The 'Cowling' / Prop bearing retaining ring


As I mentioned earlier, I have chosen to forego the cowling and have replaced it functionally with this disk, designed to fix the front prop bearing into place and absorb thrust loads. This part is best made of steel. I chose 303 Stainless.

  In retrospect, mild steel might have been a better choice, as this alloy, even though it is classified as free-machining, is not fun to turn. The dimensions of my thrust retainer is 36mm OD, 18mm ID, to retain the bearing but clear the moving inner race.

The disk is turned to 36mm in the lathe. The chips came off blue. Lots of heat generated. Carbide tooling is suggested.

The slug is bored to the required 18mm ID. Not shown, the slug is drilled 3-48 clear in the correct bolt pattern to mate with the Prop Shaft Housing, Part 158, again using DRO coordinate drilling in the vertical mill.
Back in the lathe, the retainer is parted. I found that rigidity is critical here, as once the tool hit the drilled holes, the vibration was bad and the work tended to wander, binding the parting tool. Again, a multiple parting cut was executed. See the 5th picture on the Prop Shaft Housing for details on this method.
The finish as the part came off the slug was very nice, so minimal polishing was required. I did deburr and generally clean up the retainer. The finished result is shown here mounted on the Prop Shaft Housing with 3-48 SHCS. I have the option of later countersinking for flat head cap screws, which would present a neater appearence.

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