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June, 1919 THE MARINE REVIEW 2/7 These are molded in heavy flasks which are accurately machined and fastened together with two guide pins, cne at each end. The holes for these are drilled by means of a template to insure accuracy. The large square core which forms the crank pit is made on a plate to facilitate handling, finishing and setting. The greater portion of this casting is molded in the drag. It is molded bottom: up with the curved portion in the cope. Molds for the columns are made in two flasks. The mold is poured from the bottom in order that any slight amount of dirt may be caught under the core and thus prevented from reaching the upper edge of the casting. All marine engine castings must be sound as they have to pass close inspection before machining. While great: care is exercised to see that none but sound castings are delivered to the machine shop, greater care must be used in conducting the various machining operations as other- wise castings that represent a _ con- siderable outlay in time and material might be rendered valueless. The bed sections as they come from the foundry are first roughed cut all over on a planer, after which the ends that are to be bolted to- gether to unite the three castings into a complete bed are carefully planed by facing with the down feed. The sections are then drilled for bolt and dowel holes and firmly fastened to- gether. The object of the dowel pins is to facilitate accurate resetting in case it should be necessary to disas- semble the unit at some future time. After joining together, the bed is again taken to the planer where a finishing chip is taken over the top and the bottom of the casting. A coarse feed in connection with a goose-neck finishing tool is used for this operation. The object FIG. 8--BORING THE SEAT FOR A HIGH-PRESSURE VALVE IN A HORIZONTAL BORING MILL of the coarse feed is to insure the tool getting over all the casting without wearing away io any extent, thus insuring parallel surfaces. he next step is to finish the seats for the main bearings. These must be accurately machined to insure a good fit and they must all be in line to. insure the shaft being fitted without unnecessary scraping. The bed is care- fully tested to make sure that its upper surface is flat and true, otherwise trou- ble would develop when the engine was assembled.. The bed is now taken to a ra- dial drill where the various holes fcr bolts, etc., "are drilled, reamed and _ tapped. The columns also require careful finishing. Work on these parts consists of plan- ing the bottom, 'the seat a FIG. 7--HOW THE CRANK WEBS ARE SURFACED--SIX OF THESE MEMBERS ARE LOCATED ON THE PLATEN OF A 60 X 60-INCH PLANER AND SURFACED AT ONE OPERATION--THE CHEEKS MUST BE PARALLEL TO INSURE ACCURACY