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Computer Aided Drawing MTS242

Muhammad Usman Rafique

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Lecture 6

Material Symbol andFinish

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Organization

Announcement

Sheet Division

Assignment 2

Tolerance

Reading Assignment

Surface Finish

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Course OutlineWeek Topic

1 Introduction

2 Types of Lines, Uses, Geometrical Construction

3, 4Projection Systems, Orthographic Projection, 1st Angle Projection, 3rd

Angle Projection

5 Dimensioning and Tolerances

6 Material Symbol and Finish

7 Sectional Views

8 Introduction to CAD / CAM

9 Drawing in AUTOCAD

10 Labeling the drawing in CAD

11 Mid-Term Exam

12 Auxiliary Views

13 Pictorial Representations

14 Assembly Drawings

15 Electronic Drawings

16 Introduction to Pro-Engineer

17 Revision

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Announcement

Telephone Extension : 470

Email : usman.rafique@mail.au.ed.pk

Website: http://sites.google.com/site/mtsengg/

Students may come to my officeIAA Block, 1st Floor,Room 116

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Assignment 2

Explain in YOUR OWN WORDS (and sketches) Multi-View Drawing Orthographic Projections 1st angle and 3rd angle projection, their theory and how 3 views are

chosen from them

Why do we use orthographic projection

You may consult text book, library or internet.

Copying anything is NOT allowed. Any copied portion will lead to ZEROpoints

Deadline: Monday 25th October, 2010

0900 Hours

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Sheet Division

Explained on white board

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Tolerances

Introduced last week - More detail today

Tolerances

Universal Tolerance:

All dimensions have same tolerance level

For example All tolerances to be 1mm

Specific Tolerance: Different tolerance levels for different features

Mentioned with dimensions of the features

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Tolerances

Methods of writing tolerances

Nominal Value followed by tolerance

Maximum and minimum values

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Tolerances

Dimensioning the tolerances

Unilateral Tolerances

Bilateral Tolerances

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Reading Assignment

Chapter 13, Fundamentals of Engineering Drawing byWarren J. Luzadder (11th Edition)

Topics: Tolerances(13.21) to Profile Tolerancing(13.34)

No need to memorize. But go through it and be familiar with

symbols and conventions

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Surface Finish

Surface of material is never perfect

Inaccuracies or imperfections is surfaces are called

Surface Finish (SF)

Caused by tool shape and its direction of motion

Important in some cases - hence must be mentioned indrawing

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Surface Finish

Roughness and Waviness Roughness: Created by tool marks

Waviness: Variation in dimension

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Surface Finish

Mentioning SF on drawing

Putting a Tick Symbol on the surface

Tick comprises of 2 lines, at 60 Deg to each other

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Surface Finish

Mentioning SF on drawing

Symbol of Machining

Closed Tick

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Surface Finish

Mentioning SF on drawing

Machining NOT allowed

A circle placed over Tick

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Surface Finish

Mentioning SF on drawing

Additional Information

Add extension to tick

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Surface Finish

Mentioning SF on drawing

Finishing Requirement applied to all four surfaces

Add a circle on extension

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Surface Finish

Finishing Requirement applied to all four surfaces In orthographic Views

SF applicable to all

boundaries of Front

view

Front and Back faces

have different SF

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References

Engineering Drawing for Manufacture by Brian Griffiths,

Feb 2003, Elsevier Science and Technology Books