help with turning (or otherwise shaping) a small dome

A spherical surface meeting your specification would have a radius of 1.3". This is not out of the question for a ball turner. If you elect to make the domes by hand, you can make a template out of sheet metal to check your curves. This should ensure reasonable repeatability.
 
I went through a couple iterations to try to make concave and convex, and finally domes. I used 80/20 because it was reusable and pretty much infinitely scalable. And now totally repeatable.

The first one was based off my 10" rotary table with a stationary arm opposite. It worked ok but was hard to get accurately setup and that RT is just too heavy. It was also cumbersome to switch the cutter and work to make convex and concave. So the present one is two independent arms on one rail central rail with little 3" cheap rotary ables as the pivots. When the cutter is swinging it cuts concave, when the cutter is locked and the work is swinging it cuts convex. I put another 3" on the work head and it cuts domes. Sorry for the small pics, I didn't know what I was doing then.image.jpgimage.jpgimage.jpgimage.jpgimage.jpgimage.jpg
 
I went through a couple iterations to try to make concave and convex, and finally domes. I used 80/20 because it was reusable and pretty much infinitely scalable. And now totally repeatable.

The first one was based off my 10" rotary table with a stationary arm opposite. It worked ok but was hard to get accurately setup and that RT is just too heavy. It was also cumbersome to switch the cutter and work to make convex and concave. So the present one is two independent arms on one rail central rail with little 3" cheap rotary ables as the pivots. When the cutter is swinging it cuts concave, when the cutter is locked and the work is swinging it cuts convex. I put another 3" on the work head and it cuts domes. Sorry for the small pics, I didn't know what I was doing then.View attachment 281494View attachment 281495View attachment 281496View attachment 281497View attachment 281498View attachment 281499


This is similar to what I was envisioning if I used the belt sander with a fixture and a curved slot (albeit less complex, not adjustable and not as cool as yours)
 
Thanks. Your description sounded somewhat like mine, that's why I posted. The coolest parts is the 80/20 which I was lucky to bumble onto on the local CL. There is a long way between an idea and something that works. It makes it possible to have an idea evolve. It's why they call it big boy erector set :)
 
Thanks. Your description sounded somewhat like mine, that's why I posted. The coolest parts is the 80/20 which I was lucky to bumble onto on the local CL. There is a long way between an idea and something that works. It makes it possible to have an idea evolve. It's why they call it big boy erector set :)

And I have had an 80/20 "kit" in my Amazon cart for ....ohhh, a long time now !
 
while 80/20 is amazing stuff, it's also a very "deep" system. There is a lot to it like "series" besides dimensions. 10 series is in inches, 15 series is metric. I was lucky mine was an old CNC router 4x8 table that the electronic's had been salvaged and originally they were just going to scrap the frame and all it's hardware. So I got a total of 74' of 2x2 10 series extrusions and a bunch of angles, braces and a ton of hardware. All this stuff is proprietary but there are some outfits on eBay that sell "equivalent" and that helps with the cost. If I would have bought it new it would have been 4 or 5x's as much. I've since tried to buy some local and it's basically impossible so all the other stuff like linear bearings, the gear racks and pinions and more hardware has all been off eBay. All of it new.
 
Ever see or do any wood turning? Same thing, except in metal. It is all done free hand and can create almost any shape you need. Look on Youtube. We also discussed them here: https://www.hobby-machinist.com/threads/gravers-for-turning.56828/

Yes I do turn on a wood lathe.
How would you compare the safety / level of control and dexterity needed to use safely ?
Wood is fairly forgiving considering the big difference between it and the metal tool being used, and also the turning tools tend to be very large levers/handles in relation to the cuts/depth being taken - I guess what I am saying is that this seems a bit scary of a proposition at first blush to me.

It is a very interesting idea I would like to learn more about though...
 
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