STANDARD DRAFTING PRACTICES DRAFTING PRACTICES Machinery's Handbook, 31st Edition
620
While there are many national standards-based drafting practices throughout the world, three sets of standards practices predominate internationally. These sets of prac- tices include the American National Standards Institute (ANSI); American Society of Mechanical Engineers (ASME); those modeled on standards developed by the Interna- tional Organization for Standardization (ISO); and to a lesser extent, those based on Jap- anese Industry Standards (JIS). However since JIS has committed to adopting ISO prac- tices, coverage will be limited to ANSI/ASME practice and select ISO practices where appropriate. In general, there are several ANSI/ASME Standards for use in preparing engineering drawings and related documents. Standard Drafting Practices Sizes of Drawing Sheets.— Recommended trimmed sheet sizes are shown in Table 1. Customary inch sizes are documented in US ANSI/ASME ANSI/Y14.1-2012, are based on commercial letterhead paper (8 1 ⁄ 2 3 11 in.), and are in general use throughout the United States. Each successive size beginning with 8 1 ⁄ 2 3 11 in. (A) is double the size of the previous (except size F). Using sizes based on commercial letterhead paper size, and its multiples, permits filing small prints and folded larger prints in the same commercial standard letter files. For drawings requiring trimmed metric sheets, sizes are based on ANSI/ANSI/ASME Y14.1M-2012 in the United States and ISO 5457 in other countries. Metric sizes are consistent across US and ISO standards. As with the customary inch sheet sizes, each successive metric size sheet beginning with commercial letterhead paper size A4 is double the previous size also for ease of folding and filing. Metric sizes are based on the width-to-length ratio of 1 to 2 . Note that the metric size designators increase as the paper decreases in area. Virtually all CAD systems include both inch and metric size paper templates. Most countries outside the United States use metric paper sizes, so for foreign correspondence it is recommended that the metric sheet sizes be used. For additional sizes and details see the respective standards. Table 1. Drawing Sheet Sizes
US Customary Size, inches ( ANSI/ASME Y14.1-2012 )
Metric Size, millimeters ( ANSI/ASME Y14.1M-2012 )
A B
D 22 3 34 A4 210 3 297 A1 594 3 841 E 34 3 44 A3 297 3 420 A0 841 3 1189
8 1 ⁄
2 3 11
11 3 17 17 3 22
C F 28 3 40 A2 420 3 594 Line Conventions and Drawings.— American National Standard ANSI/ASME Y14.2- 2014 establishes line and lettering practices for engineering drawings. The line conven- tions and the symbols for section lining are as shown in Table 2 and Table 3. Approximate width of THICK lines for metric drawings is 0.6 mm, and for inch draw ings, 0.032 inch. Approximate width of THIN lines for metric drawings is 0.3 mm, and for inch drawings, 0.016 inch. These approximate line widths are intended to differentiate between THICK and THIN lines and are not values influencing acceptance or rejection of drawings. Basic line conventions in ISO are established in ISO 128-20: 1996. Lines intended to comply with ISO standards use widths of 0.13 mm, 0.18 mm, 0.25 mm, 0.35 mm, 0.5 mm, 0.7 mm, 1 mm, 1.4 mm and 2 mm, but again may deviate as long as lines are consistent in width and it is possible to differentiate “unambiguously” between two adjacent lines with different widths.
Copyright 2020, Industrial Press, Inc.
ebooks.industrialpress.com
Made with FlippingBook - Share PDF online