Document zzRdOXb9qO2G0gNK8aNRBrNK7

Hot Working of Metals cuit so that the motor cannot be started when the props are in use All die clamps, bolts, washers, blocking, wrenches, and handling equipment should be m good condition at all times The table wedges which are used for mak ing vertical adjustment of the dies must be kept free of scale so that the wedge can be raised and lowered with minimum pressure Trucks or driving rams should not be used for this operation If wedges are kept free of scale, they can be raised or lowered by hand or by air motor wrench Maintenance Maintenance of forging presses requires the same precautions used in maintenance work on power presses used in cold stamping The operating power source should be locked out so that the equipment cannot be energized while it is being worked on If adjustments have to be made while the press is energized, the work must be earned out under the direct supervision of the maintenance supervisor Suitable permanent work platforms should be installed for making brake adjustments and doing repair work at the surge tank and booster cylinders To prevent falls, mainte nance men should not use portable straight ladders nor stand on parts of the press, such as the press crown or the backshaft Major repair work on forging presses usually requires removal of bulky, heavy parts Tear ing down of the rolling type clutch, flywheel, ram, pitman, and crankshaft requires special heavy-duty rigging used by skilled workmen trained in this type of work The brake should be adjusted properly and kept in good repair Precautions must be taken to prevent the brake lining from be coming flooded with oil A sheet steel disk about 2 in larger than the brake wheel, placed on the eccentric shaft back of the brake wheel, will help reduce the amount of lubricant on the brake Pitman bolts should be securely tightened It may be necessary to design and make a socket or box end wrench with a strong heavy handle for the specific press Flywheel hubs, clutch spline hubs, pinion gears, and brake wheels should not be per mitted to become loose on the pinion shaft If they do become loose and run that way very long, keys and keyways will be ruined and the keys will break out a portion of the pinion shaft on one side of the keyway The keys on each side of the pinion shaft should be inspected periodically and driven tight if they are loose When a key will no longer stay tight, it should be replaced with a carefully fitted new key When the hub or gear on the shaft becomes too loose, it wiil be impossible to hold the keys tight and the shaft will have to be turned down The inside of a steel hub should be welded and bored to a shrink fit on the new shaft size The keyways should be remachmed and new keys made If the hub is cast iron, a tapered sleeve can be made or a new hub fitted to the shaft Expenenced repairmen warn against weld ing the flywheel end of the pinion shaft If normalizing of the welded section is not com plete, a crack may start and allow the shaft to break and drop the rotating flywheel Crank shafts and backshafts on forging presses like wise should not be welded The friction slip on a press should be tight ened so that it will not creep even on heavy jobs If the friction slip is allowed to move a small amount with every forging, this move ment will polish or glaze the friction surfaces and soon the friction slip will move more with each forging This movement will cause the friction surface to score the hub and clamp surfaces Rotation of the flywheel on the friction hub will frequently wear or cut the inside diam eter of the flywheel so that it runs off center To correct this condition, the inside diameter of the flywheel can be bored and fitted with a bronze bushing Sometimes the eccentric shaft becomes cracked in the fillet on each side of the ec centric This defect is usually noticed when the shaft is taken out so that the mam bearings can be checked or the shaft can be machined This crack should be examined carefully to determine its length, depth, and direction of travel If the crack is in a critical area where failure would permit the rolling dutch to drop oft, then the shaft must be replaced Other Forging Equipment Hot trimming dies can be made from hard ened chrome, nickel, carbon and vanadium steels or from medium carbon steels with 848