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Figure 15-8.—Grid for heat-treating furnace. high temperatures, and supports the heating elements and the hearth plate. Hearth plates are placed on the bottom of the heating chamber to support the pieces being heated. Hearth plates must withstand high temperatures without sagging or scaling. They are often made of a special nickel-chromium, heat-resistant alloy. If the furnace is designed for the heat treatment of high-speed steels, the hearth plate may be made of a carbon and silicon. Grids, usually made of iron-chromium-nickel alloy, keep heavy or long sections of material off the hearth plate. The use of grids ensures more uniform heating of the material and tends to prevent warping. A grid for an electric furnace is shown in figure 15-8. A special type of electric furnace known as an AIR-CIRCULATING FURNACE is sometimes used for stress-relieving and tempering. Air-circulating furnaces are relatively low-temperature units, usually designed to operate at temperatures ranging from 275° to 1,250°F. Temperature control is both accurate and rapid. The maximum temperature variation is seldom more than plus or minus 5°F, and very rapid changes to a higher or lower temperature are possible. Temperature Measurement and Control The measurement and control of temperature are extremely important in all heat-treating processes. Modern heat-treating furnaces are equipped with various devices for indicating (and in some cases recording) temperatures. Most furnaces are also equipped with temperature controllers. The most commonly used device for measuring the temperature in a heat-treating furnace is the THERMOELECTRIC PYROMETER. This instrument (fig. 15-9) consists of a thermocouple, an extension lead, and an indicating unit. The indicating unit is calibrated in degrees Fahrenheit or Centigrade. Some pyrometers merely indicate the temperature; others indicate it and record it. Most electric furnaces are equipped with pyrometers that are controllers as 15-8 Figure 15-9.—Thermoelectric pyrometer used in heat-treating furnance. well as measuring devices. This type of instrument can be set to develop and maintain any desired temperature within the limits of the furnace design. If you are using improvised heat-treating equipment, you will probably not have any accurate way of measuring temperature and will have to improvise methods for determining temperature. It is possible to estimate the temperature of ferrous metals by noting the color changes that occur when the material is heated. This method is not practical for nonferrous metals since most nonferrous metals melt before they show a color change. At best, the color method of judging temperatures is guesswork. Nonetheless, you should develop some skill in using this technique. It may be the only method you have to estimate temperature when you do not have adequate heat-treating equipment. The best way to learn to judge the temperature of ferrous metal by color is by heating small samples of clean, polished steel under controlled conditions. This way you can check the color of the sample against the actual temperature. Also, study the color charts that relate color and temperature. Your perception of the colors will be affected by the color and intensity of the light in the furnace or in the room where you are working. Use standard lighting conditions, if possible, when you must estimate the temperature of a metal by observing the color. Charts are available in various handbooks and textbooks on metals. Table 15-1 is a rough guide to the color-temperature relationships of steel. At temperatures below those given in table 15-l) another type of color determination can be made. If steel is thoroughly cleaned and polished, the surface will appear to change color as the material is heated. An oxide film forms on the polished surface as the steel is heated, and the oxide color corresponds to a certain temperature. Some oxide colors for steel are given in table 15-2.
Table 15-1.—Relationship Between Color and Temperature of Steel Color Faint red, visible in darkness ............. Faint red, visible in daylight .............. Blood red. ....................... Dark cherry ...................... Medium red ...................... Cherry or full red ................... Bright red ....................... Salmon ......................... Grange ......................... Lemon ......................... Light yellow ...................... White. ......................... Dazzling white ..................... Table 15-2.—Oxide Colors for Steel of Various Temperatures Color Pale yellow. ...................... Straw .......................... Golden yellow ..................... Brown ......................... Brown dappled with purple .............. Purple ......................... Dark blue ........................ Bright blue ....................... Pale blue ........................ 15-9 Approximate Temperature (°F) 750 900 1050 1075 1250 1375 1550 1650 1725 1825 1975 2200 2350 Approximate Temperature (°F) 428 446 469 491 509 531 550 567 610
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Naval Education and Training Comman
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MACHINERY REPAIRMAN NAVEDTRA 12204-
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PREFACE This Training Manual (TRAMA
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CONTENTS CHAPTER PAGE 1. 2. 3. 4. 5
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Another job description found in pr
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1-2, and 1-3 show some of the commo
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You must know the location of tools
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The correct way to measure an insid
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appropriate sides of the jaws on th
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Dial Bore Gauge The dial bore gauge
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Gear Tooth Vernier Use a gear tooth
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Surface Gauge A surface gauge (fig.
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Figure 1-20.—Center gauge. angle
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accuracy. They generally come in ma
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MICROMETERS is essentially the same
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meanings of these terms and the imp
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number is shown for roughness heigh
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Figure 2-7.—Master roughness scal
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Figure 2-11.—Checking surface fin
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Figure 2-17.—Laying out a 45-degr
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Figure 2-24.—Setting and using a
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Figure 2-29.—Bisecting an angle.
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prick-punch “witness marks” aro
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Figure 2-35.—Filing. The crosshat
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keyway broach requires a bushing th
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The steps involved in repairing a d
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SETTING UP OXYACETYLENE EQUIPMENT T
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GREASE IN THE PRESENCE OF OXYGEN UN
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Strength metal into thin sheets. Le
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and forming into plates, billets, b
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Each of the aluminum alloys has pro
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with an average carbon content of 1
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The manufacturer is required to mak
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with that of known specimens. Many
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Gray cast iron produces a spark str
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Table 3-4.—Major Groups of Plasti
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Lathe Operations Lathe operations a
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mechanism is also attached to the s
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Band Selection and Installation The
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File Bands A file band consists of
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This prevents sagging of the file b
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Figure 4-16.—Butt welder-grinder
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paragraphs contain the procedures f
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Figure 4-22.—Disk-cutting attachm
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Figure 4-26.—Sensitive drill pres
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shops are the Morse taper shank, sh
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Figure 4-30.—Common types of clam
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Figure 4-34.—Two types of counter
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andomly follow the straight sides a
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CHAPTER 5 OFFHAND GRINDING OF TOOLS
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Figure 5-4.—Standard marking syst
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DIAMOND WHEELS Diamond grinding whe
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WHEEL CARE AND STORAGE It’s easy
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allows cutting speeds approximately
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Figure 5-13.—Surface finish vs no
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Figure 5-17.—Boring bars for carb
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Figure 5-19.—Chip breakers. a rad
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Internal-threading tool: The intern
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Downcutting tool: You may grind and
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Figure 5-32.—Grinding drill lip c
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Figure 5-37.—Grinding a twist dri
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ways in alignment with the headstoc
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Figure 6-4 shows this plate for the
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Before you insert a center or tooli
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FEED ROD The feed rod transmits pow
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lower lever has eight positions, ea
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Figure 6-14.—Quick-change toolpos
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Figure 6-21.—Three-jaw universal
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Figure 6-26.—Cutaway showing the
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Figure 6-32.—Thread dial indicato
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TRACING ATTACHMENTS A tracing attac
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2. Place the level across the bed a
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Figure 6-41.—Aligning lathe cente
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Figure 6-45.—Boring center hole.
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ends of the mandrel when you press
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Figure 6-52.—Centering work with
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Figure 6-56.—Work mounted on a ca
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FEED is the amount the tool advance
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Rough Turning Figure 6-62.—Rough
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Square, round, and “V” grooves
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Figure 6-69.—Knurled impressions.
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machined surfaces that could become
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produced by the same amount of seto
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cross-feed screw and the cross-slid
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When special threads are required b
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Figure 6-83.—Acme thread and form
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where An example of a pipe thread i
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The wire size you should use to mea
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Using the Thread-Cutting Stop Becau
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Figure 6-96.—Finishing the end of
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shown in figure 6-101. Two slots ar
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Figure 7-1.—Universal milling mac
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A. Spindle G. Spindle speed selecto
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with a split clamp to the overarm a
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to the table of the milling machine
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that most index heads have a 40 to
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Rapid indexing is used when a large
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or one complete turn plus 36 holes
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allows you to index divisions from
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from the one in which the pin is in
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Figure 7-24.—Side milling cutter.
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A. B. C. D. E. Figure 7-32.—Doubl
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Figure 7-36.—Inserted tooth face
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Figure 7-43.—Sprocket wheel cutte
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Figure 7-48.—Stub arbor. or on th
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Figure 7-54.—Spring collet chuck
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Figure 7-56.—Face milling. FACE M
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11. 12. 13. 14. 15. 16. 17. 18. 19.
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A. Lock screw for dog D. End mill B
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8. 9. 10. 11. 12. 13. 14. 15. 16. 1
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11. 12. 13. 14. 15. 16. 17. 18. 19.
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Figure 7-71.—Visual alignment of
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machine table. You will hold the cu
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Figure 7-77.—Boring with a fly cu
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Figure 7-79.—Vertical milling att
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Table 7-2.—Surface Cutting Speeds
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Table 7-4 shows recommended chip lo
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Figure 8-2.—A 36-inch vertical tu
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28.194 Figure 8-3.—Refacing a val
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HORIZONTAL BORING MILL The horizont
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7. After you have tightened the mou
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The table can be power driven to pr
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CHAPTER 9 SHAPERS, PLANERS, AND ENG
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Figure 9-3.—Swiveled and tilted t
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extent in planer and shaper work To
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the cutting speeds and related mach
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Figure 9-10.—Internal keyway: A.
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7. 8. 9. 10. 11. 12. 13. 14. Replac
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or housing attached on one side of
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Figure 9-18.—Engraving machine. F
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CUTTER SPEEDS The speeds listed in
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can readily see it after grinding t
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Figure 9-29.—Using an indexing at
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Any further movement of the work wi
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Figure 10-1.—Grain depth of cut;
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To select the proper work speed, ta
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Figure 10-8.—Magnetic chuck used
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can do on a surface grinder. Use th
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for straight cylindrical grinding o
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Figure 10-15.—Typical tooth rest
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of the work. Raise or lower the whe
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Figure 10-23.—Staggered-tooth sid
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Figure 10-28.—Grinding the periph
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Once the teeth are uniform, they sh
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After you have honed out the inaccu
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MACHINES With the rapid development
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Figure 11-3.—Slant bed for CNC la
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Figure 11-6.—A typical CNC contro
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Figure 11-8.—Continuous-path angl
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CHAPTER 12 METAL BUILDUP CHAPTER LE
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Figure 12-1.—Typical installation
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Figure 12-5.—A typical sandblaste
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Clean, dry air is essential for pro
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It can reduce the amount of masking
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quality assurance function of the p
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pass-fail. In our educational syste
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straighten a shaft, however, always
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Figure 13-4.—Lapping tools. has t
Page 322 and 323: pipe in which the valve is installe
Page 324 and 325: Figure 13-10.—Constant-pressure g
Page 326 and 327: When you install the control valve
Page 328 and 329: casing wearing rings, impeller wear
Page 330 and 331: Figure 13-17.—Removing a broken b
Page 332 and 333: Figure 13-23.—Metal disintegrator
Page 334 and 335: Figure 13-25.—Portable boring bar
Page 336 and 337: Figure 14-1.—Cutting specially sh
Page 338 and 339: For example, use the following proc
Page 340 and 341: at an angle to each other, as long
Page 342 and 343: Figure 14-6.—Development of evenl
Page 344 and 345: Table 14-1.—"K" Factor Table Tabl
Page 346 and 347: Figure 14-11.—Standard universal
Page 348 and 349: 6. Find the NPD. 7. Find the 8. Fin
Page 350 and 351: FA - Face angle OD - Outside diamet
Page 352 and 353: 7. Pitch diameter (PD)—This is th
Page 354 and 355: SELECTING A BEVEL GEAR CUTTER To cu
Page 356 and 357: Figure 14-20.—Profiling a bevel g
Page 358 and 359: . Use the following formulas to sol
Page 360 and 361: Figure 14-25.—Milling machine set
Page 362 and 363: 9. Diametral pitch (DP) METHOD OF M
Page 364 and 365: explains the classes and the manufa
Page 366 and 367: GRAINS (irregularly shaped crystals
Page 368 and 369: Figure 15-2.—Microscopic structur
Page 370 and 371: Figure 15-5.—Typical structure of
Page 374 and 375: Table 15-3.—Average Cooling Rates
Page 376 and 377: cases. A wide variety of quenching
Page 378 and 379: These various temperature arrests o
Page 380 and 381: known as pearlite, and the A1 tempe
Page 382 and 383: quickly cooled to and held at a som
Page 384 and 385: Available information indicates tha
Page 386 and 387: slowly from the tempering temperatu
Page 388 and 389: Table 15-4.—Heat-Treating Tempera
Page 390 and 391: Figure 15-20.—Design of a cam. A.
Page 392 and 393: In carburized steel, spalling is ca
Page 394 and 395: used to make positive identificatio
Page 396 and 397: HONING—Finishing machine operatio
Page 398 and 399: Table AII-2.—Decimal Equivalents
Page 400 and 401: Table AII-4.—Formulas for Dimensi
Page 402 and 403: Table AII-5.—Number, Letter and F
Page 404 and 405: Table AII-7.—Screw Thread and Tap
Page 406 and 407: Table AII-9.—3-Wire Method of Mea
Page 408 and 409: Table AII-11.—Circles Circumferen
Page 410 and 411: Table AII-13.—Taper Per Foot and
Page 412 and 413: p 1 I vi 2 P F \ = = a AII-16
Page 414 and 415: Table AII-16.—Drill Sizes for Tap
Page 416 and 417: Having Circular pitch Circular pitc
Page 419 and 420: APPENDIX IV DERIVATION OF FORMULAS
Page 421: (1) NT is the connecting link betwe
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Walker, John R., Machining Fundamen
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A Adjustable gauges, 1-7 adjustable
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Engine lathes, 6-1 attachments and
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Layout methods, 2-8 M forming angul
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Stub tooth gears, 14-27 American st
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