McGraw-Hill Machining and Metalworking Handbook 3rd ed - R. Walsh_ D. Cormier (McGraw-Hill 2006) WW Part 8 pps

the mechanical action of abrasive particles of irregular shape, size, and hardness. Grinding can be a rough or a precision operation for producing smooth surfaces, either flat, cylindrical, or irregularly shaped. The medium of the grinding operation is the grinding wheel, which is used for both external and internal grinding procedures. Grinding wheel shapes and other specifications are defined by the following ANSI standards: ANSI B74.2-I982, Shapes and Sizes of Grinding Wheels ANSI B74.3-I986, Shapes and Sizes of Diamond and Cubic Boron Nitride Abrasive Products ANSI B74.I3-I990, Markings for Identifying Grinding Wheels and Other Bonded Abrasives Other ANSI standards define chemical analysis, bulk density, size of abrasive grains, and other specifications for grinding products and testing procedures. An ideal grinding abrasive has the ability to fracture before serious dulling occurs and offers maximum resistance to point wear. Each abrasive has a special crystal structure and fracture characteristics, making it suitable for grinding operations on specific materials. Grinding wheels are composed of abrasive grains of preselected size bonded together with different bonding media. Five important Machining, Machine Tools, and Practices 489 Figure 7.112 A modern removable-insert boring head. Walsh CH07 8/30/05 9:48 PM Page 489 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. Machining, Machine Tools, and Practices considerations must be given to the selection of a grinding wheel to suit a particular application: 1. Abrasive type 2. Grain size 3. Bonding media 4. Grade or hardness of the wheel 5. Structure Wheel abrasives Natural abrasives. Corundum, emery, and diamond (corundum is natural aluminum oxide containing varying amounts of impu- rities). Manufactured abrasives. Synthesized diamond, silicon carbide, aluminum oxide, and cubic boron nitride (CBN). These abrasives all have well-defined physical and chemical characteristics. Grain size. Abrasive grains vary from 6 to 8 coarse grit to 1000 to 2000 grit for polishing and lapping. Designation of grinding wheels. A standard marking system defined by ANSI 74.13-1990 for the identification of grinding wheels (exclud- ing diamond and CBN) is shown in Fig. 7.113. From this marking system, you may determine the characteristics of the grinding wheel from its markings. A standard marking system defined by ANSI B74.3-1986 for the identification of diamond and CBN is shown in Fig. 7.114. From this marking system, you may determine the characteristics of diamond and CBN grinding wheels. Grinding wheel speeds. The most efficient operating speeds in surface feet per minute (sfpm) for general use are summarized in Fig. 7.115. The manufacturer of your particular wheel may recommend a differ- ent surface speed based on its experience with its product. Too low a speed will result in wasted abrasive and lower efficiency, and too high a speed may result in too hard grinding action and breakage of the grinding wheel. Do not exceed the maximum speed in revolutions per minute that is marked on each wheel. Severe injury can result from the flying fragments of a broken grinding wheel. 490 Chapter Seven Walsh CH07 8/30/05 9:48 PM Page 490 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. Machining, Machine Tools, and Practices Figure 7.113 Grinding wheel marking system. 491 Walsh CH07 8/30/05 9:48 PM Page 491 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. Machining, Machine Tools, and Practices Figure 7.114 Marking system for diamond and CBN. 492 Walsh CH07 8/30/05 9:48 PM Page 492 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. Machining, Machine Tools, and Practices Some of the standard shapes of grinding wheels are shown in Fig. 7.116. ANSI B74.2-1982 defines shapes and sizes, although different forms and shapes may be produced by some wheel manu- facturers. Standard types and shapes of diamond or CBN grinding wheels are shown in Fig. 7.117. As can be seen from these figures, many shapes and sizes are available for a multitude of grinding operations, from roughing to tool and die finishes. It is difficult in a modern machining and metalworking hand- book to give the exact type or number of grinding wheel to use for any specific application because of the many variables that arise in actual production situations. The data given in this section are for reference and approximate applicational uses. The manufacturer of the grinding wheels and abrasives employed should be contacted for precise applications on any grinding operation. Modern machine grinding equipment has been developed to a high degree over the past 40 years. Figure 7.118 shows a modern surface grinder used in tool and die making and other precision applications. In this machine, the grinding wheel is stationary, and the table tra- verses from left to right and reverses itself in a continuous travel until the final finish is produced on the workpiece. The grinding wheel moves vertically in exact increments to produce the required cut and surface finish. This type of machine is used for flat-surface grinding only. Machining, Machine Tools, and Practices 493 Figure 7.115 Grinding wheel speeds. Walsh CH07 8/30/05 9:48 PM Page 493 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. Machining, Machine Tools, and Practices Figure 7.119 shows a Brown and Sharpe cylindrical grinding machine in which the workpiece is rotated at the same time the grinding wheel is making the required surface finish on the cylin- drical part. The final quality or surface texture of machined and ground parts is usually given on the engineering drawing in root mean square (rms) numbers. An illustration of the finish texture accord- ing to the rms system is shown in Fig. 7.120. These finishes range from 500 to 2 rms, with the numbers representing microinches (␮in) average. 500 rms would represent a roughing operation on a milling machine or shaper to a superfinishing operation of 2 ␮m, average or rms (root mean square). Finishes finer than 2 rms can 494 Chapter Seven Figure 7.116 Standard grinding wheels. Walsh CH07 8/30/05 9:48 PM Page 494 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. Machining, Machine Tools, and Practices be made using polishing compounds such as cerium oxide or rouge. Cerium oxide and rouge are used extensively in the optical industries for polishing lenses and reflecting mirrors. For finishes of higher rms values (ranging from 5 to 3 ␮in), compounds such as aluminum oxide powder may be used. A convenient table of surface feet per minute converted to revo- lutions per minute of the grinding wheel is shown in Fig. 7.121. The figures in the table may be calculated using the following equation for converting surface feet per minute (sfpm) to revolutions per minute (rpm): sfpm rpm and rpm sfp == πD() ( 12 12 mm) πD Machining, Machine Tools, and Practices 495 Figure 7.117 Diamond and CBN wheels. Walsh CH07 8/30/05 9:48 PM Page 495 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. Machining, Machine Tools, and Practices Figure 7.118 Modern automatic surface grinder. Figure 7.119 Cylindrical grinding machine. 496 Chapter Seven Walsh CH07 8/30/05 9:48 PM Page 496 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. Machining, Machine Tools, and Practices Characteristics of grinding Wheel speed. As wheel speed is increased, less work is required of each individual abrasive grain, and this promotes slower wheel wear. Work speed. This is the speed at which the workpiece traverses the wheel or rotates about a center. In-feed rate. The rate at which the wheel enters the workpiece during the grinding action. High in-feed rates increase wheel wear and produce a rougher finish than low in-feed rates. Traverse or cross-feed. This is the rate at which the workpiece is moved across the face of the wheel. It is not the same as work speed. Material to be ground. Materials to be ground are either metallic or nonmetallic, and the metallics are divided into low- or high-tensile types. Aluminum oxide wheels generally are used for grinding metallic materials, whereas diamond and CBN are used to grind the extremely hard metallics, as well as ceramics and other hard nonmetallics. Silicon carbide wheels generally are used to grind the Machining, Machine Tools, and Practices 497 Figure 7.120 Surface roughness gauges. Walsh CH07 8/30/05 9:48 PM Page 497 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. Machining, Machine Tools, and Practices Figure 7.121 Rpm/surface-speed table. 498 Walsh CH07 8/30/05 9:48 PM Page 498 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. Machining, Machine Tools, and Practices [...]... speeds Figure 7.122 gives the approximate honing speeds for cast irons and steels, which are the most commonly honed materials The combined rotation and reciprocation of a hone produces a cross-hatched surface finish on an internal cylindrical part Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved... the American-pattern standard machinist’s files and their common uses and characteristics Figure 7.124 shows the standard Swiss-pattern files with their characteristics and uses Files are characterized by coarseness grade and type of cut Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use... 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 CH07 8/ 30/05 9:49 PM Page 5 08 Machining, Machine Tools, and Practices 5 08 Chapter Seven ■ Straight ■ 30° diagonal right-hand and left-hand (in sets to produce a diamond pattern)... critical 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 CH07 8/ 30/05 9:49 PM Page 511 Machining, Machine Tools, and Practices Machining, Machine Tools, and Practices 511 Thred Kut Heavy-duty brown sulfochlorinated cutting oil,... Sulfur-base cutting oils Used for all metals and high-alloy steels Kleen Kut soluble oil Water-soluble emulsion; economical; mixed with water at 5% to 10% concentration Thred Kut 99 A dark, heavy sulfochlorinated fatty oil for machining and grinding soft, tough, and stringy metals such as stainless steels, low-carbon steels, jet-engine alloys, and monel metals Trampol-X cutting fluid Economical, water-soluble,... The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website Walsh CH07 8/ 30/05 9:49 PM Page 5 18 Machining, Machine Tools, and Practices Figure 7.139 Right-angle notch Figure 7.140 Right-angle notch Figure 7.141 Width of notched opening Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill. .. CH07 8/ 30/05 9: 48 PM Page 501 Machining, Machine Tools, and Practices Machining, Machine Tools, and Practices 501 Figure 7.122 Honing speeds Honing abrasives Honing sticks are produced with the following abrasives: silicon carbide, aluminum oxide, CBN, and diamond Silicon carbide is used to hone cast irons and nonferrous materials, aluminum oxide is used to hone steels, and diamond and CBN are used on... CH07 8/ 30/05 9: 48 PM Page 503 Figure 7.123 Machinist’s files Machining, Machine Tools, and Practices 503 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 CH07 8/ 30/05 9:49 PM Page 504 Figure 7.124 Swiss-pattern files Machining, ... tool and die operation that requires precise division of a circle 7.13 Taps and Dies for Threading Operations The tapping of threaded holes and the die cutting of external threads with the use of taps and dies are performed most efficiently and ecoDownloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved... 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 CH07 8/ 30/05 9:49 PM Page 509 Machining, Machine Tools, and Practices Machining, Machine Tools, and Practices 509 Figure 7.127 JIC carbide code the modern cutting fluids are supplied . include ■ Helical hooded dressers ■ Abrasive wheel dressers ■ Single-stone diamond dressers ■ Multiple-point diamond dressers ■ T-type diamond hand dressers ■ Diamond-stick dressers (silicon carbide) ■ Dressing. cylindrical radius end, flame, oval, 14° taper radius end, tree-shape pointed end, and treeshape radius end. Both rotary files and burrs are made in single-cut and double- cut forms, with various degrees. evolved around the early cemented and sintered carbide grades, no provision was made for the newer, more advanced cutting tool materials. Also, the wide variety of cemented carbide compositions prevented