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cases. A wide variety of quenching oils may be used, including animal oils, fish oils, vegetable oils, and mineral oils. Oils have a slower cooling rate than brine or water but a faster cooling rate than air or solid materials. Quenching oils are usually used in the temperature range of 120° to 150°F. The chief danger involved in quenching with oil is that a hot metal piece may raise the temperature of the oil to the flash point and cause it to burst into flames. A cover should always be kept near a quenching tank that is used for oil. If the oil flashes into flames, put the cover over the tank immediately to smother the fire. Some water usually collects in the bottom of the oil tank. The water does no harm if only a small amount is present. If enough water is present that the work extends into the water, the rapid quenching action of the water may cause the piece to crack CAUSTIC SODA in water is used for some steels that require rapid quenching. A lo-percent caustic soda solution quenches faster than water, but slower than brine. Nonferrous metals are not quenched in caustic soda solutions. Figure 15-11.—Iron-carbon phase diagram. 15-12 AIR is used for cooling some high-alloy steels and some nonferrous metals. Both still air and circulating air are used. For either method the work pieces are placed on racks or other suitable containers so all parts are uniformly exposed. Air is often circulated by electric fans arranged to provide uniform cooling. Compressed air is sometimes used to concentrate the cooling on particular areas. Compressed air used for this purpose must be entirely free of moisture. Any moisture in the air produces rapid quenching wherever it touches the metal and may cause cracking or hard spots. MOLTEN LEAD at temperatures ranging from 650° to 1,100°F is often used as a first-stage quench for high-speed steels. A common practice is to quench high-speed steel in molten lead as soon as the work is removed from the furnace and to follow this quench by cooling the part in still air to about 200°F before tempering. Molten lead is not used as a quenching medium for nonferrous metals. MOLTEN SALT at temperatures ranging from 300° to 1,000°F is sometimes used as a quenching medium
Figure 15-12.—Idealized cooling curve for pure iron. for steels that tend to crack or distort from more sudden quenches. The final cooling for the temperature of the molten salt bath is accomplished in still air. All traces of the salt must be washed from the steel to prevent corrosion. SPECIAL PROTECTIVE ATMOSPHERES are used for the first-stage cooling of some steels. The protective atmosphere almost entirely eliminates air from around the metal and thus prevents scaling. When the steel has cooled enough so there is no further danger of scaling, the remainder of the cooling is done in still air. PRINCIPLES OF HEAT-TREATING FERROUS ALLOYS As we have seen, the properties of a metal or an alloy are directly related to the metallurgical structure of the material. Since we know that the basic purpose of heat treatment is to CHANGE the properties of the materials, let’s see how this is done. The following sections deal with basic considerations in heat treat-ment—equilibrium diagrams, transformation temperatures, and the effects of heating, holding at temperature, and cooling. EQUILIBRIUM DIAGRAMS The relationships among the various metallurgical structures that compose alloys and the temperatures at which these structures exist are shown on existing equilibrium diagrams for all major alloy systems. Figure 15-11 shows a simplified equilibrium diagram (also called a phase diagram) for iron-carbon alloys. This type of diagram gives a good overall view of the effects of temperature on the structures of various 15-13 alloys. However, you should note that an equilibrium diagram indicates equilibrium conditions-you might say, ideal conditions of very slow and very uniform heating and cooling. The rate and uniformity of heating and cooling affect the internal structure of alloys and alter the relationship between temperature and internal structure. Therefore, equilibrium diagrams represent theoretical rather than actual conditions. TRANSFORMATION TEMPERATURES If you allow a molten sample of pure iron to cool slowly and measure the temperature of the iron at regular intervals, an idealized (equilibrium) timetemperature plot of the data will appear as shown in figure 15-12. The horizontal d&continuities (temperature arrests) in this curve are caused by physical changes in the iron. The first arrest at 2,800°F marks the temperature at which the iron freezes. The other arrests (known as transformation temperatures or critical points) mark temperatures at which certain internal changes take place in the solid iron. Some of these temperatures are very important in the heat treatment of steel. As was mentioned before, the atoms in all solid metals are arranged in a definite geometric pattern. The atoms in iron immediately after freezing are arranged in the body-centered cubic structure. In this crystal structure the unit cell consists of a cube with an iron atom at each of the eight comers and another in the center. Each of the many individual grains (crystals) of which the solid metal is composed is built up of a very large number of these unit cells, all oriented alike in the same grain. This high-temperature iron is known as delta iron. At 2,550°F (the A 4 point, fig. 15-12), iron undergoes an allotropic transformation; that is, the arrangement of the atoms in the crystal changes. The new crystal structure is face-centered cubic, and the unit cell again consists of a cube with an iron atom at each of the eight corners, but with an iron atom in the center of each of the six faces instead on one in the center of the cube. This form is known as gamma iron. At 1,670°F (the A 3 point), iron undergoes another allotropic transformation and reverts to the body-centered cubic system. This structure, which is basically the same as the structure of delta iron, is stable at all temperatures below the A 3 point and is known as alpha iron. The arrest at 1,420°F (the A 2 point) is not caused by an allotropic change. It marks the temperature at which iron becomes ferromagnetic and is, therefore, termed the magnetic transition. Above this temperature iron is nonmagnetic.
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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
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pipe in which the valve is installe
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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 372 and 373: Figure 15-8.—Grid for heat-treati
Page 374 and 375: Table 15-3.—Average Cooling Rates
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
Page 424 and 425: 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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