[meteorite-list] My Uruacu Sphere Project is not going well

From: David & Kitt Deyarmin <bobadebt_at_meteoritecentral.com>
Date: Tue, 21 Aug 2007 22:17:42 -0400
Message-ID: <01c801c7e462$9edd0000$e3f33842_at_David>

I have been processing some Uruacu for a person named Philip who lives in
Brazil.

As part of our agreement he said I could have enough material to make a 50mm
sphere.

I processed a 7kg rock and easily got my sphere rough and it looked like it
was going to make an awesome sphere, it was loaded with inclusions and all
of the end cuts and slices etched really well.

I sent the rough to my machinist and then the project went south. He uses a
5-axis milling machine to turn my rough cube or core into a rough sphere
with a clamping nub.

Normally he's able to machine a sphere with a single insert, he had already
gone through 4 inserts when the sphere sheared off the clamping nub and flew
out of the fixture.

He tried to epoxy it into his fixture but it didn't hold so with nothing to
clamp to he had no choice but to send it to me as is.


http://i131.photobucket.com/albums/p298/BobaDebt/Uruacu/48mmSphere2.jpg



I contacted John, the guy that makes my Chondrite spheres and asked him if
he could finish the job.

He said he could grind it in by hand and then polish it on his 3-head sphere
machine so I sent it off and waited more then a month.

He was able to finish the job but he couldn't keep it to 50mm. The machinist
cuts it to .010" over 50mm which is fine for me to polish but it didn't give
John enough material to work with so it ended up being 48mm.

That doesn't sound like a lot but when every other sphere in my collection
is 50mm it makes it stand out A LOT.

Another problem was the finish was not up to par for etching, I guess the
included material mixed with the grit and caused a lot of scratches.

Normally I have the nub on my rough sphere which I chuck in my drill press
and this makes the polishing process very easy.

Well, John sent back a sphere with no nub and a finish equivalent to what
you get from 80 grit sand paper.

I thought about it for a while and determined my only option was to epoxy a
bolt to the sphere to act as the drive nub, it work well and I spent about
30 minutes polishing it up to 600 grit and it looks fantastic


http://i131.photobucket.com/albums/p298/BobaDebt/Uruacu/48mmSphere1.jpg


Which is just another reason to be upset, it's going to finish out to a
beautiful sphere but it's too small, so it's not a keeper.

Philip was kind enough to allow me to use the only remaining piece that
large enough for a 50mm sphere for a second attempt so now I have to start
the process all over again.

If it's successful I will try to sell this one but I'll never recoup the
money we would have made selling it as slices, but Philip is a great guy and
doesn't seemed to be bothered by that.
Received on Tue 21 Aug 2007 10:17:42 PM PDT