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Post by bobby1 on Feb 11, 2010 22:37:44 GMT -5
This one is 7mm (about 1/4") across and I made it from Idocrase for a jewelry piece that I'm working on. I wanted to have a perfect hemisphere shape so I took it to my "sphere" making machine. This machine is a motor mounted vertically with a Jacobs chuck mounted on the shaft. I make my sphere making cups from steel shaft material of various sizes with a cup drilled into the working end. When you make a sphere (or in this case hemisphere) shape you want the cup diameter to be about 2/3 of the size of the sphere. I ground the cab to as close to a hemisphere as I could get on my lapidary grinding wheel. Then I went to this sphere machine and started the grinding using 120/220 grit tumbling media. I mix it with water in a small container and dip the cab in to coat it with grit and rotate the cab on the grinding cup. When it has reached the perfect sphere shape I then go to 400 grit and finish with 600 grit. I polish the cab on my regular carpet covered wheel with Cerium Oxide. Bob
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Post by fishenman on Feb 11, 2010 23:21:43 GMT -5
That is really awesome Bob. What a great idea.
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bobh
having dreams about rocks
Member since September 2009
Posts: 55
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Post by bobh on Feb 11, 2010 23:32:58 GMT -5
Now that is really creative. Nicely done. Bob
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WyckedWyre
fully equipped rock polisher
Member since April 2007
Posts: 1,391
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Post by WyckedWyre on Feb 11, 2010 23:46:03 GMT -5
I want one of those!
:oS
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adrian65
Cave Dweller
Arch to golden memories and to great friends.
Member since February 2007
Posts: 10,777
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Post by adrian65 on Feb 11, 2010 23:53:34 GMT -5
Sir, when you say "big" it's BIG, and when you say "small" it's small ;D
Such a perfect shape and dome on this tiny cab! Thank you for the idea.
Adrian
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Post by Bejewelme on Feb 12, 2010 14:39:27 GMT -5
Bobby: Don't ever admit its not big WOW that is tiny, but shaped perfectly!!!!!!!!
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Post by Toad on Feb 12, 2010 14:46:28 GMT -5
Beautiful cab and clever machine.
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Post by krazydiamond on Feb 12, 2010 19:18:38 GMT -5
small and perfection.
KD
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NDK
Cave Dweller
Member since January 2009
Posts: 9,440
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Post by NDK on Feb 12, 2010 21:34:29 GMT -5
Very cool teeny cab Bob!
What speed do you run the sphere machine at?
Nate
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Post by bobby1 on Feb 12, 2010 22:01:43 GMT -5
Nate, It runs at the speed of the motor which is 1725 rpm. If I were to build another I would look for something where I could control the speed. This one runs too fast and tends to sling the grit out rather than retain it for more efficient grinding. Bob
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fossilbrain
spending too much on rocks
Cookie Monster agate
Member since October 2007
Posts: 360
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Post by fossilbrain on Feb 13, 2010 7:29:35 GMT -5
My grandfather left me a couple this size and I haven't tried anything quite that small yet, so, nice to see how you dopped it
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Post by bobby1 on Feb 13, 2010 12:49:11 GMT -5
When I made the grinding cups I made them with a 1/4-20 threaded shaft so they will fit on the Hi-Tek All in One, Ameritool and the right hand side of the Genie. With the first two machines they have a speed control so they can be slowed down enough so that the grit doesn't sling out very much. Bob
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damammy
has rocks in the head
Member since January 2009
Posts: 697
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Post by damammy on Feb 13, 2010 15:41:04 GMT -5
Wow man when you have a stone that small and do it perfectly you are a master not to mention patient. Donna
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Post by frane on Feb 13, 2010 20:27:34 GMT -5
That is just too cool! You really do amazing work and that one just looks perfect! Fran
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southforkmining
spending too much on rocks
Member since October 2006
Posts: 275
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Post by southforkmining on Feb 13, 2010 21:26:34 GMT -5
Bob..is that idocrase from pulga deposit
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Post by bobby1 on Feb 13, 2010 23:03:06 GMT -5
Rich, There is a small dark green spot on one side that didn't show in the photos so most likely it is a piece from Pulga. Bob
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