The Home Machinist!

Old Pierre Vernier 1580 - 1637 would be roiling over in his grave if heard all the people using his name in conjunction with those devices with "Dials" or "digital readouts" on them. I don't know if it's ignorance or simply laziness. (Probably not stupidity)
...lew...

Not true. It all depends on where you are. Here in Abq. we have a good sharpening service that we have used for years for end mills as small as 3/8" and up to 3/4" at prices that make it economical.
...lew...

Anyone who doesn't tell you where they are, isn't serious about wanting help.
...lew...

You'll need a lathe for sure and a "radius turner" . I've done this many times. It's even possible to make the hemisphere a bit deeper than the radius. The tool bit needs to be a bit different than the common one but it's no great problem . I'll be happy to send you some pix if wanted.
...lew...

Yes I can BUT the compound on the lathes I have access to are very suitable to do this on. First off they have nearly 5 inches of travel and a straight side that a dial indicator can follow. So I made a fixture that sits on the ways and measures how far the side of the compound moves while moving th...

I suspect a 4 C . I have a set at school so can show a pix compared to 5C next week, but don't have any 3 C to compare.
...lew...

Metal shop in the garage ( heaver machinery ), wood shop in the separate bldg. A few duplicate hand tools (shouldn't require too many).
...lew...

< I didn't know one crowned pulley was enough.> That should be the first sentence in ANY discussion of flat belt pulleys.
...lew...

After googling " throne of a mariner's astrolabe" I don't see any place where that sort of joint is needed. I am wondering if the revolver joint is "built-up". A friend of 30+ years ago had a revolver like that but I wasn't into machining then so it never would have occurred to me to wonder or look ...

I'm probably old enough to be your grandfather and I have one exactly like that that I bought in 1954 but no idea of the model number.
...lew...

I've sawed it drilled it for years in the electronics racket both paper filled and linen filled. Only effect I've ever noticed it it stinks a bit.
Of course pleasant/vile odor is a subjective thing.
...lew...

It also helps a LOT to use one of the lubricant sticks on the blade when cutting Aluminum. The one I'm using is white and in a tube like caulk comes in touch it to both sides of the blade while running long enough to allow the blade to go around a couple times. For long cuts touch it again after a c...