Modern Engineering Drawing Practices 279 Figure 5.7 Spacing of dimensions. Figure 5.5 Application of dimen- sions. Figure 5.6 Grouping of dimen- sions. Figure 5.4 Decimal-inch dimensions. Walsh CH05 8/30/05 9:35 PM Page 279 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Modern Engineering Drawing Practices 280 Chapter Five Figure 5.10 Breaks in dimension lines. Figure 5.12 Leaders. Figure 5.11 Point locations. Figure 5.8 Staggered dimensions. Figure 5.9 Oblique extension lines. Walsh CH05 8/30/05 9:35 PM Page 280 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Modern Engineering Drawing Practices Modern Engineering Drawing Practices 281 Figure 5.15 Dimensioning diameters. Figure 5.14 The intermediate ref- erence dimension. Figure 5.13 Reading directions of dimensions. Walsh CH05 8/30/05 9:35 PM Page 281 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Modern Engineering Drawing Practices 282 Chapter Five Figure 5.16 Dimensioning radii. Figure 5.17 Dimensioning chords, arcs, and angles. Figure 5.18 Tabulated outline dimensions. Walsh CH05 8/30/05 9:35 PM Page 282 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Modern Engineering Drawing Practices Modern Engineering Drawing Practices 283 Figure 5.19 Symmetric outlines. Figure 5.20 Coordinate or offset outline dimensions. Walsh CH05 8/30/05 9:35 PM Page 283 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Modern Engineering Drawing Practices 284 Chapter Five Figure 5.21 Dimensioning round holes. Figure 5.22 Rectangular coordinate dimen- sioning. Walsh CH05 8/30/05 9:35 PM Page 284 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Modern Engineering Drawing Practices 5.1.4 ANSI Y14.5M-1994 (R1999) tolerancing practices Per ANSI Y14.5M-1994 (R1999), tolerances may be expressed as follows: ■ As direct limits or as tolerance values applied directly to a dimension ■ As a geometric tolerance ■ In a note referring to specific dimensions ■ As specified in other documents referenced on the engineering drawing for specific features or processes ■ In a general tolerance block referring to all dimensions on the engineering drawing, unless specified otherwise Modern Engineering Drawing Practices 285 Figure 5.24 Dimensioning repetitive features. Figure 5.23 Polar coordinate dimensioning. Walsh CH05 8/30/05 9:35 PM Page 285 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Modern Engineering Drawing Practices Tolerances on dimensions that locate features of size may be applied directly to the locating dimensions or specified by the positional toler- ancing method. Unless otherwise specified, where a general tolerance note on a drawing includes angular tolerances, it applies to features shown at specified angles and at implied 90° angles, i.e., intersections of centerlines, corners of parts (internal and external), or other obvi- ous areas not specifically shown to have angles other than 90°. 5.1.5 Direct tolerancing methods Limits and directly applied tolerance values are specified as follows: ■ Limit dimensions. The high limit or maximum value is placed above the low limit or minimum value. As a single-line callout, the low limit precedes the high limit, with a dash separating the values. ■ Plus and minus tolerancing. The basic dimension is given first, followed by a plus-and-minus expression of tolerance. ■ Tolerance limits. All tolerance limits are absolute. ■ Dimensional limits before or after plating. For plated or coated parts, the engineering drawing or referenced document will state whether the dimensions are before or after plating; e.g., “Dimen- sional limits apply before plating” or “Dimensional limits apply after plating.” 5.1.6 Positional tolerancing Positional or location tolerancing defines a zone within which the center, axis, or center plane of a feature of size is permitted to vary from the true or exact position. Geometric tolerancing is the general term applied to the category of tolerances used to control form, profile, orientation, location, and runout. 5.1.7 Examples of ANSI Y14.5M-1994 (1999) dimensioning and tolerancing practices Figure 5.25 shows a typical engineering drawing using the ANSI form for dimensioning, tolerancing, and positioning. For a complete description and operational instructions for the use of ANSI standard dimensioning and tolerancing practices, see ANSI Y14.5M-1994 (1999), which may be obtained directly from ANSI, Inc. See Chap. 16 286 Chapter Five Walsh CH05 8/30/05 9:35 PM Page 286 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Modern Engineering Drawing Practices 287 Figure 5.25 Feature control frame placement dimensions per ANSI Y14.5M-1994 (R1999). Walsh CH05 8/30/05 9:35 PM Page 287 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Modern Engineering Drawing Practices for addresses and acronyms of American standards organizations, specification authorities, societies, and institutes. 5.1.8 Design notes on dimensioning and tolerancing From an electromechanical design standpoint, the dimensioning and tolerancing practices used on engineering drawings for the design and manufacturing of parts, subassemblies, and assemblies should take the following points into consideration: ■ Close tolerances add cost to a finished product. ■ The tolerance should be balanced to the function of the part. ■ Arbitrary selection of a general tolerance can cause design and fit problems on the finished product or create unnecessary work. ■ Use care in the selection of bilateral and unilateral tolerances. ■ Remember that modern computer numerical controlled (CNC) turning centers, machining centers, electric discharge machining (EDM) machines, CNC punch presses, and other CNC equipment are capable of producing parts with closer tolerances than were pos- sible in the past. Spindle accuracies are higher and CNC movement controls are very accurate on modern machine tools and equipment. ■ Use tables of preferred limits and fits only when applicable. ■ Select plating thickness limits (range) carefully so as to prevent dimensional interference between mating parts. ■ To control a large tolerance spread owing to many parts in a dynamic assembly, design an adjustment means in the mecha- nism at one or more critical positions. ■ Tooling fixtures and tooled parts help control tolerance ranges to a great extent on assemblies and complex mechanisms. ■ Machined finishes are surface textures and therefore can be con- sidered to have a tolerance [root-mean-square (rms)] value. Therefore, specify only a machined or tooled surface finish that is functional to the part. The experienced electromechanical designer or product design engineer must be proficient in dimensioning and tolerancing prac- tices to be most effective and successful at the design function. Many 288 Chapter Five Walsh CH05 8/30/05 9:35 PM Page 288 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Modern Engineering Drawing Practices [...]... +1.413 –0 .58 8 –0.700 –1 .54 2 –1.879 –2.840 –3.3 45 –4.631 –7 .53 1 –0.392 –0 .57 1 –0.907 –2.278 –0.879 –2.384 –4.211 5. 496 –8.823 –0.281 –0.442 +0.083 +0.083 +0. 656 +0. 656 +0. 656 +0.994 +1 .58 2 +1.660 +2.717 +3.739 +5. 440 +7.701 –0.308 –0.308 –0.971 –0.971 –1.932 –1.932 –3.218 5. 253 0 0 0 0 –0.308 –0.971 –1.933 –3.218 5. 253 +0.290 +0.4 65 +0. 654 +0.990 +1.227 +1 .56 3 +1.048 +1 .56 5 +2. 153 +2. 052 +3.288 +4.310... Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website Walsh CH06 8/30/ 05 9:39 PM Page 297 Source: McGraw-Hill Machining and Metalworking Handbook Chapter 6 Computer-Aided Design, Manufacturing, and Engineering Systems Regardless of what is being produced, the fabrication... dL = 0 + 1 .50 00 dU = 0.001038 + 1 .50 00 dL = 1 .50 000 dU = 1 .50 104 Lower limit for the shaft: Upper limit for the shaft: L3 = CD1/3/1000 L4 = CD1/3/1000 L3 = −1 .54 2 (1 .5) 1/3/1000 L4 = −0.971 (1 .5) 1/3/1000 L3 = −0.0017 651 3 L4 = −0.00111 15 DL = 1 .50 0 + (−0.0017 651 3) DU = 1 .50 0 + (−0.00111 15) DL = 1.49823 DU = 1.49889 Therefore, the hole and shaft limits are as follows: Hole size ϭ 1 .50 000/1 .50 104 diameter... Not for sizes under 0. 95 in Source: J Shigley and C Mischke (eds.), Standard Handbook of Machine Design New York: McGraw-Hill, 1996, p 19.11 The preceding procedures for limits and fits are mandatory practice for design engineers and tool design engineers in order for parts to function according to their intended design requirements Assigning arbitrary or “rule of thumb” procedures for the fitting... or a later revision 5. 1.9 Symbols used in ANSI Y14.5M-1994 (R1999) and ISO dimensioning and tolerancing See Figure 5. 26 for the ANSI and International Standards Organization (ISO) symbols currently used for dimensioning and tolerancing 5. 2 Typical Industrial Design Engineering Drawings There are certain exceptions to the recommended dimensioning and tolerancing practices described in this chapter ■... practice and can create many problems in the finished product Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website Walsh CH 05 8/30/ 05 9: 35 PM Page 2 95 Modern Engineering Drawing Practices Modern Engineering Drawing Practices TABLE 5. 3 2 95 Metric... process nearly always begins with a computer-aided design drawing While paper prints are still a necessity in some instances, the machining and metalworking industries have been transformed by the evolution of computer-aided design (CAD) and computer-aided manufacturing (CAM) systems Two-dimensional drafting packages are largely giving way to three-dimensional solid-modeling packages Although mechanical... The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website Walsh CH06 8/30/ 05 9:39 PM Page 3 05 Computer-Aided Design, Manufacturing, and Engineering Systems Computer-Aided Design, Manufacturing, and Engineering Systems 3 05 Generic features ■ Holes (through, blind, countersunk, counterbored, etc.) ■ Threads ■ Fillets ■ Chamfers ■ Shells (hollowed solids... configured most often with three, four, or five axes of motion Not all CAM packages support fourth- or fifth-axis commands Some CAM packages do support commands for fourth and possibly fifth axes, but they do not allow simultaneous four- or five-axis motion If true simultaneous four- or five-axis motion is needed for a machine, then the CAM vendor should be asked to clarify if this is supported ■ Types... www.ugs.com www.vero-software.com www.type3.com www.wittlockeng.com 8/30/ 05 9:39 PM WE-CIM OPUS CAM EdgeCAM OneCNC SolidCAM SprutCAM SURFCAM CAMWorks, ProCAM NX Machining VISI-Series Type3 Walsh CH06 Page 313 Computer-Aided Design, Manufacturing, and Engineering Systems 313 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies . precision work at slow speeds and light pressures, but are not suited for temperature differences. RC4 Close running fits are intended for running fits on accurate machinery with moderate speeds and pres- sures concur with ANSI B4. 2-1 978 (R1 999) for the metric standard. The U.S. Customary standard for preferred limits and fits is ANSI B4. 1-1 967 (R1 999). Modern Engineering Drawing Practices 293 Walsh CH 05. forces required are not practical. Walsh CH 05 8/30/ 05 9: 35 PM Page 2 95 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill