machining inside of sphere?

Is there an easy way to machine the inside surface of a (hemi-) sphere?
Thanks.
-- Peter Fairbrother

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"Peter Fairbrother" wrote in message

Most lathe radius turner / ball turner accessories will do this by design.
Andrew
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Using a rotary table and a boring head with the spindle chanted at 45 degrees.
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On 16/05/2016 16:45, Anzaniste wrote:

There seems to be a bit more to it than that. Scroll down this link to see response by Slicerman with a picture of the theory and formula. http://www.practicalmachinist.com/vb/general/internal-hemisphere-138401/ Needs a bit of thought to translate to internal hemisphere
Cheers Henry
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On 16/05/2016 16:45, Anzaniste wrote:

I posed the question to retired friend who was a miller among other things. He suggested putting a fly-cutter with a radius of swing equal to that of the required hemisphere, into a vertical mill. Mount a rotary table with its axis parallel to the machine bed and aligned with the vertical of the fly-cutter. Attach the work-piece to the rotary table. Apply feed with the mill table horizontal feed and rotate the rotary table to shape the hemisphere.
Cheers Henry
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Thanks all. Perhaps I should have been clearer - I need a fairly perfect hemisphere - it's for a mirror.
I think this method comes closest - but I will probably buy a large ball-bearing and use it as a mould.
Ta again,
-- Peter Fairbrother
On 21/05/16 15:06, Dragon wrote:

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On 5/15/2016 1:56 PM, Peter Fairbrother wrote:

When I worked for a bearing manufacture as a tool and die maker we lathe turned the halves, weld, heat treat, chrome and then sent the spheres for roll grinding and then removed as needed to make it the hemisphere. The ones I did where like 5 inch outside, 4.5 inch inside diameter for display items back in the 70's. Now I'm sure the inside would be done by cnc machining on case hardened balls?
What are your plans? Jim A
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