Steve
has rocks in the head
Member since June 2005
Posts: 506
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Post by Steve on Aug 4, 2012 12:16:21 GMT -5
Here's a couple of spheres that I just finished polishing. The first is Alaskan Jade with a diameter of 3.75 inches. The second is Kaleidoscope Jasper with a diameter of 3.71 inches.
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Post by jakesrocks on Aug 4, 2012 12:28:47 GMT -5
Very nice. One of these days I'll find the time to finish my sphere machine build.
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jason12x12
freely admits to licking rocks
Member since October 2011
Posts: 798
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Post by jason12x12 on Aug 4, 2012 13:14:31 GMT -5
those are great.. been a really long time since ive seen anything like that on here ..Question/ how long does it take to make those start to finish?
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Post by jakesrocks on Aug 4, 2012 13:32:10 GMT -5
On my small machine, start to finish is less than a day for a 1" sphere. It'll take a little bit longer for a larger one if you're using standard cups with SC. Should be quicker with diamond cups.
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Steve
has rocks in the head
Member since June 2005
Posts: 506
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Post by Steve on Aug 4, 2012 17:34:34 GMT -5
Jason: Start to finish - it's hard to say or quantify how long it takes.
First you have to cut the preform. This takes a min of 26 cuts - first 6 to cut out a cube, then 4 to make an octagon pillar, then 8 cuts at each end. Next you should grind down the edges a bit - I must admit that I generally skip this step, which adds to the grinding time.
I use silicon carbide to grind the preform into a sphere. It would be much faster to use diamond cutting cups, but I can't afford the initial investment - over the long run diamond will pay for itself - you can't believe how much course grit a sphere machine uses and wastes. Sometimes I use the rock slurry from the sphere machine as the rough grit for the tumbler.
The time to grind the preform into a sphere is highly variable - it depends on the hardness of the rock, how good of a job I did on making the preform, and how carefully I monitor the machine keeping it at it's most efficient. I've had preforms go totally round in an hour and a half - soft serpentine and calcite - and I've had to spend over a week grinding 12 hours a day - very hard agate with deep low spots, otherwise known as flat spots (i.e. didn't do a good job with the preform). Also my machine is a homemade that's not very efficient.
Then you're ready to sand and polish. I now use diamond pads for this. However the machine must be perfectly clean. After a couple of bad experiences I've learned to take off the motors and other electrical parts and to power wash the machine. Then I repaint it. So I grind a bunch of spheres and then convert the machine to polish mode. Except for glass and obsidian I can sand and polish several spheres in a few hours. I can't get a good polish on glass or obsidian (and some other softer materials) with diamond so it takes an extra day with tin oxide on leather for these.
I'm not very productive, this is really just a weekend and summer time hobby for me, so it usually takes me about a year to get a sphere, start to finish, but then I get a batch of them. I'm in the process of rebuilding a second garage sale homebuilt sphere machine, so I hope to be able to start skipping the power wash and repaint step.
The smallest sphere I can make is a bit over 2 inches, the largest is about six inches. The machine is happiest at 3 - 4 inches. I often think about trying to put together a smaller machine to make large marble size spheres.
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jason12x12
freely admits to licking rocks
Member since October 2011
Posts: 798
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Post by jason12x12 on Aug 4, 2012 18:55:50 GMT -5
I remember your build pics i think... show some of the smaller one you build. when you build it. i will be interested to try as well
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Post by Bikerrandy on Aug 5, 2012 8:48:46 GMT -5
Those are pretty, I like the second one best I think. Cool stuff!!
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Post by 3rdrockfromthefun on Aug 5, 2012 9:11:10 GMT -5
Nice! And I had no idea how much time and work went into those!
Someone needs to invent a sphere prepping saw!
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Steve
has rocks in the head
Member since June 2005
Posts: 506
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Post by Steve on Aug 5, 2012 17:48:30 GMT -5
I've seen pictures of one (sphere preform machine). In fact a picture of one was posted on this forum a couple of years ago. Most of the big time sphere makers use a core drill to make their preforms.
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Deleted
Deleted Member
Member since January 1970
Posts: 0
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Post by Deleted on Aug 5, 2012 22:39:33 GMT -5
Hi Steve,
Those are some nice looking spheres. You should try the diamond brazing rod from Sphereheaven.com, dedicate a set of cups for 40/60 grit and you will be surprised how much time it saves.
Tim
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juzwuz
has rocks in the head
Member since April 2010
Posts: 526
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Post by juzwuz on Aug 7, 2012 14:10:47 GMT -5
Nice! I'm still trying to figure out how to polish obsidian spheres. I tried 14k diamond paste on leather but it didn't seem to get a great polish. For grinding I've been using diamond core drill bits which have worked OK. I'm trying HP Lapidary's sphere cups right now and some time in the future, I might try the diamond brazing rods.
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Deleted
Deleted Member
Member since January 1970
Posts: 0
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Post by Deleted on Aug 7, 2012 15:05:08 GMT -5
Justin, we do obsidian spheres at our class with PVC cups. We take a square of denim (old levi's I am sure) and on top of that a square of "polishing cloth" from the automotive store. The fabric squares are then rubber banded over the PVC cups. Final polish is 30 minutes with Tin Oxide.
These shine like factory new!
I'll finish BLue G tonight (hopefully) and then do two Llanite ones. Then I think I'll do obsidian. Probably in late September! lol
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