[Rockhounds] sphere-makers: how do you make very tiny spheres?

[Julie Siebel]

Brilliant. I love this list.

Julie

----- Original Message ----- 
From: "Jim Murowchick" <murowchickj at umkc.edu>
To: "Rockhounds at drizzle.com: A mailing list for rock and gem collectors" 
<rockhounds at lists.drizzle.com>
Sent: Sunday, March 15, 2009 1:31 PM
Subject: Re: [Rockhounds] sphere-makers: how do you make very tiny spheres?


> Don-
>    I made some very small pyrite spheres to use as seed crystals for some
> crystal growth work back in 1980 or so.  I'll see if I can describe it, 
> but
> let me know if you want a sketch.
>    The body of the grinder was a ca. 2" x 2" x 1/4" thick slab of 
> something
> (it might have been steel or aluminium, or ceramic--I can't remember) with 
> a
> 1 to 1 1/4" hole drilled through the sides.  A small (maybe 1/16' inch) 
> hole
> came in from one edge so that compressed air could enter the chamber
> tangentially.  A small brass or copper tube extending out from the hole
> allowed some plastic tubing to be attached for the air.  The sides of the
> chamber were covered with a flat plate with a small (ca. 1/4" hole in the
> center of each side.  The hole is covered with a fine mesh on the outside
> face so the air can escape, but not the bead.  The plates are held against
> the body with a couple of those black spring clips.  I don't remember if
> there was some sort of gasket under the plates for a better seal.  If
> needed, a simple O-ring larger than the chamber diameter would work.
>    The cylindrical face in the chamber is lined with a layer of wet/dry
> abrasive paper, glued with rubber cement to the chamber face.  If a polish
> is needed, you might need to use successively finer grits.  I don't know 
> if
> a high polish can be obtained or not--we needed a sphere with a smooth, 
> but
> not polished surface.
>    A small piece of your material is put into the chamber, which is then
> closed up.  Start the compressed air, and the sample will whizz (that's a
> technical term) around and around, becoming rounded in the process.  The
> dust escapes out the sides.  For the work I did, it took less than a 
> minute
> to make a pyrite sphere about 1mm in diameter.
>    With a little experimentation with grits and air flow, and grinding
> time, I think you'll get what you need.  You might need to immerse the
> sphere in a refractive index oil for optical work if the polish is not 
> good.
>    I think the device is described in a back issue of American
> Mineralogist--I'll see if I can track it down.
>
> Cheers,
> Jim
>
>
> On 3/14/09 4:16 PM, "DonH" <donhalterman at verizon.net> wrote:
>
>>
>> Hi,
>>
>> I know some of you make spheres, usually of the 1/2" to 6" (or whatever)
>> variety.  I know how these are made and have seen the equiment.
>>
>> However, is anyone familiar with making extremely tiny spheres, less
>> than 1 millimeter in size?  I would imagine the milling process as I
>> know it doesn't scale down that small.
>>
>> Thanks,
>> Don
>>
>>
>
> -- 
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