First, I needed to extract the sprocket studs. After 30 minutes in the oven at 250°, I was able to break them loose with hand tools and the proper grunting sounds. It cooled down enough by the time I got to the last two that I had to break out the propylene torch, but they all came out.
I chucked it in the lathe, by the outboard bearing face first. I began slowly, carefully, turned the insides of the rough-cast cush-drive bosses so they’d be nicely parallel and concentric. After talking this picture, I did a very light facing skim.
I could then flip it around use three of my freshly machined surfaces to center it in my 3-jaw chuck.
Crank up a bit of WHRRR and I easily cut down the casting with a series of facing cuts. I love how easily cast aluminum machines. The black sharpie line you can see in the photo was was my rough target.
A bit of chamfering, and it looks factory! Not having had much technical training in life, I so enjoy owning a lathe. Even though I’m doing super-basic stuff here, I still can’t help but feel a sense of wonder that I can form and shape metal parts. Not only can I do it by myself, I can do it pretty damn accurately.