technical drawing i

Engineering Drawing–I

Graphics Language

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1. Try to write a description of this object.

2. Test your written description by having someone attempt to make a sketch from your description.

Effectiveness of Graphics Language

The word languages are inadequate for describing the

sizesize, shapeshape and featuresfeatures completely as well as

concisely.

You can easily understand that …

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Purpose of an Engineering Drawing1. An engineering drawing is not an illustration.2. It is a specification of the size and shape of a part or assembly.3. The important information on a drawing is the dimension and

tolerance of all of its features.

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PROJECTION METHOD

PROJECTION METHOD

Perspective

Oblique Orthographic

Axonometric Multiview

Parallel

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Disadvantage ofPerspective Projection

Perspective projection is notnot

used by engineer for manu-

facturing of parts, because

1) It is difficult to create.

2) It does not reveal exact

shape and size. Width is distorted

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Orthographic Projection

Orthographic projection

• Orthographic" comes from the Greek word for "straight writing (or drawing)." This projection shows the object as it looks from the front, right, left, top, bottom, or back, and are typically positioned relative to each other according to the rules of either “First Angle” or “Third Angle” projection.

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Image of a part represented in First Angle Projection

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Image of a part represented in First Angle Projection

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Image of a part represented in First Angle Projection

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The first drawing is the front view (drawn looking straight at the front of the L-shape), the second is a drawing of the L-shape seen from the side (known as side view) and last of all a drawing from above known as a plan view. The red lines are faint guidelines and they are drawn to help keep each view in line. level and the same size.

THE FRONT VIEWNow imagine standing directly in front of the L-shape, the drawing opposite shows exactly what you would see.

THE SIDE VIEWImagine standing directly at the side of the L shape.

THE PLAN VIEWThe plan view is a view seen directly from above. Some people call this a birds eye view.

Orthographic / Multiview• Draw object from two / three perpendicular views

/ Orthographic

What it looks like pictorially

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