jamesp
Cave Dweller
Member since October 2012
Posts: 36,561
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Post by jamesp on Sept 18, 2016 14:51:18 GMT -5
This grinds fast since it is soft. Theory is that if it is the only big rock in the tumbler it should escape frosting so common with obsidian(damn it). Note to self, when doing coarse grind on large rocks in rotary use softer glass for media so grit will not break down so fast and last longer. Rough: After grinding, dry: After grinding, wet:
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Post by captbob on Sept 18, 2016 15:17:29 GMT -5
You are the busiest person I know.
Looking forward to progress reports.
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,561
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Post by jamesp on Sept 18, 2016 15:25:22 GMT -5
You are the busiest person I know. Looking forward to progress reports. Building PVC barrels yesterday-yes busy, easier to weld 10 fire pits. Grinding that obsidian kanockulator was easy. Rudely chunked n the rotary and walked away.
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Post by HankRocks on Sept 18, 2016 16:24:02 GMT -5
I assume you are removing any non-exposed surfaces, or recesses, with all the grinding. What wheel are you using to do this grinding? and how long is it taking?
As the previous post mentioned, you are one busy fellow, which is good by me.
Thanks
H
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,561
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Post by jamesp on Sept 18, 2016 17:25:19 GMT -5
I assume you are removing any non-exposed surfaces, or recesses, with all the grinding. What wheel are you using to do this grinding? and how long is it taking? As the previous post mentioned, you are one busy fellow, which is good by me. Thanks H Exactly Hank, just what you said add some rounding/shaping. This is the old 4 inch diamond cup, now using 7 inch. Both from Harbor Freight turning 2200 RPM. They are ~30-40 grit. ah, welcome to forum.
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Post by HankRocks on Sept 18, 2016 19:06:16 GMT -5
Wow! That's a very fast grind. It does generate a lot of dust, hope you taking some precaution against breathing it. And watch those fingers!!
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,561
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Post by jamesp on Sept 19, 2016 1:02:43 GMT -5
Wow! That's a very fast grind. It does generate a lot of dust, hope you taking some precaution against breathing it. And watch those fingers!! A guard has been secured Hank. Ventilation provided by 1/2 hp squirrel cage and 1/2 hp 42 inch greenhouse fan in series. Total evacuation.
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,561
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Post by jamesp on Sept 19, 2016 1:50:29 GMT -5
This setup uses a 1/4 HP motor driving wheel at 2200 RPM. Wheel is slowing down on these large rocks. Grinding large rocks would be best with 1/2 to 1 HP motor on this set up. Diamond cup wheel designed for 5000 RPM with 2-3 HP motors and much more pressure than I am applying.
Am looking for a 7 or 9 inch diamond cup with continuos wider diamond zone.
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,561
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Post by jamesp on Sept 19, 2016 4:59:31 GMT -5
Will have to try coarse grinding obsidian with broken up alum ox grinding wheels. Broken in one inch chunks it should cut a big chunk of obsidian up like butter. The big heavy rock grinds fast. Lots of weight bearing down it at all times in the tumbler because of it's weight. More so than little one inch rocks. Big rock = fast tumble. Fast tumble = good.
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,561
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Post by jamesp on Sept 19, 2016 7:01:57 GMT -5
Am pumped about doing these large single rocks. Presently building 5-7 six pound capacity extra heavy duty PVC barrels just for doing big rocks one per barrel. The media is simply regular tumbles during coarse grind. They end up being tumbles too. Gotta find a 'continuous' diamond cup wheel with bigger diamond face surface. Like this: Not like this:
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,561
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Post by jamesp on Sept 19, 2016 7:05:31 GMT -5
Found a 7 inch continuous wheel with diamonds 10mm thick, incredible. But have to but a lot of 100(China)(Alibaba). Still shopping.
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,561
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Post by jamesp on Sept 22, 2016 10:39:23 GMT -5
After 24 hours in the vibe with sugar and AO 80 a slight polish is already forming. This chunk of snowflake is a low grade chunk with lots of soft spots and pits. Regardless, I hope to get a decent polish on it. If it does, the method being used should do great on a single large quality stone with pea sized media. And darn fast. 1 pound 8 ounces
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