crosshatched.

of usually a rectangular cross section ) is

Fig. 30: Small lugs Large lugs (not hatched) (hatched) treated as spokes or ribs.

treated as the solid base of the part.

Pages 161-165: Nice read

Oblique Views

Organization of Lectures and Laboratory Assignments

Topic

Intro and Basic Constructions Orthographic Projections Orthographic Projections Isometric Projections Missing Views Sectional and Assembly

Oblique Projections

Perspective Projections Lines and Planes Lines and Planes Auxiliary Projections Intersection of lines/planes/solids Intersection and Development TOTAL

Week (No. of Lectures)

Week 1 (2) Week 2 (2) Week 3 (2) Week 4 (2) Week 5 (2) Week 6 (2)

Week 7 (2)

Week 8 (2) Week 9 (2) Week 10 (2) Week 11 (2) Week 12 (2) Week 13 (2) 26

Lab

Lab 1 Lab 2 Lab 3 Lab 4 Lab 5

Lab 6

Lab 7 Lab 8 Lab 9 Lab 10 Lab 11 Lab 12 12

TA: PROJECTIONS REMAIN PARALLEL IN ALL THREE TRUE FEATURES

OBLIQUE

SENSE OF DEPTH ORTHOGRAPHIC ISOMETRIC

ANUPAM SAXENA TA101 LECTURE XIII OBLIQUE VIEWS

TA: ROTATED OBJECT TWICE TO CAPTURE IT ON THE PLANE OF SCREEN TA: PARALLEL PROJECTORS ARE PERPENDICULAR TO THE SCREEN ISOMETRIC

ANUPAM SAXENA TA101 LECTURE XIII OBLIQUE VIEWS

TA: PARALLEL PROJECTORS PERPENDICULAR TO THE PLANE WHICH IS PARALLEL TO ONE OF THE PRINCIPAL PLANES OF THE OBJECT ORTHOGRAPHIC

ANUPAM SAXENA TA101 LECTURE XIII OBLIQUE VIEWS

TA: PARALLEL PROJECTORS

OBLIQUE (NOT PERPENDICULAR)

TO THE PLANE

OBLIQUE ANUPAM SAXENA TA101 LECTURE XIII OBLIQUE VIEWS

TA: CHOOSE THE FRONTAL PLANE (E.G.; ONE WITH MANY CIRCULAR/COMPLEX FEATURES) TA: TWO OPTIONS: RETAIN THE DEPTH DIMENSION

CAVALIER

FORESHORTEN THE DEPTH DIMENSION TO HALF

CABINET

Depth direction 30 or 45 degrees

POSSIBLY THE SIMPLEST AMONGST THE THREE SCHEMES OF DRAWING ANUPAM SAXENA TA101 LECTURE XIII OBLIQUE VIEWS

2 holes  20  50 40 200 10  36  30 10 8 20

CAVALIER ANUPAM SAXENA TA101 LECTURE XIII CAVILIER VIEW EXAMPLE

 80  60 8  50  35 8 8 130 4 8

CABINET ANUPAM SAXENA TA101 LECTURE XIII CABINET VIEW EXAMPLE

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