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 Nov 2, 2023 19:16:40 GMT -5
Got lucky at our local GemFair and found a vendor with obsidian rough.
Since the DIY toy motor saw is too slow and feeds too heavy, I built a new saw and cut an uneven obsidian preform.
If you’re interested, the new saw thread is here....
forum.rocktumblinghobby.com/thread/103836/diy-8
Round the sharp corners on a grinding wheel. Nail polish on the flats.
Toy motors work ok on the sphere machine.
Trying hole saws for roughing.
Not round yet. It is too big, and has lots of flats and flaws. Seems to take forever. I was too careless with the first roughing cuts so the rock is elongated a little. Not round enough, so touch-up grinding for the high spots. A lesson is to accurately cut the cube.
And It got stuck when I made coffee. Grinding for 10 minutes in one spot wore three grooves from the hole saws. Maybe too tight on grinding pressure. Measurements and hand grinding to fix it.
Almost round at ~3.0”.
As much as I want a flawless obsidian sphere, this one ain’t it. I overestimated the size of the sphere that lives in that rough, and cut it unevenly. Got flat spots, outer rind, and what looks like a butthole. Plaster to hold the rock means cutting blind. I need to saw more accurately. Maybe recut it to 2.5” tennis ball octahedron if I can hold onto it.
Tried some other grinding tools. Got milky water dripping off the ball, so it is grinding something. Using more grinding pressure. It would be a lot of hours to grind flaws ~1/4” deep. Seems like too much grinding to me. Places a premium on accurate sawing.
Core drill segments...
Also trying SiC grit cups and adding loose grit. These actually work, but they’re slow and need babysitting because they dry out. Only need a drop of water every few minutes and a pinch of fresh grit.
Also trying grinders made from acrylic display stands for baseballs. Bevel is a good fit. Glued on some diamonds. These will consistently grind 0.001” off the diameter per hour. Seems slow, especially for glass, but at least it’s measurable. Trying to increase it. Might make some new ones ground conformal to this rock with SiC loose grit, then glue on fresh diamonds.
Before, dry
After, scratched in a minute
Finer grit pads...
Pre polish & polish
My first obsidian sphere is 2.8”, and I learned a lot. Saw the preform accurately. Surface flaws are too deep to fix, and they detract from the sphere.
I’m starting to like the butthole now. Reminds me of South Park, where Cartman got a picture of Butters’ buttcheeks on milk cartons for missing kids, captioned “one brown eye”.
It was going to be named Planet Black Hole,
but now it’s Planet Butthole.
Or, if you prefer, Planet One Brown Eye.
Hope you like it. 
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Post by chris1956 on Nov 2, 2023 19:28:08 GMT -5
Looks pretty darn good to me. And thanks for the description of the process.
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RWA3006
Cave Dweller 
Member since March 2009
Posts: 4,625 
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Post by RWA3006 on Nov 2, 2023 20:08:00 GMT -5
Love it and enjoy the narrative. Informative too.
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Post by jasoninsd on Nov 2, 2023 20:24:25 GMT -5
Love your threads Rob! *...and love the name you picked for the "hole"! LOL |
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Post by hummingbirdstones on Nov 2, 2023 21:24:41 GMT -5
but now it’s Planet Butthole.  You're killing me! |
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jm
having dreams about rocks
Member since October 2015
Posts: 56
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Post by jm on Nov 3, 2023 2:06:20 GMT -5
I've been there more than once... the machine is running smooth, the sphere has good random rotation, everything looks good, so I step away for a couple minutes and come back to a sphere that's stuck in one spot with the grinding cups cutting circles into it.  That can be very aggravating. |
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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 Nov 3, 2023 20:42:59 GMT -5
I've been there more than once... the machine is running smooth, the sphere has good random rotation, everything looks good, so I step away for a couple minutes and come back to a sphere that's stuck in one spot with the grinding cups cutting circles into it. That can be very aggravating. Yes 'aggravating' is a good way to put it. I've felt that too. Also felt satisfaction at a task completed and man I hope this thing works. Even if it doesn't work at first.Maybe rockhounding leads me down a garden path to toy motors and drawer slides. There's a reason Highland Park doesn't do it this way. |
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wargrafix
Cave Dweller
Member since June 2023
Posts: 1,085
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Post by wargrafix on Dec 2, 2023 17:23:40 GMT -5
BUILD ME AN ARMY WORTH OF MOOORDDOOORRR
seriously, the flaw is the highlight. If a goddammn masterpiece
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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 Dec 5, 2023 0:56:54 GMT -5
BUILD ME AN ARMY WORTH OF MOOORDDOOORRR seriously, the flaw is the highlight. If a goddammn masterpiece Haha, yes. Planet Butthole has now earned a place on The Wall Of Shame! |
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wargrafix
Cave Dweller
Member since June 2023
Posts: 1,085
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Post by wargrafix on Dec 5, 2023 7:08:12 GMT -5
BUILD ME AN ARMY WORTH OF MOOORDDOOORRR seriously, the flaw is the highlight. If a goddammn masterpiece Haha, yes. Planet Butthole has now earned a place on The Wall Of Shame! I am awaiting an asteroid that looks exactly like this. Real life mimicking art. But seriously, you did great work |
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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 Jun 17, 2024 22:22:36 GMT -5
It''s just a lot of work for one joke. |
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Post by Rockoonz on Jun 18, 2024 0:35:56 GMT -5
Planet bunghole?  |
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JR8675309
freely admits to licking rocks
Member since August 2019
Posts: 807
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Post by JR8675309 on Jun 19, 2024 21:52:08 GMT -5
Eye of Sauron for surrree
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Post by 1dave on Jun 21, 2024 9:55:11 GMT -5
A lot of work, a lot of learning.
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Post by pauls on Jun 24, 2024 20:02:54 GMT -5
I liked your description of the process,
I made my first sphere 60 years ago, I was 13, It was 3" as well, had to be, I only had a 10" saw so that was the biggest I could saw. Completely manual one cup on the end of my sander arbor and another cup in hand, It came out really well, the sphere is only 2 thou out of round. Best in show at the clubs very first exhibition.
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Post by tribeunited on Jun 26, 2024 15:45:41 GMT -5
This is one of the coolest threads I've read. I said one of them, no hurt feelings everyone else!
For real though, it's awesome you're able to do so much! You had me thinking I could do it until the welding started (in the making the saw part) That's when I said, "Yeah, probably not."
I bought a welder because I wanted to weld. That and I love tools, a lot. I haven't tried welding anything yet, I just took it out of the box, set it up, and pulled the trigger while I laughed like a crazy person.
Back to you. Thanks for creating this super informative and inspiring post!
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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 Jul 2, 2024 16:43:07 GMT -5
I liked your description of the process, I made my first sphere 60 years ago, I was 13, It was 3" as well, had to be, I only had a 10" saw so that was the biggest I could saw. Completely manual one cup on the end of my sander arbor and another cup in hand, It came out really well, the sphere is only 2 thou out of round. Best in show at the clubs very first exhibition. As a machinist I'm ok using measuring tools. Problem is my Mitutoyo 6" calipers only have ~1.5 throat depth. Can't measure to the equator of a >3" planet. So I got feeler calipers.  www.amazon.com/dp/B077XK2XWL?ref=ppx_yo2ov_dt_b_product_details&th=1It's kinda sketchy to "feel" the diameter of the sphere, and sketchy to "feel" the Mitutoyos on the feeler calipers, but it works. So I wonder how everybody measures roundness. And congrats on Best In Show! |
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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 Jul 2, 2024 17:01:04 GMT -5
This is one of the coolest threads I've read. I said one of them, no hurt feelings everyone else! For real though, it's awesome you're able to do so much! You had me thinking I could do it until the welding started (in the making the saw part) That's when I said, "Yeah, probably not." I bought a welder because I wanted to weld. That and I love tools, a lot. I haven't tried welding anything yet, I just took it out of the box, set it up, and pulled the trigger while I laughed like a crazy person. Back to you. Thanks for creating this super informative and inspiring post! No welding to make the saw or the sphere machine. I've done brazing, stick weld, and TIG, but don't have the tools now. So the saw is made like Legos or Tinkertoys - no welds, just drill holes and screw it together. Glad you liked it. I covet your welder. |
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Post by Rockoonz on Jul 3, 2024 2:03:03 GMT -5
I liked your description of the process, I made my first sphere 60 years ago, I was 13, It was 3" as well, had to be, I only had a 10" saw so that was the biggest I could saw. Completely manual one cup on the end of my sander arbor and another cup in hand, It came out really well, the sphere is only 2 thou out of round. Best in show at the clubs very first exhibition. As a machinist I'm ok using measuring tools. Problem is my Mitutoyo 6" calipers only have ~1.5 throat depth. Can't measure to the equator of a >3" planet. So I got feeler calipers. www.amazon.com/dp/B077XK2XWL?ref=ppx_yo2ov_dt_b_product_details&th=1It's kinda sketchy to "feel" the diameter of the sphere, and sketchy to "feel" the Mitutoyos on the feeler calipers, but it works. So I wonder how everybody measures roundness. And congrats on Best In Show! I used a height gauge. |
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Post by pauls on Jul 3, 2024 4:11:28 GMT -5
"So I wonder how everybody measures roundness."
In my case my dad was a machinist too, he worked at a Government power station so had access to the best measuring tools money could buy, I'm not sure exactly what he used to measure it but I know he had a set of quite large micrometers, I scored some of them when the station was closed down and they sold off everything. I will never use some of that stuff but it's cool to have a nice instrument cupboard set up in my workshop. I am at best a mug machinist, but it's enough to get me out of trouble sometimes.
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You're killing me!
That can be very aggravating. 
