Basic Engineering Drawing Definitions and Practices

A1.0a Introduction

The course material contained in this workbook is designed to be taught over a 13-week period of time. Assignments are numbered in alpha-numeric order. For example, A1.1 is the first assignment relating to hand-sketched drawings…A1.1a, A1.1b, etc. are pages of instruction relating to A1.1; C1.1 is the first assignment relating to solid modeling…C1.1a is the first page of instruction relating to C1.1, etc. Sketching assignments in week 13 are numbered A13.1, A13.2, etc. Solid modeling assignments in week 13 are numbered C13.1 C13.2, etc.

Chapter 1 contains very basic engineering drawing definitions and practices. This material reviews, refreshes and expands on topics that many freshman college students have already taken in high school or community colleges. This review assures that all students have a common base in graphics so that we can quickly move into more advanced geometric topics required to model 3-dimensional objects.

The final product of the engineering design process is a 2-dimensional engineering drawing. This becomes the “instrument of communication” between the designer and all members of a manufacturing facility. All of the geometric information required to make the object function must be properly displayed on this 2-dimensional hard copy drawing or on a 2-dimensional computer screen. All assignments in this workbook are supposed to be submitted in the form of 2-dimensional drawings.

In order to represent 3-dimensional parts in 2-dimensional drawings, pictorials are often included in the drawing so that engineers can understand the complicated 3-dimensional part better. Pictorials are different from camera images. In the oblique view, for example, receding axes are drawn at a different angle. In pictorials it is important to understand which lines are in the true length and which shapes are in the true shape. In assignments A1.2 and A1.3, students will practice isometric and oblique sketches.

Technical drawings are communication tools. Thus, all information in the drawings must be accurate and clear. Students are expected to understand the basic rules of technical drawings, such as how to distinguish a visible line from a hidden one, how to write the dimensions of lines and circles, how to write machining notes, etc.

An orthographic view is a projection of a part or assembly in a plane with parallel projectors. It is used to describe the part or assembly accurately and clearly on the projected plane. In general, six orthogonal planes are available. The most commonly used orthographic view is the three-view, including front, top, and right-side views. In assignment A1.4 students will practice projecting a guide block to six orthographic views.

In the solid modeling assignment, students will be exposed to the basic layout of a drawing and practice various views, including isometric, oblique, and perspective views. At this point students are not expected to create a solid model. They will learn the basic functions of a solid modeler, such as writing notes, showing/hiding various symbols in a particular solid modeling program.

A1.1a Drawing Instruments

SKETCHING SUPPLIES

2 Pencils H (soft) 4H (hard)

2 Erasers soft hard

3 Scales with graduations in… …1/8”, 1/10”, mm

2 Triangles 45/45 30/60

Compass

Dividers

Protractor

Erasing Shield

Sanding Block (pencil sharpener)

OPTIONAL …

Parallel Glider

Ames Lettering Instrument

Templates, circles, ellipses

A1.1b Uppercase Vertical Lettering

Letters are composed of single stroke lines and arcs, having proportions based on a 6 × 6 grid, and are formed in a manner as illustrated in A, C, D, and numeral 5. The letter I is a single stroke.

Letters A, M, O, Q, T, V, X, Y are 6 units wide; letter W is 8 units wide.

Letters B, C, D, E, F, G, H, J, K, L, N, P, R, S, U, Z, & are 5 units wide.

Letters A, E, F, H, I, K, L, M, N, T, V, W, X, Y, Z are based on straight lines only.

Letters C and O are based on circular arcs.

Letters B, D, G, P, Q, R are based on straight lines and circular arcs.

Letters J and U are based on straight lines and an elliptical arc.

Numerals 1, 4 are based on straight lines only.

Numerals 2, 5, 7 are based on straight lines and elliptical arcs.

Numerals 0, 3, 6, 8, 9 are based on elliptical arcs only.

Numerals 2, 3 and the letter S are based on the numeral 8.

Numerals 8 and 9 are based on the numeral 0.

Numeral 8 is based on 2 ellipses,

A1.2a Isometric & Oblique Views

A1.2b Pictorial Sketching Exercises

DIRECTIONS: Sketch the following objects full size on isometric or oblique grid paper. Arrange the objects on assignment sheets as directed below. The distance from grid point to point is .50”

This exercise is to be freehand. DO NOT USE A STRAIGHTEDGE.

A1.2 Isometric sketching

Assignment sheet A1.2 shows an example of an isometric drawing of a right triangular block, 1.0” × 2.0” × 0.5” thick, resting on the 1.0” × 2.0” face. Also shown is a 1” dia. circular rod, 2” long, resting on the circular end. Sketch the following 2 objects showing an isometric view on the grid provided in A1.2.

1) A 1.5” thick wedge with its top and bottom faces in the form of a 1.5” × 2.0” × 2.5” triangle

2) A 1.5” diameter cylinder, 3.0” long, resting on its side.

A1.3 Oblique sketching

Assignment sheet 1.3 shows an oblique cylinder, 1.0” dia. × 2.0” high resting on its circular base. Sketch objects as described below.

1) Sketch an oblique cylinder 1” dia. × 2.0” long lying on its side. Choose a view to show the circular end as true shape.

1) A 2” × 3” × 3” triangular rod, 2.5” long, resting on the 2” side. Choose a view to show the triangular end as true shape.

1. SKETCHING MODES

1.1 Schematic

1.2 Orthographic

1.3 Pictorial

1.31 Isometric, Dimetric, Trimetric, Axonometric

1.32 Oblique

1.33 Perspective

1.331 1 Point Perspective

1.332 2 Point Perspective

1.333 3 Point Perspective

1.334 Internal Perspective

2. REALISM

2.1 Proportion

2.2 Perspective

2.3 Details…features, shading, color

A1.2 Isometric Sketching

A1.3 Oblique Sketching

A1.4a Elements of a Working Drawing

A1.4b Views, Conventions… …and Projection Systems

VIEWS AND CONVENTIONS

SEE illustrations in TEXT for the following topics

Principal Views, Top, Front, Right Side

6–view Orthographic projection

Unnecessary views

Simplified views

Revolved views

Removed views

Partial views

Space saving views

Conventional breaks

Curve plotting

Conventional views – – – 2 holes replace 3, 4, 5 holes etc.

Conventional views – – – 2 ribs replace 3, 4, 5 ribs etc.

Conventional slots and holes through pins and screws

Intersection of Cylinders; good and poor practice

Fillets and rounds

Runouts

A1.4c Guide Block

GIVEN: Isometric pictorial of a Guide Block.

REQUIRED: On the grid sheet provided, sketch six orthographic views. Both holes extend all the way through the block. The hole is one increment in diameter, and the counterbore and countersink are two increments in diameter. The Cbore is 1/2 increment deep. Use the bold points on the grid to locate the front view. DO NOT use a straight edge.

A1.4 Six Orthographic Views of Guide Block

J1.4

X1.4

C1.1a Drawing Views, Formats, Notes

1. Download the Coupling C11X01.prt

2. Use this part to generate the views illustrated...