I'm looking for some large (6+ inches dia) spheres that
can be machined to suit my needs.

They need to have some "heft" and be reasonably durable
(glass would be ideal but hard to "machine" and too
fragile -- or, so says my "glass guy")

Bowling balls (10-pin) are the obvious idea that comes
to mind. But, they aren't homogenous materials (and,
I'm not sure I could get information on their internal
composition other than empirically)

[No seams allowed]

Hardwoods are another possibility but I'm not sure
how they would fare, over time (presumably, such things
are dried before being created).

Additive methods would also be a possibility. But, then
similar issues present when dealing with such a large mass
trying to "cure" evenly.

I'm meeting with a glass artisan next week to see if he
can shed some light on fabrication alternatives but don't
hold out much hope for that (see above).

Steel would be too heavy. Aluminum might be too soft
(too easily marred)

Any other materials I can explore?

søndag den 6. august 2023 kl. 02.51.38 UTC+2 skrev Don Y:
> I'm looking for some large (6+ inches dia) spheres that
> can be machined to suit my needs.
>
> They need to have some "heft" and be reasonably durable
> (glass would be ideal but hard to "machine" and too
> fragile -- or, so says my "glass guy")
>
> Bowling balls (10-pin) are the obvious idea that comes
> to mind. But, they aren't homogenous materials (and,
> I'm not sure I could get information on their internal
> composition other than empirically)

bowling balls are cast with a weight inside

but if aluminium is too soft I don't see any plastic being hard enough

>
> [No seams allowed]
>
> Hardwoods are another possibility but I'm not sure
> how they would fare, over time (presumably, such things
> are dried before being created).
>
> Additive methods would also be a possibility. But, then
> similar issues present when dealing with such a large mass
> trying to "cure" evenly.
>
> I'm meeting with a glass artisan next week to see if he
> can shed some light on fabrication alternatives but don't
> hold out much hope for that (see above).
>
> Steel would be too heavy. Aluminum might be too soft
> (too easily marred)
>
> Any other materials I can explore?

https://www.ebay.com/itm/144428340712 ?

On 8/6/2023 12:00 AM, Lasse Langwadt Christensen wrote:
> søndag den 6. august 2023 kl. 02.51.38 UTC+2 skrev Don Y:
>> I'm looking for some large (6+ inches dia) spheres that
>> can be machined to suit my needs.
>>
>> They need to have some "heft" and be reasonably durable
>> (glass would be ideal but hard to "machine" and too
>> fragile -- or, so says my "glass guy")
>>
>> Bowling balls (10-pin) are the obvious idea that comes
>> to mind. But, they aren't homogenous materials (and,
>> I'm not sure I could get information on their internal
>> composition other than empirically)
>
> bowling balls are cast with a weight inside
>
> but if aluminium is too soft I don't see any plastic being hard enough

Hollow steel and aluminum spheres can be found at various decorative
metal works and ball bearing shops online e.g.

<https://vxb.com/products/christmas-decoration-7-inch-stainless-steel-mirror-shiny-ball?variant=43579655061739>

A solid 6" aluminum sphere would probably be a custom job, though, and
cost the better part of a grand

On 8/5/2023 8:51 PM, Don Y wrote:
> I'm looking for some large (6+ inches dia) spheres that
> can be machined to suit my needs.
>
> They need to have some "heft" and be reasonably durable
> (glass would be ideal but hard to "machine" and too
> fragile -- or, so says my "glass guy")
>
> Bowling balls (10-pin) are the obvious idea that comes
> to mind.  But, they aren't homogenous materials (and,
> I'm not sure I could get information on their internal
> composition other than empirically)
>
> [No seams allowed]
>
> Hardwoods are another possibility but I'm not sure
> how they would fare, over time (presumably, such things
> are dried before being created).
>
> Additive methods would also be a possibility.  But, then
> similar issues present when dealing with such a large mass
> trying to "cure" evenly.
>
> I'm meeting with a glass artisan next week to see if he
> can shed some light on fabrication alternatives but don't
> hold out much hope for that (see above).
>
> Steel would be too heavy.  Aluminum might be too soft
> (too easily marred)
>
> Any other materials I can explore?
>

Limestone?

<https://www.theclassycottage.com/studio-a-travertine-sphere-6-7-70021.aspx>

On Saturday, August 5, 2023 at 9:33:37 PM UTC-7, bitrex wrote:
> On 8/5/2023 8:51 PM, Don Y wrote:
> > I'm looking for some large (6+ inches dia) spheres that
> > can be machined to suit my needs.
> >
> > They need to have some "heft" and be reasonably durable
....
> > Steel would be too heavy. Aluminum might be too soft
> > (too easily marred)
> >
> > Any other materials I can explore?
> >
> Limestone?
>
> <https://www.theclassycottage.com/studio-a-travertine-sphere-6-7-70021.aspx>

Oh, think big: the grand kugel is a museum item they let you touch.
Don't hurt it!

<https://www.atlasobscura.com/places/the-grand-kugel-richmond-virginia>

On a sunny day (Sat, 5 Aug 2023 17:51:16 -0700) it happened Don Y
<blockedofcourse@foo.invalid> wrote in <uamqqg$1uf6n$1@dont-email.me>:

>I'm looking for some large (6+ inches dia) spheres that
>can be machined to suit my needs.
>
>They need to have some "heft" and be reasonably durable
>(glass would be ideal but hard to "machine" and too
>fragile -- or, so says my "glass guy")
>
>Bowling balls (10-pin) are the obvious idea that comes
>to mind. But, they aren't homogenous materials (and,
>I'm not sure I could get information on their internal
>composition other than empirically)

Old tech:
https://en.m.wikipedia.org/wiki/Stone_spheres_of_Costa_Rica

On 06/08/2023 01:51, Don Y wrote:
> I'm looking for some large (6+ inches dia) spheres that
> can be machined to suit my needs.
>
> They need to have some "heft" and be reasonably durable
> (glass would be ideal but hard to "machine" and too
> fragile -- or, so says my "glass guy")

>
> I'm meeting with a glass artisan next week to see if he
> can shed some light on fabrication alternatives but don't
> hold out much hope for that (see above).

If you're looking at solid glass spheres why does your guy think they
are fragile? Even thick hollow glass is strong in compression. If you
hit them with something hard, you can damage the surface, but that would
happen with metal spheres too.

There seem to be quite a few available on the internet at 6+ inches, so
the "machining" doesn't seem to be much of an issue (although the cost
might be!).

--

Jeff

On 8/5/2023 9:33 PM, bitrex wrote:
>> Steel would be too heavy.  Aluminum might be too soft
>> (too easily marred)
>>
>> Any other materials I can explore?
>
> Limestone?
>
> <https://www.theclassycottage.com/studio-a-travertine-sphere-6-7-70021.aspx>

Oooooo.... that's a good idea! They don't seem to state a "shipping
weight" (to get an idea of it's actual weight).

Obviously, the material can be "shaped" but I wonder how practical
that is for "random" shaping? And, how prevalent the tools and
skills to do so?

[The bowling ball idea made sense in that folks can drill balls
in most alleys so I would assume there is a fair supply of
people capable of "machining" bowling balls -- beyond drilling
finger holes and engraving the bowler's name!]

There's a store, here, that has a large sphere floating (though just
barely) on a pressurized jet of water. IIRC, it's a fair bit larger
(maybe 10-12 inches?). I've always assumed it to be made of marble
but, that may just be the association with "marbles" (aggies) in my
mind as I've never stopped to examine it (I don't think the store
management would be keen on folks messing with it)

I will have to make a trip for some discrete inspection...

Thanks!

On 8/5/2023 10:29 PM, whit3rd wrote:
> Oh, think big: the grand kugel is a museum item they let you touch.
> Don't hurt it!
>
> <https://www.atlasobscura.com/places/the-grand-kugel-richmond-virginia>

That is exactly the sort of "sphere" I'd mentioned in my reply
to bitrex, above.

On 8/5/2023 9:00 PM, Lasse Langwadt Christensen wrote:
>> Steel would be too heavy. Aluminum might be too soft
>> (too easily marred)
>>
>> Any other materials I can explore?
>
> https://www.ebay.com/itm/144428340712 ?

That gives me an idea of what the sphere bitrex mentioned might weigh.

And, if "stone" proves to be the right option, then I can just
wait for the Gem & Mineral Show, this winter, to see what I can pick up
locally (let the seller come to me instead of the other way around)

On 8/5/2023 9:24 PM, bitrex wrote:
> Hollow steel and aluminum spheres can be found at various decorative metal
> works and ball bearing shops online e.g.

Hollow wouldn't have enough heft.

> A solid 6" aluminum sphere would probably be a custom job, though, and cost the
> better part of a grand

Solid needs to be some semi-homogeneous material. Like filling a
hollow sphere with a flowable material that would harden in
that shell (then, deciding if the shell should be removed or
worked around)

On 8/6/2023 12:13 AM, Jeff Layman wrote:
> On 06/08/2023 01:51, Don Y wrote:
>> I'm looking for some large (6+ inches dia) spheres that
>> can be machined to suit my needs.
>>
>> They need to have some "heft" and be reasonably durable
>> (glass would be ideal but hard to "machine" and too
>> fragile -- or, so says my "glass guy")
>
>>
>> I'm meeting with a glass artisan next week to see if he
>> can shed some light on fabrication alternatives but don't
>> hold out much hope for that (see above).
>
> If you're looking at solid glass spheres why does your guy think they are
> fragile? Even thick hollow glass is strong in compression. If you hit them with
> something hard, you can damage the surface, but that would happen with metal
> spheres too.

The glass approach would be to *mold*/cast the desired features in the
glass while it is still in a liquid state. I am assuming this would
be considerably less costly than trying to "machine" a solid glass
sphere.

[Though other materials would likely have an opposite advantage; machine
instead of cast]

> There seem to be quite a few available on the internet at 6+ inches, so the
> "machining" doesn't seem to be much of an issue (although the cost might be!).

On 06/08/2023 01:51, Don Y wrote:
> I'm looking for some large (6+ inches dia) spheres that
> can be machined to suit my needs.

<snip>

> Any other materials I can explore?

Machinable Ceramics?

--
Cheers
Clive

On Saturday, August 5, 2023 at 7:51:38 PM UTC-5, Don Y wrote:
> I'm looking for some large (6+ inches dia) spheres that
> can be machined to suit my needs.
>
> They need to have some "heft" and be reasonably durable
> (glass would be ideal but hard to "machine" and too
> fragile -- or, so says my "glass guy")
>
> Bowling balls (10-pin) are the obvious idea that comes
> to mind. But, they aren't homogenous materials (and,
> I'm not sure I could get information on their internal
> composition other than empirically)
>
> [No seams allowed]
>
> Hardwoods are another possibility but I'm not sure
> how they would fare, over time (presumably, such things
> are dried before being created).
>
> Additive methods would also be a possibility. But, then
> similar issues present when dealing with such a large mass
> trying to "cure" evenly.
>
> I'm meeting with a glass artisan next week to see if he
> can shed some light on fabrication alternatives but don't
> hold out much hope for that (see above).
>
> Steel would be too heavy. Aluminum might be too soft
> (too easily marred)
>
> Any other materials I can explore?y

What are pool or billiard balls made of? They're too small but you'd get a start. I can't think of anything
unique to farming that would fit the bill.

On Sunday, August 6, 2023 at 7:17:21 AM UTC-4, Dean Hoffman wrote:
> On Saturday, August 5, 2023 at 7:51:38 PM UTC-5, Don Y wrote:
> > I'm looking for some large (6+ inches dia) spheres that
> > can be machined to suit my needs.
> >
> > They need to have some "heft" and be reasonably durable
> > (glass would be ideal but hard to "machine" and too
> > fragile -- or, so says my "glass guy")
> >
> > Bowling balls (10-pin) are the obvious idea that comes
> > to mind. But, they aren't homogenous materials (and,
> > I'm not sure I could get information on their internal
> > composition other than empirically)
> >
> > [No seams allowed]
> >
> > Hardwoods are another possibility but I'm not sure
> > how they would fare, over time (presumably, such things
> > are dried before being created).
> >
> > Additive methods would also be a possibility. But, then
> > similar issues present when dealing with such a large mass
> > trying to "cure" evenly.
> >
> > I'm meeting with a glass artisan next week to see if he
> > can shed some light on fabrication alternatives but don't
> > hold out much hope for that (see above).
> >
> > Steel would be too heavy. Aluminum might be too soft
> > (too easily marred)
> >
> > Any other materials I can explore?y
>
> What are pool or billiard balls made of? They're too small but you'd get a start. I can't think of anything
> unique to farming that would fit the bill.

https://capitalresin.com/phenolic-resin-and-the-production-of-billiard-balls/

On Sat, 5 Aug 2023 17:51:16 -0700, Don Y
<blockedofcourse@foo.invalid> wrote:

>I'm looking for some large (6+ inches dia) spheres that
>can be machined to suit my needs.
>
>They need to have some "heft" and be reasonably durable
>(glass would be ideal but hard to "machine" and too
>fragile -- or, so says my "glass guy")
>
>Bowling balls (10-pin) are the obvious idea that comes
>to mind. But, they aren't homogenous materials (and,
>I'm not sure I could get information on their internal
>composition other than empirically)
>
>[No seams allowed]
>
>Hardwoods are another possibility but I'm not sure
>how they would fare, over time (presumably, such things
>are dried before being created).
>
>Additive methods would also be a possibility. But, then
>similar issues present when dealing with such a large mass
>trying to "cure" evenly.
>
>I'm meeting with a glass artisan next week to see if he
>can shed some light on fabrication alternatives but don't
>hold out much hope for that (see above).
>
>Steel would be too heavy. Aluminum might be too soft
>(too easily marred)
>
>Any other materials I can explore?

What's the application?

On 8/6/2023 2:07 AM, Clive Arthur wrote:
> On 06/08/2023 01:51, Don Y wrote:
>> I'm looking for some large (6+ inches dia) spheres that
>> can be machined to suit my needs.
>
> <snip>
>
>> Any other materials I can explore?
>
> Machinable Ceramics?

Can ceramics be (easily/economically) machined? I know they
can be formed in molds -- which would seem the easier way
to embed features.

OTOH, I believe there is shrinkage from that process -- which
might impact repeatability (?)

On 8/6/2023 4:17 AM, Dean Hoffman wrote:
>> Any other materials I can explore?y
>
> What are pool or billiard balls made of? They're too small but you'd get a start.

Dunno. I'd have to check. But, maybe there are limitations on size
that affect dimensional stability? I.e., why aren't bowling balls
made of the same (?) material? Bocce? 9-pin? etc.

> I can't think of anything
> unique to farming that would fit the bill.

Pumpkins? :>

On Sun, 6 Aug 2023 00:47:34 -0700, Don Y <blockedofcourse@foo.invalid>
wrote:

>
>There's a store, here, that has a large sphere floating (though just
>barely) on a pressurized jet of water. IIRC, it's a fair bit larger
>(maybe 10-12 inches?). I've always assumed it to be made of marble
>but, that may just be the association with "marbles" (aggies) in my
>mind as I've never stopped to examine it (I don't think the store
>management would be keen on folks messing with it)

http://www.sorvikivi.com/eng/index.html

This company can make granite balls from 12 cm to 3 m diameter.

At least the 50 cm version can be easily rotated by hand when the ball
is sitting on the pressurized water jet.

upsidedown@downunder.com wrote:

> On Sun, 6 Aug 2023 00:47:34 -0700, Don Y <blockedofcourse@foo.invalid>
> wrote:
>
>>
>>There's a store, here, that has a large sphere floating (though just
>>barely) on a pressurized jet of water. IIRC, it's a fair bit larger
>>(maybe 10-12 inches?). I've always assumed it to be made of marble
>>but, that may just be the association with "marbles" (aggies) in my
>>mind as I've never stopped to examine it (I don't think the store
>>management would be keen on folks messing with it)
>
> http://www.sorvikivi.com/eng/index.html
>
> This company can make granite balls from 12 cm to 3 m diameter.
>
> At least the 50 cm version can be easily rotated by hand when the ball
> is sitting on the pressurized water jet.

Anyone measured the radioactivity of these products?

Granite emits radon, beta and gamma radiation. The amount is normally very
low but easily detectable.

--
MRM

On 06/08/2023 17:12, Don Y wrote:
> On 8/6/2023 2:07 AM, Clive Arthur wrote:
>> On 06/08/2023 01:51, Don Y wrote:
>>> I'm looking for some large (6+ inches dia) spheres that
>>> can be machined to suit my needs.
>>
>> <snip>
>>
>>> Any other materials I can explore?
>>
>> Machinable Ceramics?
>
> Can ceramics be (easily/economically) machined?  I know they
> can be formed in molds -- which would seem the easier way
> to embed features.
>
> OTOH, I believe there is shrinkage from that process -- which
> might impact repeatability (?)

Machinable Ceramics can be machined, of course. Google it, loads of
hits. MACOR is one type.

I had some pretty complex shapes made many years ago. The ceramic was
CNC machined to a high tolerance with a good surface finish. Carbide
tools work very well, high speed steel tools work quite well.

--
Cheers
Clive

On 2023-08-06 18:33, Mike Monett VE3BTI wrote:
> upsidedown@downunder.com wrote:
>
>> On Sun, 6 Aug 2023 00:47:34 -0700, Don Y <blockedofcourse@foo.invalid>
>> wrote:
>>
>>>
>>> There's a store, here, that has a large sphere floating (though just
>>> barely) on a pressurized jet of water. IIRC, it's a fair bit larger
>>> (maybe 10-12 inches?). I've always assumed it to be made of marble
>>> but, that may just be the association with "marbles" (aggies) in my
>>> mind as I've never stopped to examine it (I don't think the store
>>> management would be keen on folks messing with it)
>>
>> http://www.sorvikivi.com/eng/index.html
>>
>> This company can make granite balls from 12 cm to 3 m diameter.
>>
>> At least the 50 cm version can be easily rotated by hand when the ball
>> is sitting on the pressurized water jet.
>
> Anyone measured the radioactivity of these products?
>
> Granite emits radon, beta and gamma radiation. The amount is normally very
> low but easily detectable.

Radiation from granite is no issue unless you're living on a mountain's
worth of the stuff. And even then. It's not because some granite formations
emit radiation that all do.

Jeroen Belleman

On 8/6/2023 3:47 AM, Don Y wrote:
> On 8/5/2023 9:33 PM, bitrex wrote:
>>> Steel would be too heavy.  Aluminum might be too soft
>>> (too easily marred)
>>>
>>> Any other materials I can explore?
>>
>> Limestone?
>>
>> <https://www.theclassycottage.com/studio-a-travertine-sphere-6-7-70021.aspx>
>
> Oooooo.... that's a good idea!  They don't seem to state a "shipping
> weight" (to get an idea of it's actual weight).
>
> Obviously, the material can be "shaped" but I wonder how practical
> that is for "random" shaping?  And, how prevalent the tools and
> skills to do so?

Companies that do e.g. gravestones and memorial monuments might be a
good place to ask.

> [The bowling ball idea made sense in that folks can drill balls
> in most alleys so I would assume there is a fair supply of
> people capable of "machining" bowling balls -- beyond drilling
> finger holes and engraving the bowler's name!]
>
> There's a store, here, that has a large sphere floating (though just
> barely) on a pressurized jet of water.  IIRC, it's a fair bit larger
> (maybe 10-12 inches?).  I've always assumed it to be made of marble
> but, that may just be the association with "marbles" (aggies) in my
> mind as I've never stopped to examine it (I don't think the store
> management would be keen on folks messing with it)
>
> I will have to make a trip for some discrete inspection...
>
> Thanks!
>

jeroen <jeroen@nospam.please> wrote:

> Radiation from granite is no issue unless you're living on a mountain's
> worth of the stuff. And even then. It's not because some granite
> formations emit radiation that all do.
>
> Jeroen Belleman

Radon gas from granite collects in enclosed spaces like basements. It is
extremely dangerous and causes lung cancer. See

Radiation and Health Effects

Most cancers from radon are produced by radon daughter decay products
(polonium, 3 isotopes; bismuth, 1 isotope; and lead, 3 isotopes) adhering
to the delicate cell lining and passageways leading to the lungs.

https://www.sciencedirect.com/topics/pharmacology-toxicology-and-pharmaceut
ical-science/radon-daughter

Thorium in Thorium Molten Salt Reactors also has dangerous decay products
that include radon. See

The radioactive series of thorium-232

https://www.ld-didactic.de/software/524221en/Content/Appendix/Th232Series.h
tm

If you are living or working in a basement somewhere, you may consider
buying a Radon detector, such as sold on Amazon:

https://www.google.ca/search?q=radon+detector

--
MRM

On 8/6/2023 10:33 AM, jeroen wrote:
> Radiation from granite is no issue unless you're living on a mountain's
> worth of the stuff. And even then. It's not because some granite formations
> emit radiation that all do.

What about *in* a mountain?

<https://en.wikipedia.org/wiki/Cheyenne_Mountain_Complex>

[They used to offer tours of the facility but it's been decades
since I went -- I suspect that has been discontinued (?) ]