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7. Pitch diameter (PD)—This is the diameter of the gear blank one addendum down at the large end of the gear. 8. Outside diameter (OD) a. This is the maximum diameter of the gear. b. The gear blank is machined to this outside diameter. c. The outside diameter is obtained by adding the pitch diameter and twice the angular addendum. 9. Angular addendum (ANG ADD) a. b. C. This is one-half the difference between the pitch diameter and the outside diameter. In the triangle shown in figure 14-16, view C, the hypotenuse is the addendum and the side adjacent to the angle (BCA) is known as the angular addendum. To obtain the angular addendum (ANG ADD), simply multiply the addendum of the gear by the cosine of angle BCA. ANG ADD = ADD × COS 10. Tooth dimensions (TD) a. All tooth dimensions at the large end are the same as a spur gear of the same DP. b. All tooth dimensions at the small end are a percentage of the large end, depending of the face width ratio. 11. Face width (FW) (fig. 14-15) a. This is the length of the tooth. b. The gear blank is machined to this dimension. 12. Pitch cone radius (PCR) a. b. c. This is the length of the side of a cone formed by the bevel gear. This radius is used extensively in calculations. In the triangle shown in figure 14-16, view D, the hypotenuse is the pitch cone radius and the side opposite the pitch cone angle is equal to one-half the pitch diameter (0.5 PD). 14-18 d. By using our knowledge of trigonometry, we can obtain the PCR by using the cosec of and one-half the pitch diameter. PCR = cosec × 0.5PD. 13. Pitch cone radius small (PCR s). This is the difference between the pitch cone radius and the face width. PCR s = PCR - FW. 14. Face width ratio (FWR) a. This is the ratio of the pitch cone radius and the face width. FWR = b. The small tooth dimensions are calculated from this ratio. 15. Proportional tooth factor (PTF). This is the ratio between the pitch cone radius small and the pitch cone radius. FTF 16. Small tooth dimensions. Multiply any large tooth dimension by the proportional tooth faction to find the dimension of the small tooth of the gear or pinion. 17. Number of teeth for cutter selection (NTCS) a. b. c. d. e. In the triangle shown in figure 14-16, view E, the NTCS is the hypotenuse and the side adjacent is the number of teeth of the gear. The known angle in this case is the pitch cone angle, or the back cone angle. To obtain the NTCS, simply multiply the secant of by the NT. NTCS = NT × Sec The NTCS is taken from the number of teeth on an imaginary spur gear that has a different pitch diameter (PD) than the pitch diameter (PD) of a bevel gear. When your computation for the NTCS contains a decimal number, round the computation to the next higher whole number.
Figure 14-17.—Formulas for calculating chordal thickness. Chordal Addendum and Chordal Thickness Before you can measure a manufactured gear tooth accurately, you must know the chordal addendum and the chordal thickness. These dimensions are used to measure the size of the gear tooth. Chordal addendum (corrected addendum) a c. This is the distance from the top of a gear tooth to the chord across the gear tooth at the pitch circle (fig. 14-17, view A). It is the point at which the chordal thickness is measured. Chordal thickness of a gear tooth (t c). This is the distance in a straight line (chord) from one side of the tooth to the other side at the points where the pitch circle passes through the gear tooth (fig. 14-17, view A). Use the following methods to calculate the chordal addendum and the chordal thickness: You can calculate the dimensions by using the formulas shown in figure 14-17, view B. However, you can also use tables such as table 14-3, part B, to make 14-19 bevel gear calculations. Simply substitute the constant into the following formula: B. NOTE: Obtain the constant from table 14-3, part The procedure used to solve the chordal thickness of the large tooth of a bevel gear is the same as that for a spur gear. To determine the chordal addendum (corrected addendum) a c small and the chordal thickness of the small tooth, multiply the value of the large tooth by the proportional tooth factor (PTF). Backlash Allowance of a Bevel Gear You learned earlier that backlash is the amount by which the width of a gear tooth space, when two gears are meshed together, exceeds the thickness of the engaging tooth on the pitch circles. You must take these measurements with a device used for that purpose. Theoretically, when gear teeth are meshed, they should run with little backlash. However, manufacturing tolerances make this impossible. There must be space between the gear teeth for lubrication and for expansion due to temperature changes at high speeds. Just as with helical gears, bevel gears must have enough freedom between teeth so they will not bind when the gears turn. Table 14-3, part B shows the recommended backlash allowance corresponding to the gear’s diametral pitch (DP). To determine the chordal thickness with backlash at the large end of the tooth, use the following formula: Chordal thickness = B. NOTE: Obtain the constant from table 14-3, part To determine the corrected working depth (WD) with backlash at the large end of the tooth, use the following formula:
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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
Page 302 and 303: Figure 11-8.—Continuous-path angl
Page 304 and 305: CHAPTER 12 METAL BUILDUP CHAPTER LE
Page 306 and 307: Figure 12-1.—Typical installation
Page 308 and 309: Figure 12-5.—A typical sandblaste
Page 310 and 311: Clean, dry air is essential for pro
Page 312 and 313: It can reduce the amount of masking
Page 314 and 315: quality assurance function of the p
Page 316 and 317: pass-fail. In our educational syste
Page 318 and 319: straighten a shaft, however, always
Page 320 and 321: 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 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 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
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Table AII-5.—Number, Letter and F
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Table AII-7.—Screw Thread and Tap
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Table AII-9.—3-Wire Method of Mea
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Table AII-11.—Circles Circumferen
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Table AII-13.—Taper Per Foot and
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p 1 I vi 2 P F \ = = a AII-16
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Table AII-16.—Drill Sizes for Tap
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Having Circular pitch Circular pitc
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APPENDIX IV DERIVATION OF FORMULAS
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(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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