Turbine Shaft Housing Part III

Construction continues on the Turbine Shaft Housing.

  Rather than using math or a DRO to lay out the holes in the rear of the gear case, we can make good use of a bearing and the 10-32 spigot retaining screw to temprarily hold the two parts together in perfect alignment. A streak of blue helps to identify the holes.

First, a bearing is inserted into the housing. Since the bearing bore depth is only 3.35mm, a good portion of the bearing protrudes. This is inserted into the gear case, and the bearing acts as a dowel pin to align. The housing is rotated so that the spot-faced 10-32 spigot hole is aligned, and a 10-32 cap screw is used to secure.

Using a close-fitting drill, the hole locations are marked by hand. After the shaft housing is removed, the spots are first prick punched, then centre punched. Drilling and tapping 4-40 / 3mm completes the operation. The parts are deburred and generally cleaned.
The housing firmly mated with the gear case. Note that I still haven't beveled the rear of the gear case... leaving this square for now gives me workholding options for later turning and/or milling operations. Note too how the spigot retaining screw becomes part of the security of the shaft housing. It looks neat, too.
The other side of the gear case, with the prop shaft housing mounted. There is still no udercut. Again, this is left solid for now.

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