Fundamentals of Mechanical Drafting 1

This textbook uses a visual approachto learning how to read, plan, anddraw mechanical drawings. Studentswill study and visualize how a drafterwould solve layouts for a drawing.

Industry requires many millions ofdrawings every year. Every part musthave a working drawing. Thesedrawings communicate the details to askilled craftswoman or man so the itemcan be correctly manufactured. It hastaken more than 100,000 workingdrawings to be able to manufacture thespace shuttle.

The people who make these drawingsare called drafters. There are severaldifferent levels within the draftingprofession:

1. Chief designers create, plan, anddraw designs with the engineersand scientists.

2. Senior detailers make the difficultand more complicated drawings.

3. A checker looks for errors andrequested ECO's (engineeringchange orders).

4. A detailer makes the neededchanges on existing drawings.

5. The drafter does most of sketches,manual drafting, and CADdrawings.

UNIT 1AN INTRODUCTION TO DRAFTING

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The basic tools of mechanical drafting are shown in the illustrations below. These are the tools that thebeginner must have. For advanced drawing techniques, additional equipment will be necessary.

DRAFTINGEQUIPMENT

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The dimension for a hole or a cylinder is indicated by giving its diameter (∅∅).The dimension for an arc is indicated by giving the radius (R) of the arc.

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There are two kinds of oblique drawings: cavalier and cabinet. A cavalierdrawing and a cabinet drawing are drawn in the same manner, except that acavalier drawing is always made to the exact measurements of the object. In acabinet drawing, receding surfaces are drawn one-half size.

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Three types of thread symbols. The simplifiedsymbol is preferred.

Profiles of 10 types of threads

Parts of External Threads Types of External Threads

External Thread Symbols

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Exploded views are pictorial drawings showing all the parts of the item in theirorder of assembly. Generally, they are drawn on a 30° axis in isometric drawings.

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