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pune, 1910 allowed for shrinking being 0.001- inch for each diametrical inch. Care is exercised to make three tions surfaces, that is, the two por- that are to be shrunk in the webs and the center portion that bears in the connecting rod bearings, are parallel. This is especially essen- tial in the case of the center bearing portion for if this is tapered unneces- sary scraping in the assembly opera- tion is called for in fitting the bear- ings. This portion of the pin is also carefully calipered with micrometers to make sure that it is round, other- wise a good fit cannot be made. In making the shaft sections, they sure that all. THE MARINE REVIEW stick slightly while being positioned it might contract to the extent of gripping the shaft tightly before it was properly seated. Should this hap- pen, the only remedy would be to cut away the web which, of course, would ruin it and at the same time render valueless its .mate with which it was bored and keyseated. In shrinking, the webs are posi- tioned by means of the assembling fixture illustrated in Fig. 6.. This con- sists of five locating members, fitted with removable caps, to accommodate the shaft sections. These locating members slide on. a_ cast-iron bed plate and are kept in the correct 281 webs and shafts are placed in posi- tion by means of a traveling crane. After all the webs are shrunk in place, the next step is to bolt the two sections together at the coupling, after which the shaft is mounted in an engine lathe, as shown in Fig. 13, where the final finishing cut is taken over the shaft. .The shaft is located on its centers and driven by the face plate. It is also steadyrested at the coupling. The finishing chip must be taken carefully as upon it depends the true running .of the shaft. If care- fully carried out, the shaft will run true within close limits. As a matter of fact,. the -company has made a ~ FIG. 13--THE LAST OPERATION ON 'HE CRANKSHAFT CONSISTS OF TURNING THE STRAIGHT PORTIONS BETWEEN THE WEBS--THIS LATHE IS RUN BACKWARD TO AVOID CHATTER MARKS are first roughed out .all over on an engine lathe after which the portions that are to be shrunk in the webs are carefully finished, leaving the correct amount of oversize for shrinking. The ends of the couplings are next carefully faced. Next .the - keyseats to position the cranks and eccentrics are cut.. The keyseating is done on a shaper. As the keys are standard sizes, the seats are made slightly undersize to insure a driving fit. The bolt holes -in the: couplings. are next drilled and. reamed. -This work. is generally done on a horizontal boring machine, the holes being located: by means of a jig that fits over the coupling. a et The next-step is to shrink the webs Gver the shafts and pins. This is an important operation that must be car- ried out carefully for if a web should longitudinal position by means of locating blocks which engage a locat- ing slot. The webs are brought up to a black heat in an oil-fired fur- nace especially designed for this pur- pose. The heated web is passed over the end of the shaft which is in posi- tion in the fixture, after which the crank pin is inserted. Next the other web to form the crank is slipped over - the pin and another shaft section in- serted. The caps are now firmly fast- ened in place and the webs allowed to cool which causes them to. contract firmly in place. As the illustration shows, the webs are located in the correct position apart through the medium of a box-section spacer placed between them. results, the assembling fixture must be made carefully as otherwise cor- rect alignment is not possible. The To insure accurate. number of shafts that showed up dead true when tested with a dial indi- Calor, In taking the finishing cut, the lathe is generally run backward to avoid chattering. Why this practice elim- inates chattering, no engineer has yet been able to explain conclusively. Actual practice, however, proves that it does and for this reason it is often employed in taking finishing cuts on crankshafts. eo As the illustration shows, spacers fitted with adjusting screws are placed between the webs to avoid springing the shaft. These must be accurately adjusted for if they are set too tightly- ly the shaft is sprung out of align- ment, while if they are too loose the tailstock center compresses the shaft to a certain extent which also results in the shaft being out of alignment.