Machinery Repairman

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straighten a shaft, however, always be sure the leading petty officer of the shop is informed of the operation. Use the following steps to straighten a shaft: 1. Mount the shaft between centers in a lathe. If the shaft is too long, mount it on rollers. 2. Clamp a dial indicator on the compound rest, locate the area of the bend, and measure how much the shaft is bent (runout). To determine the area of the bend, run the dial indicator along the shaft longitudinally. The greatest variation of the pointer from zero indicates the bend area. With the dial indicator set at this point, rotate the shaft and note the amount of fluctuation of the pointer. This fluctuation is the amount of runout. Mark the longitudinal position of the bend and the high side of the bend with chalk or a grease pencil. 3. Remove the shaft from the lathe and place it on a hydraulic press. Place a V-block on each side of the bend area and turn the shaft so the high side is up. Move the press ram downward until it touches the shaft. Set up a dial indicator so that the contact point contacts the high side of the shaft as near to the ram as possible. 4. Carefully apply pressure on the shaft with the ram. Watch the pointer of the dial indicator to determine how much the shaft is “sprung” in the direction opposite the bend. When the indicator reading is 0.002 or 0.003 inch greater than the amount of runout, release the ram pressure. 5. Set up the shaft between centers and check again as expiained in step 1. Repeat steps 2, 3, and 4 until the runout is decreased to within acceptable limits. If the first attempt produces little or no change in runout, spring the shaft further in the second operation to overcome the elasticity of the shaft so that it bends in the required direction. It’s better to make several tries and gain a few thousandths of an inch at a time than to do it in one or two tries and perhaps bend the shaft too fur in the opposite direction. Stubbing a Shaft You can repair the damaged ends of shafts by removing the bad section and replacing it with a new “stub” end. Always check to see if your type commander allows stubbing of shafts. Use the following steps to stub a shaft: 1. If a blueprint is not available, make a drawing of the shaft showing all dimensions. 2. Begin with a piece of scrap stock (spud) of the same material as the shaft. Use a lathe to machine it to 13-4 the diameter of the shaft at the point where the center rest will be used. Carefully align the center rest on this spud. 3. Mount the undamaged end of the shaft in a 4-jaw chuck and “zero in” the shaft near the jaws of the chuck Use soft jaws or aluminum shims to prevent damage to the shaft surface. 4. Position the previously set center rest under the shaft so the center rest is between the chuck and the damaged end of the shaft. 5. Cut off the damaged portion of the shaft. 6. Face, center drill, and drill the end of the shaft. The diameter of the hole should be about 5/8 of the diameter of the shaft; the depth of the hole should be at least 1/2 times the hole diameter. 7. Chamfer the end of the shaft liberally to allow space for weld deposits. 8. Make a stub of the same material as the shaft. The stub should be 1/4 inch larger in diameter and 3/8 inch longer than the damaged portion of the shaft plus the depth of the hole drilled in the shaft. This provides ample machining allowance. 9. Machine one end of the stub to a press fit diameter of the hole in the shaft. The length of this portion should be slightly less than the depth of the hole in the shaft. (A screw fit between the shaft and stub can be used instead of the press lit.) 10. Chamfer the shoulder of the machined end of the stub the same amount as the shaft is chamfered. 11. Press (or screw for a threaded fitting) the stub into the shaft and have the chamfered joint welded and stress relieved. 12. Mount the shaft with the welded stub back in the lathe, and machine the stub to the original shaft dimensions provided by the drawing or blueprint. REPAIRING VALVES To repair valves, you must have a knowledge of the materials from which they are made. Each material has its limitations of pressure and temperature; therefore, the materials used in each type of valve depend upon the temperatures and pressures of the fluids that they control. Valves are usually made of bronze, brass, cast or malleable iron, or steel. Steel valves are either cast or forged and are made of either plain steel or alloy steel.
Alloy steel valves are used in high-pressure, high-temperature systems; the disks and seats of these valves are usually surfaced with a chromium-cobalt alloy known as Stellite. This material is extremely hard. You will find information on the commonly used types of valves and their construction in Fireman, NAVEDTRA 12001. The information in the following sections applies to globe, ball, and gate valves, but the procedures can usually be adapted to repair any type of valve. Repairing Globe Valves Begin with an inspection of all parts of the valve for wear and alignment and, if you find them defective, repair or renew them. However, most valve repair is limited to overhaul of the seat and disk, and we will concentrate on those procedures. Make a close inspection of the valve seat and disk. Look for erosion, cuts on the seating area, and proper fit of the disk to its seat. In a normal overhaul, you will grind-in the seat and disk, or lap the seat and machine the disk in a lathe. When the parts are in such bad condition that the normal procedure will not work, you must machine both the valve disk and valve seat in a lathe. If the disk and seat appear to be in good condition, use the spotting-in procedure described in the next paragraphs to be sure. SPOTTING-IN.—Use this procedure to visually determine whether or not the seat or disk make good contact with each other. To spot-in a valve seat, first apply a thin coating of prussian blue evenly over the entire machined face surface of the disk. Next, insert the disk into the valve and rotate it a quarter turn, using a light downward force. The prussian blue will adhere to the valve seat at points where the disk makes contact. Figure 13-3 shows the patterns of prussian blue on a correct seat and on imperfect seats. After you have noted the condition of the seat surface, wipe all the prussian blue off of the disk face surface, then apply a thin, even coat on the contact face of the seat. Again place the disk on the valve seat and rotate the disk a quarter turn. Examine the resulting blue ring on the valve disk. If the ring is unbroken and of uniform width, and there are no cuts, scars, or irregularities on the face, the disk is in good condition. If the ring is broken or wavy, the disk is not making proper contact with the seat and must be machined. GRINDING.—Valve grinding is the method of removing small irregularities from the contact surfaces 13-5 Figure 13-3.—Examples of spotted-in valve seats. of the seat and disk. You also will use this process to on seats or disks you have machined. To grind-in a valve, apply a small amount of grinding compound to the face of the disk, insert the disk into the valve and rotate the disk back and forth about a quarter turn. Shift the disk-seat relation from time to time so the disk will be rotated gradually in increments through several rotations. The grinding compound will gradually be displaced from between the seat and disk surfaces, so you must stop every minute or so to replenish the compound. For best results when you replenish, wipe the old compound off the seat and the disk before you apply the new compound. When it appears that the irregularities have been removed, spot-in the disk to the seat as described previously. When you first spot-in a machined valve seat and disk, the scat contact will be very narrow and located close to the edge of the bore. Grinding-in, using finer compounds as the work progresses, causes the seat contact to become broader until it looks like the “correct seat” shown in figure 13-3. The contact area should be a perfect ring, covering approximately one-third of the seating surface. Avoid over-grinding. It will produce a groove in the seating surface of the disk and it may round off the straight angular surface of the seat. You will have to machine the surfaces to correct the effects of overgrinding. LAPPING.—Lapping serves the same purpose as grinding, but it works only on the valve seat and it removes slightly larger irregularities than grinding. In this procedure, you will use a cast-iron lapping tool that
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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
Page 267 and 268: can readily see it after grinding t
Page 269 and 270: Figure 9-29.—Using an indexing at
Page 271: Any further movement of the work wi
Page 274 and 275: Figure 10-1.—Grain depth of cut;
Page 276 and 277: To select the proper work speed, ta
Page 278 and 279: Figure 10-8.—Magnetic chuck used
Page 280 and 281: can do on a surface grinder. Use th
Page 282 and 283: for straight cylindrical grinding o
Page 284 and 285: Figure 10-15.—Typical tooth rest
Page 286 and 287: of the work. Raise or lower the whe
Page 288 and 289: Figure 10-23.—Staggered-tooth sid
Page 290 and 291: Figure 10-28.—Grinding the periph
Page 292 and 293: Once the teeth are uniform, they sh
Page 294 and 295: After you have honed out the inaccu
Page 296 and 297: MACHINES With the rapid development
Page 298 and 299: Figure 11-3.—Slant bed for CNC la
Page 300 and 301: 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 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 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
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Figure 15-2.—Microscopic structur
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Figure 15-5.—Typical structure of
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Figure 15-8.—Grid for heat-treati
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Table 15-3.—Average Cooling Rates
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cases. A wide variety of quenching
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These various temperature arrests o
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known as pearlite, and the A1 tempe
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quickly cooled to and held at a som
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Available information indicates tha
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slowly from the tempering temperatu
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Table 15-4.—Heat-Treating Tempera
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Figure 15-20.—Design of a cam. A.
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In carburized steel, spalling is ca
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used to make positive identificatio
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HONING—Finishing machine operatio
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Table AII-2.—Decimal Equivalents
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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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