Turbine Shaft Housing Part I

Part 145, the turbine shaft housing, is an important part which is a challenge to make with accuracy. In relative shape, it is similar to the MW54 shaft tunnel and performs much of the same function.

  Once again, a decently sized aluminum blank is chucked, faced, and turned to the flange major diameter. The flange will hereafter refer to the portion of the housing which mates with either the gearbox case or the "spider". For reasons which I will make clear later, I deviated from the print a bit and made the gear case flange a slightly greater diameter than Mike's.

Here, the future gear case flange is closest to the chuck. The remainder of the housing is turned to the minor diameter defined by the mating of this part with the "spider".

  Since the interior of this part is heavily radiused, I determined how much "meat" to leave at either end, and marked this off with a parting tool plunged to the minor diameter of 19mm + a bit for later cleanup. This isolates the "no-cut" portion of the housing, while the middle may be effectively hogged without harming the ends.
With the middle turned to 19mm +, (note roughness, to be cleaned to 19mm later during the filleting), the thickness of the flanges at either end are marked off with blue and a scribe. The trick here is to radius the spider flange up to the scribed line, and to a 19mm diameter at the bottom.
The radius cut in progress. This is a lot of fun because it requires some clever jogging of the X,Y axes. Don't even attempt to grind a radius tool to the correct profile; on all but the heaviest lathes, it would chatter horribly.
With the spider flange radius turned, we turn next to the gear case flange radius. Using the same process, the radius is cut, and now is the time to smooth everything out and turn the minor OD to the print 19mm.
The spider flange end is profiled and bored (shown here) for the correct bearing. By now, we are becoming adept at boring for these bearings... there are a LOT of them.

In part 2, we part off the housing and work on the gear case flange end.

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