DRAWINGSTANDARDS

AUSTRALIAN STANDARDS

Engineering drawing is the main method of communication between all persons concerned with the design and manufacture of components; the building and construction works; and engineering projects required by management or professional engineering staff.

the practice of drawing is in many ways so repetitive that, in the interests of efficient communication, it is necessary to standardise methods to ensure the desired interpretation.

Standards Australia has recommended standards for drawing practice in all fields of engineering and these are set out in their publications AUSTRALIAN STANDARDS (AS) 1100 (Technical Drawing) Parts 101 (General Principles) and 201 (Mechanical Drawing).

TERMS AND DEFINITIONS

SHEET SIZES

SCAN PG 174 ATG SHEET SIZES

DRAWING SHEET LAYOUT

SCAN PAGE 175 ATG LINK ARROW TO HEADING AND POINTS.

DIMENSIONING TECHNIQUES

POINTS TO BE OBSERVED WHEN DIMENSIONING

Provide enough dimensions to indicate size and position of all features.

Avoid over dimensioning.

Avoid placing dimensions on hidden details.

Avoid dimensioning features on sectional views other than those for which the section was drawn.

Show all centre lines of symmetry.

Avoid using a line of the drawing as a dimension or extension line.

Keep all dimensions outside the outline of the view.

Dimension circles as diameters and arcs as radii.

Dimensions should read from the shortest to longest from the outline.

Dimensions are read from the bottom or the right hand side of the page.

ALIGNED DIMENSIONING SYSTEM

SCAN PG177 ATG

UNIDIRECTIONAL DIMENSIONING SYSTEM

SCAN PG177 ATG

STAGGERED DIMENSIONS

Where a number of dimensions are close together they should be staggered to ensure clear reading.

OVERALL DIMENSIONS

When a length consists of a number of dimensions, an overall dimension may be shown outside the dimensions concerned. The end projection lines are extended to allow this. When an overall dimension is shown, however, one or more of the dimensions that make up the overall length is omitted. This is done to allow for variations in sizes that may occur due to production. The dimension omitted is always a non-functional dimension. eg. One that does not affect the function of the product.

AUXILARY DIMENSIONS

When all the dimensions that add up to an overall length are given, the overall dimension

may be added as an auxiliary dimension. This is indicated by enclosing the dimension in brackets.

Auxiliary dimensions are never toleranced and are in no way binding as far as machining

operations are concerned.

DIMENSIONING DRAWING FEATURESDIAMETERS

The symbol Ø may be used to precede the figure indicating a hole or cylinder.

End View

Side View