How to do it? Internally spherical recess.

[Sergei Slovenija]

Sphere diameter 30 mm. This is part of the hinge assembly where the bronze sphere has stainless ball axles. The body with the inner sphere is also made of stainless steel. With milling work to make pockets, everything is clear.

What equipment is needed to turn a sphere inside a part, except for a lathe? Control methods, cutter type?

 

[Maker]

Easiest way would be a form tool (Well, a CNC lathe would be even easier). You could probably make an extended tool, like a boring bar with a lot of extra clearance, and do it with a ball turner too.

 

[Sergei Slovenija]

Guys, I don't have a CNC and don't have a DRO yet. Equipped with such toys, they are not eager to spend their time on a small piece. Being inundated with orders for months ahead, and giving them the main income. I saw a mechanical device (copier) for turning spheres. But I can't figure out how to turn it inside out. If you don't mind, please attach pictures to your answers. Sometimes it is difficult for me to understand what is at stake, especially in narrow specifics.

 

[Trevorleach]

When I made these stainless steel banjo fittings to suit 42mm petrol pipe I did the internal spherical part on the Cnc milling machine.

View attachment 382431 View attachment 382432

Was it for an engine or some pumping equipment?

 

[Barking Mat]

Pivot bearing ?

My guess.

 

[Pete.]

Sphere diameter 30 mm. This is part of the hinge assembly where the bronze sphere has stainless ball axles. The body with the inner sphere is also made of stainless steel. With milling work to make pockets, everything is clear.

What equipment is needed to turn a sphere inside a part, except for a lathe? Control methods, cutter type?

View attachment 382428 View attachment 382429 View attachment 382430

Seems to me this could be achieved with a ball end mill.

 

[Sergei Slovenija]

Pivot bearing ?

My guess.

spherical Rubik's cube... well, almost

 

[Sergei Slovenija]

Seems to me this could be achieved with a ball end mill.

how?

 

[Trevorleach]

Fuel system to link up the two main petrol tanks on a Panther tank I was involved in the restoration of. There were double ended banjos as well,which were sketchy as hell to turn

Glad I do not have to pay the fuel bill on that!

 

[Pete.]

how?

Well a ball end mill will cut a ball shaped pocket, if you get one the right size.

 

[addjunkie]

Well a ball end mill will cut a ball shaped pocket, if you get one the right size.

Or possibly grind up a form tool, depends how hard the material is.

 

[Agroshield]

Boring head and rotary table.

Milling – how to make – spherical surfaces

go to the home page go to the page above this one – “Milling – how to make…” Milling – how to make – spherical surfaces If the workpiece is mo…

johnfsworkshop.org

The page mostly shows convex surfaces, but it can equally be applied to concave ones.

Edit:

Internal Hemisphere

How would you cut a hemisphere on a manual mill or lathe?

www.practicalmachinist.com

Someone has made an animated version of the process:

See also:

Machining tapered and spherical surfaces : Dowd, Albert Atkins, 1872- : Free Download, Borrow, and Streaming : Internet Archive

43 p. 23 cm

archive.org

 

[Sergei Slovenija]

A bronze ball with cut-off tops is placed in a mating spherical hole made in a stainless steel plate. The ball rotates 90 degrees and can no longer be removed along the axis on which it is threaded. The task is to bore a sphere, not a hemisphere.

 

[m_c]

Without CNC, I think options are quite limited.

Could be done on a lathe with a very compact variation of a ball turning tool, but unless it's a fairly large sphere, there's going to be limit by the tool being strong enough to not simply fail.
It could be done on a mill with a ball end mill, but only if the cut radius is going to be smaller than the access hole i.e. you couldn't have a radius the same size as the full sphere size as you wouldn't get the cutter in. This could be doable in this kind of application where the internal has two flats, so could be designed not to simply be a pure sphere with two sides cut off.
It could also be done with a form tool, but I'd think chatter would be an issue given the large surface that would be getting machined.

I think it could possibly be done on a mill, a rotary table and suitable boring bar, but clearance could be an issue.

Next more specialist step would likely be a copy lathe.

 

[Sergei Slovenija]

I thought about the "ball inside the sphere" functionality and intermediate thoughts are: In fact, we have a half of the universal joint, with a very small angle of oscillation of the star-shaped knife holder (until the drive presses the knives against the die mirror), after which the parts will take a constant orientation. Possible runout 0.01 mm, across the axis of rotation. All this complex geometry and the way the knot is assembled serves one purpose - to hang the ball on two points (two balls with a diameter of 6 mm), across the axis of rotation. You just need to put the balls inside so that both halves of the holder are centered relative to each other and the geometry of the parts has a "fuse" if something goes wrong. The holder rotates at 3,000 rpm.