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NMWR-9-2815-220 Overhaul Manual for M60 M88 Engine AVDS-1790-2CA, AVDS-1790-2DA, AVDS-1790-2DR Download

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NMWR 9-2815-220 CRANKCASE ASSEMBLY OVERHAUL—Continued 0006 00 RECLAMATION – Continued (f) Apply a metalspray coating with the 6P Themospray gun using parameters packed with the material, giving special attention to the spray distance and maintaining the spray angle as close to 90° to the substrate surface as practical. Do not allow the part temperature to exceed 300° F (149° C). Interrupt spraying as required. (1) When spraying main bearing fit area use Metco 445 Self-Bonding Aluminum Bronze Composite Powder adhering to MIL-STD-1687A(1). Allow extra 0.010 – 0.050 in. (0.254 – 1.27 mm) coating thickness for finishing. (2) When spraying side mating surfaces use Metco 447 Self-Bonding Molybedenum-Nickel-Aluminum Composite Powder (adhering to MIL-STD-1687A(1)). Allow extra 0.10 (0.254 mm) inch coating thickness for finishing. (g) Seal Metco 445 coating while hot, to improve machining, using Metco 185 Sealer. (h) Finishing. (1) Main bearing fit area (Metco 445). If block and cap are machined together, machining is done dry using feeds and speeds normally used for cast iron. If caps are machined individually, a milling machine is used. Use a 883 grade carboly tool bit or equivalent square tool with 1/32 in. (0.7620 mm) radius set at 45 degree angle to part. Keep tool sharp and machine at the following parameters: Surface work speed 600 ft./min. Traverse speed 0.002 – 0.004 in. per revolution Infeed 0.010 in. per side, rough cut 0.005 in. per side, finish cut (2) Side mating surfaces (Metco 447). Grind using a surface grinder with 46J or 46K silicon carbide wheel or hand file. Do not load wheel when roughing. Leave 0.002 – 0.003 in. (0.0508 – 0.0762 mm) after roughing for final grind. Dress wheel before grinding to finish size. NOTE Quality control will inspect finished part to insure adherence to this procedure. (i) All mounting surfaces repaired by this process shall be 100% inspected for coating integrity after machining. The coating shall show no bond separation at the coating to base metal interface. The coating shall be free from blistering, cracking, chipping, and frayed edges. There shall be no bleedout of oil or other contaminants through the finished coating. 2. Crankshaft main bearing saddle areas can be reclaimed by metalspraying according to the procedures outlined on next page. Refer to OIP 11684087 (Table 3). 0006 00-6 Change 1