callmerob
starting to spend too much on rocks
I really like a dirt road
Member since September 2019
Posts: 143
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Post by callmerob on Aug 3, 2021 0:44:56 GMT -5
A small geode... A couple of years ago, in The Before Times, we went to our local Gem Fair / Rock Show / Craft Fair. Met my new best friend Joba from East Africa. Joba is everybody’s new best friend. He had outdoor tables with rocks, and his Lady had African fabrics - beautiful stuff. I sorted through a 5-gallon bucket of whole, small, cheap geodes to find the ones that were the most round. The best I could find was a 2" dirty mud ball with lumps and a squished flat spot. It’ll never be a round sphere, but it might clean up a little. It is also very light, and initial hand grinding to prep it for the sphere machine opened a tiny hole in one end, so I stopped grinding.  Tried diamond hole saws for kitchen countertops, and they worked ok to knock the mud off, but they seemed pretty ineffective when it got down to the quartz veins. Maybe I was too impatient.  Tried diamond impregnated plastic grinding discs, but their flat shape means little area contact with the rock. Also using generous lay-back angle on the discs because more vertical discs don’t hold the rock when it hits the flat spot. It squirts up or down and out. Again, impatient.  Tried my water bottle cap grinding cups with SiC grit and super glue, but they are too small and the rock wouldn’t roll. Kept getting stuck on the lumps. So I made some larger grinding cups from juice bottle caps. 1.5” diameter bottle caps, one teaspoon SiC grit, super glue, 2” backing pads. And they worked better.  I’m alternating with 3 other Joba geodes when I get tired of watching this one. Two of them are very heavy, probably no cavity, but with quartz veins and some very tough basalt under the mud ball. They are slow-going too, so I'm focusing on this one rock. Using only light grinding pressure because I’m afraid of breaking it before it gets smoother, and heavier pressure results in it getting stuck on the flat spot. Finally the cavity opens up a little at a time to reveal the inside.  I don’t know the origin of this rock, but I like to think that Joba brought it for me from the Great Rift Valley in East Africa. I like how the quartz veins form the structural ribs for the cavity. And that we are the first to see into this crystal cave.  At night, on a red flashlight...  Devil's playground...  Hope you like it.  |
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Post by jasoninsd on Aug 3, 2021 2:29:56 GMT -5
Rob, you are definitely resilient and ingenious! I love it! I thought taking up certain aspects of this hobby would teach me to have better patience...but I think it just makes my own impatience worse! So, don't feel all alone with regards to that! LOL |
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callmerob
starting to spend too much on rocks
I really like a dirt road
Member since September 2019
Posts: 143
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Post by callmerob on Aug 3, 2021 3:35:59 GMT -5
jasoninsd, Yep LOL. I'm starting to think of the sphere machine as less of a grinder, and more of a tumbler. You know, the kind where you push the button and don't see any results for two weeks. It's teaching me patience. And patience is a virtue. |
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Brian
fully equipped rock polisher
Member since July 2020
Posts: 1,512
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Post by Brian on Aug 3, 2021 8:06:28 GMT -5
The cap idea really seems to work well. If it gets too much bigger, you’ll be using peanut butter jar lids.
I wonder how well 3D printed cups would work. PLA is the most common material, but I know that other materials are possible, and there are companies that can print in many different materials. It may not be cost effective, but definitely worth considering. It may even be possible to print a cup to accept diamond segments that can be replaced as needed.
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callmerob
starting to spend too much on rocks
I really like a dirt road
Member since September 2019
Posts: 143
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Post by callmerob on Aug 3, 2021 22:11:49 GMT -5
Brian, Ooooh! I like the 3D printed idea! Maybe with base mounting threads included. And stiffening ribs to save materials. My brother "knows a guy". I'll ask him. Thanks! |
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Brian
fully equipped rock polisher
Member since July 2020
Posts: 1,512
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Post by Brian on Aug 4, 2021 8:23:47 GMT -5
Brian, Ooooh! I like the 3D printed idea! Maybe with base mounting threads included. And stiffening ribs to save materials. My brother "knows a guy". I'll ask him. Thanks! Let me know what he says! There’s a company called Shapeways that will 3D print in 75 different materials, including stainless steel and brass, but I’d be more curious if the PLA that home 3D printers use would be strong enough to hold up in a cost effective manner. I’d like to think it could based on the fact that your bottle caps work well. Grit would be fine to use because it’s cheap but if sockets for diamond segments could be incorporated, then even better. |
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callmerob
starting to spend too much on rocks
I really like a dirt road
Member since September 2019
Posts: 143
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Post by callmerob on Aug 4, 2021 13:25:59 GMT -5
Brian, Yes I've seen Shapeways. Thanks for the recommendation. I'd probably try the cheapest plastic first. I'm learning that my grit cups work better than flat stuff, so I'm messing around with ideas to make solid cups for diamond segment discs. Looked at the PVC cups on Sphere Heaven, but don't like the cost, or the big clunky pipe threads, or the Bondo to make the cup shape. Being such a rookie can be fun. Stumbling around in the dark, reinventing the wheel. |
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callmerob
starting to spend too much on rocks
I really like a dirt road
Member since September 2019
Posts: 143
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Post by callmerob on Aug 6, 2021 11:58:55 GMT -5
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NDK
Cave Dweller 
Member since January 2009
Posts: 9,440
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Post by NDK on Aug 9, 2021 19:14:31 GMT -5
That's a cool geode sphere Rob!
Love the story too. Was fun to read.
One of these days I'll get to our sphere machine and get some pix up.
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Post by DirtCleaner on Aug 23, 2021 9:14:49 GMT -5
This was my first attempt at polishing. The flat pads will never work. They need to be concave.
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Post by DirtCleaner on Aug 23, 2021 9:17:20 GMT -5
Here is one method of making polishing cups. If you don't have access to a lathe use PVC cups. You can either use a Dremel tool or some other type to bevel the cups a bit. Or just simply use lots of glue and place the pads on in a concave shape.
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callmerob
starting to spend too much on rocks
I really like a dirt road
Member since September 2019
Posts: 143
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Post by callmerob on Aug 23, 2021 11:45:35 GMT -5
Here is one method of making polishing cups. If you don't have access to a lathe use PVC cups. You can either use a Dremel tool or some other type to bevel the cups a bit. Or just simply use lots of glue and place the pads on in a concave shape. Thank you for taking the time to share this information - very helpful. Through trial and error, I've concluded much the same. Now having fun messing around with PVC and the diamond pads. It's very helpful to see how you did it. I'm envious of your workshop and that classic South Bend lathe. Very much enjoyed your videos. |
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