ME2103 Engineering Visualization & Modeling Conventions & Symmetry

By: A/P Lee Kim Seng

Symmetry Symmetry Many engineering components are symmetrical about a centre line or axis, it can often be represented satisfactory by half a view.

To show that a half view has been drawn, two short, thick, parallel lines are drawn across the symmetry demarcation line at each end. (right angle to axis)

To emphasize further, the outlines of the part extend slightly beyond the line of symmetry.

A/P Lee Kim Seng

Symmetry

A/P Lee Kim Seng

Hole ϕ10 This side only

Example of Symmetry

A/P Lee Kim Seng

Shaft bracket body

Example of Symmetry

A/P Lee Kim Seng

Shaft bracket body

Example : Align view of holes

Given

Gives the impression that holes are at unsymmetrical position.

Apply aligned

convention

Example : Example : Align view of ribs

Apply aligned

convention

Conventions Enlarged part views On occasion, components carry features which, in the general scale of the drawing, are too small to be dimensioned clearly.

Such features may be enclosed in thin circle from which a leader is drawn to an enlarged part view.

A/P Lee Kim Seng

Enlarged Part View

A/P Lee Kim Seng

Conventions Repetitive information If identical parts or features appear many times, repeated illustrations of them may be avoided by drawing one, and indicating the positions of the others by their centre lines.

A/P Lee Kim Seng Repeated identical parts or features

Repetitive Information

A/P Lee Kim Seng

Conventional Representation of Knurling

Two types of knurling, straight and diamond knurling, are use and the conventional representation use thin lines. (straight knurling is often used on the heads of hexagon socket cap screw)

A/P Lee Kim Seng

Diamond Knurling in Process

A/P Lee Kim Seng

Knurling Tools

A/P Lee Kim Seng

Conventional Representation of Interrupted Views

Long parts of constant cross-section may be shown by interrupted views.

A piece from the centre of the part is imagined to be removed and the ends of the view are brought together.

Circular section

Tube

Rectangular section

A/P Lee Kim Seng

Conventional Representation of Square End & Bearing

A square end on a shaft is represented by diagonal drawn on the flat face.

A similar convention is used for ball and roller bearing.

Nylon Pulleys

A/P Lee Kim Seng

Conventional Representation of Cylindrical Compression Spring

The helices on a cylindrical compression spring should not be projected but drawn as straight lines. The pitch need not be exact and 2 or 3 coils should be shown at each end.

For diagrams and schematic drawings the representation may be simplified to a single line.

A/P Lee Kim Seng

Conventional Representation of Gear Teeth on the circular view of a gear may be omitted. A thick circle representing the tip of the teeth, and a thin chain circle representing the pitch circle.

A/P Lee Kim Seng

For a rack, one or two teeth are drawn by a thick line representing the tips and a thin line representing roots. The pitch line is not shown.

Conventional Representation of Rack

A/P Lee Kim Seng

Abbreviation of General Engineering Terms for Use on Drawing

A/P Lee Kim Seng

Thank You

A/P Lee Kim Seng