Introductory and Standards Chapter One Introductory and Standards Information

Purpose This chapter provides an overview of how to: select a range of instruments suitable for drafting understand the use of letters, numerals, abbreviations and line types choose 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.

Select a range of instruments suitable for drafting 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

Select a range of instruments suitable for drafting 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

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

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

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

Choose drawing layouts, paper size and scales 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.

Fig 1.15 (c) Fig 1.15 (a)

Choose drawing layouts, paper size and scales 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.

Choose drawing layouts, paper size and scales 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.

Choose drawing layouts, paper size and scales 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.

Choose drawing layouts, paper size and scales 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.

Choose drawing layouts, paper size and scales 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.

Summary 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.