Well, it was a nice try, sort of -- and it might even have worked despite a serious head slapping mistake (which I can fix) had I not slipped during the final milling, cutting through a vane. But it would have worked "ugly" in any case, so now I go fix the idiot mistake I made and make a better tool for indexing so I don't slip again. You'll have to be real sharp eyed to see the really dumb mistake here....
Give up? Fundamental math fail. I'd calculated and punched some index marks on the lathe chuck to use with a pointer to get 45 deg spots, and didn't check the math, or count close enough.
Meant to divide by 16 but got 18....so I had this little error at the end of things...Now to go do it right and start over. I'll be blowing black snot for awhile, this stuff is easy to work, but does all become fine graphite powder off the tool that gets in the air. But that was embarrasing enough to be put here, rather than eye candy. You'd think I'd learned to count by now!
I did this in the following order, and this plan looks like it will work.
1" gr rod, in lathe.
Center drill 3/16" for the eventual 10-32 bolt that will hold it to the feedthrough.
Redrill with forstner bit to 3/4" diameter, and desired depth of main hole. (note, about 900 rpm and keep the feed pressure down so as not to shove the graphite back into the lathe chuck -- it's slippery!
Polish outside, this is the last chance.
Using toolpost tool and a 1/16" end mill, cut slots at 45 deg rotations (and next time, make them 45!) Take about 20-30 mils per cut, it will chatter if you try to get through in one -- at 20 mils you can go fast, no problems.
Starting at each cut, cut "up" towards the cut above till there's just a vane left. Use fingertips to keep acoustic resonances damped down. Only cut about half the mill diameter per, and these can be all the way through.
Don't slip with the tool in the hole! Pull that sucker back before touching the lathe chuck!
Sign, only a few hours wasted. This would be a piece of cake on Jerry's machine I bet. I tried to do this all on the lathe as my circle table stinks, and anyway I can't work too close to
the table because of the mill quill hitting.
So, it almost worked. Next time, it will work, pretty sure. Maybe need a beer rather than the morning tea for a little smoother hands.
I was pleasantly surprised that oops-ing on the chuck that cut a vane didn't shatter anything, and that the vanes are slightly flexible but don't shatter at first touch. This is good material to work.