Standards

which it refers. If space is limited, the symbol may be placed on an extension line on that surface or on the tail of a leader with an arrow touching that surface as shown in figure 4-18. When a part is to be finished to the same roughness all over, a note on the drawing will include the direction “finish all over” along the finish mark and the proper number. An example is FINISH ALL OVER³². When a part is to be finished all over but a few surfaces vary in roughness, the surface roughness symbol number or numbers are applied to the lines representing these surfaces and a note on the drawing will include the surface roughness symbol for the rest of the surfaces. For example, ALL OVER EXCEPT AS NOTED (fig. 4-19). Figure 4-18.—Methods of placing surface roughness symbols. STANDARDS American industry has adopted a new standard, Geometrical Dimensioning and Tolerancing, ANSI Y14.5M-1982. This standard is used in all blueprint production whether the print is drawn by a human hand or by computer-aided drawing (CAD) equipment. It standardizes the production of prints from the simplist hand-made job on site to single or multiple-run items produced in a machine shop with computer-aided manufacturing (CAM) which we explained in chapter 2. DOD is now adopting this standard For further information, refer to ANSI Y14.5M-1982 and to Introduction to Geometrical Dimensioning and Tolerancing, Lowell W. Foster, National Tooling and Machining Association, Fort Washington, MD, 1986. The following military standards contain most of the information on symbols, conventions, tolerances, and abbreviations used in shop or working drawings: ANSI Y14.5M-1982 Dimensioning and Tolerancing MIL-STD-9A Screw Thread Conventions and Methods of Specifying ANSI 46.1 MIL-STD-12,C Surface Texture Abbreviations for Use On Drawings and In Technical-Type Publications FIgure 4-19.—Typical examples of symbol use. 4-7