Boundy8e ppt ch01

Copyright 2012 McGraw-Hill Australia Pty Ltd PPTs t/a Engineering Drawing 8e by Boundy 1-1

Chapter One

Introductory and StandardsInformation


Purpose

This chapter provides an overview of how to:select a range of instruments suitable for draftingunderstand the use of letters, numerals, abbreviations and line typeschoose drawing layouts, paper size and scales


Select a range of instruments suitable for drafting

The advent of CAD (computer-aided drafting) has not diminished the need for a range of quality equipment to produce a commercial standard of drafting/sketching required in industry.



Essential items include: Pencils (clutch and/or wood – cased) Scale rule Eraser and erasing shield Drawing set French curves Circle and ellipse template Adhesive tape

Fig 1.6



1.2 Drawing instruments pp.4–6 (Boundy, A.W., 2012) illustrates

the essential drafting items; however, always consult your teacher/instructor for advice on the range and quality required to meet your particular learning needs.


Understand the use of letters, numerals, abbreviations and line types

1.3 Letters and numerals

p.8 (Boundy, A.W., 2012) The basic form for letters and numbers are

demonstrated in Figure 1.12, p.7. The height (h) of characters pertaining to

particular sheet sizes is stated in Table 1.2, p.8.

Characters should be spaced twice the letter line thickness or 1mm, whichever is greatest.


Figure 1.12



General rules for character usage: Use upper case letters (except for standards,

e.g. kg) Only use one style of character per drawing Use vertical characters for titles, drawing

and reference numbers Avoid underlining Characters should be kept clear of lines

unless essential to drawing.


1.4 Types of line The types of line which are commonly used

in engineering drawings are illustrated in Table 1.3., p.9.

Generally, thick dark lines apply to outlines (so they stand out) and the rest (e.g. dimension, hidden, short break etc.) are thin light lines with some exceptions combining both thick and thin (e.g. cutting plane).



The usage of line types is illustrated in Figure 1.14, p.10.

Table 1.4, p11 groups specific line type thicknesses per metric sheet size in reference to Table 1.3. (e.g. Type A continuous line {table 1.3} is 0.7 thick for A0, B1 {table 1.4} sheet size.)



Choose drawing layouts, paper size and scales

1.6 Scales, p.10 Scale – a ratio of drawn size to actual size. Ratio chosen should still allow easy

interpretation of drawing information. AS1100.101 – 1992 identifies scale ratios

used in Engineering and architectural drawings (e.g. shown in Boundy, 2012: p.10).

Scale used should be recorded near or in the title block.

A note ‘not to scale’ or ‘NTS’ indicates drawing is not scaled.



1.7 Sizes of drawing paper Based on A0 size as recommended by

Standards Australia. A ratio of 1 : exists between the various A

size papers (see Figure 1.15 on next slide). The B series sheet sizes are intermediate

sheet sizes between the A series (ref. Figure 1.15 (b), p.12).

Drawing sheets can also be cut from standard rolls (860mm and 610mm) to suit individual drawings.

2


Fig 1.15 (a)

Fig 1.15 (c)


1.8 Layouts of drawing sheets

pp.11–15 AS1100.101 clause 2.5 identifies standard

drawing sheet layouts for all sheet sizes. Figures 1.16 and 1.17 p.13 (Boundy, 2012)

show typical layouts of A1 and A2 sheets. Sheet size designation will preferably be

indicated at the right-hand bottom corner of drawing frame.



Drawing layouts should include: system of projection (1st or 3rd angle) drawing units, i.e. ‘all dimensions in

millimetres’ the drawing standard followed, i.e. AS1100 drawings prepared for microfilming should

indicate the drawing frame dimensions or a graduated line at least 150mm long.



Information relating to layouts are normally recorded in or near the title block at the bottom right – hand corner of the drawing frame (Figure 1.18, p.14 in Boundy illustrates examples).

Drawing frames are spaced in from the edge of a sheet, Figure 1.15(d) and Table 1.5 (Boundy, 2012) identify necessary detail.



Material or parts lists attached to title blocks are included when a sheet contains several parts or an assembly is shown and include information such as part number, name, quantity, material, drawing reference number, etc.

Material or parts list may be placed on a separate sheet when the list of parts is extensive or if its more convenient to do so.



When changes occur on a drawing they should be recorded on a revision table normally located at the top right hand corner of the drawing frame.

To assist in locating features on a drawing, zones are located inside the drawing frame; horizontal zones are designated by capital letters, while vertical zones are numerical.

Table 1.6, p.15 (Boundy, 2012) detail the number of zones and widths of margins per sheet size.



To draw effectively you need appropriate resources, follow standard forms of representation, such as line types, understand the use of scaling as relating to sheet size and record relevant information pertaining to the drawing effectively.

Summary

Boundy8e ppt ch01

Education

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