kevin24018
spending too much on rocks
Member since February 2012
Posts: 284
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Post by kevin24018 on Jul 31, 2017 9:04:45 GMT -5
After seeing the articles about preforming with various 'super grinders' and even making a sphere with a hand grinder I was wondering, if you ground a rock to a basic sphere shape and tumbled it, would that work?
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Post by manofglass on Jul 31, 2017 9:14:32 GMT -5
It may go out of round a little but it will roll Try it see what you get
Walt
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Post by captbob on Jul 31, 2017 9:17:34 GMT -5
I believe that jamesp did something along those lines. Not sure that I recall seeing his results (so many experiments!) maybe he will chime in here.
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Fossilman
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Post by Fossilman on Jul 31, 2017 9:20:13 GMT -5
Yes sir James has done this....
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jamesp
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Post by jamesp on Jul 31, 2017 10:11:07 GMT -5
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kevin24018
spending too much on rocks
Member since February 2012
Posts: 284
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Post by kevin24018 on Jul 31, 2017 10:52:20 GMT -5
I'm guessing a rotary wouldn't work too well.
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notjustone
spending too much on rocks
Member since January 2017
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Post by notjustone on Jul 31, 2017 10:53:45 GMT -5
yes but not perfect sheres like you get off the shere machines. I call them "nearspheres". but I have been toying with the idea of making a sphere grinder to do rough grind then into tumblers to finish.
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Sabre52
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Me and my gal, Rosie
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Post by Sabre52 on Jul 31, 2017 10:56:56 GMT -5
Yep, vibe tumbler in last stages would change the shape very little. Would have to be pretty round going in though. I'd think a rotary tumbler would deform the sphere too much. I've seen some nice marbles finished in a vibe....Mel
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kevin24018
spending too much on rocks
Member since February 2012
Posts: 284
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Post by kevin24018 on Jul 31, 2017 11:04:56 GMT -5
yes but not perfect sheres like you get off the shere machines. I call them "nearspheres". but I have been toying with the idea of making a sphere grinder to do rough grind then into tumblers to finish. that was kind of my thought as well.
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notjustone
spending too much on rocks
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Post by notjustone on Jul 31, 2017 11:07:32 GMT -5
I'm still waiting to see the nearshere polished.
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jamesp
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Post by jamesp on Jul 31, 2017 11:17:12 GMT -5
I used a rotary to remove the grind marks from pre-grinding. If you shape it well on the pre-grinder it only takes a few days for the rotary to remove the grind marks. The sphere is only as good as you grind it on the pre-grinder. Plain and simple. Rotary does do a good job removing material and grind marks consistently and does not seem to alter the spherical or discoidal's shape if rock has no soft spots. The vibe does not alter the shape, just lays a polish down. Need to go finish the discoidal and the sphere. Tumblers have been shut down. However, with the new tile saw rig I might be able to use a jig to get a realsphere instead of a nearsphere. That tile saw would spit out 2 to 2.5 inch spheres from Mohs 7 cobbles in a jiffy IF I had a jig. Need a machinist( notjustone). I may be able to handle the building of the jig. It is on the bucket list. it would be like 2 rolling shafts to rotate the rock on as it is held against the diamond wheel. Something like this notjustone that holds the stone and allows a man to rotate the stone by hand against the high speed diamond wheel to get a fixed radius.
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Post by pauls on Jul 31, 2017 16:39:37 GMT -5
James. I did much the same as you are thinking with my first sphere. I built a fixed platform that went in front of the grinding wheel, much like a rest, I ground a small indentation in it so the sphere was sitting in it at the right distance and moved the rock around by hand. Very Heath Robinson but it worked, it was 50 years ago and I was 16 at the time.
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Deleted
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Post by Deleted on Jul 31, 2017 17:04:12 GMT -5
I have been considering taking a machine perfect sphere and doing final steps in a vibe.
No results. Just ideas
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notjustone
spending too much on rocks
Member since January 2017
Posts: 426
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Post by notjustone on Jul 31, 2017 22:56:12 GMT -5
I used a rotary to remove the grind marks from pre-grinding. If you shape it well on the pre-grinder it only takes a few days for the rotary to remove the grind marks. The sphere is only as good as you grind it on the pre-grinder. Plain and simple. Rotary does do a good job removing material and grind marks consistently and does not seem to alter the spherical or discoidal's shape if rock has no soft spots. The vibe does not alter the shape, just lays a polish down. Need to go finish the discoidal and the sphere. Tumblers have been shut down. However, with the new tile saw rig I might be able to use a jig to get a realsphere instead of a nearsphere. That tile saw would spit out 2 to 2.5 inch spheres from Mohs 7 cobbles in a jiffy IF I had a jig. Need a machinist( notjustone ). I may be able to handle the building of the jig. It is on the bucket list. it would be like 2 rolling shafts to rotate the rock on as it is held against the diamond wheel. Something like this notjustone that holds the stone and allows a man to rotate the stone by hand against the high speed diamond wheel to get a fixed radius. I'm not a machinist. I'm a machine repair mechanic.
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jamesp
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Post by jamesp on Aug 1, 2017 2:33:35 GMT -5
James. I did much the same as you are thinking with my first sphere. I built a fixed platform that went in front of the grinding wheel, much like a rest, I ground a small indentation in it so the sphere was sitting in it at the right distance and moved the rock around by hand. Very Heath Robinson but it worked, it was 50 years ago and I was 16 at the time. Now that sounds like a plan pauls. THAT is a forward movement. 1 inch butcher block nylon with a partial sphere(socket) cut in it(defined a dome). Low friction, can hold some drip water, allow rotation. Holds it at a constant radius. Rough by hand, final using slick spherical socket. That may be all that is needed. As it is I turn the tile saw table blade at 45 degrees and roll the stone against the tile saw table and the edge of the slanted blade. That serves as a good guide for rough radius grinding. If the table had a spherical socket to serve as a guide I'm certain of perfect spheres. 1.5", 2", 2.5", 3" holes could be cut into nylon butcher block with forstner bit and chamfered by hand with a file to serve as a socket. Best if it could be on an adjustable feed screw and slight fixed adjustments from blade could be made. Made a nearsphere without a socket on the tile saw table by resting the rock on the flat table and rotating by hand against slanted blade. Given that socket in a fixed spot the sphere likely would have been perfect. Make different sockets for different size spheres. Move socket slightly closer to blade as sphere is grinding to a perfect sphere. Keeps it simple. My 3 attempts at making shapes with super shaper tile saw grinder free hand: www.flickr.com/photos/67205364@N06/albums/72157683648790962Don't be fooled by this little tile saw grinder, at 3600 RPM and a dead smooth rotation it is a real Mohs 7 rock eater. Blade very important- 7" Advanta tuck blade, $27 Ebay. Note: Tile saw can be laid down flat and blade bottom kept in water tray. It is the table top that flips up, not the saw blade. Position of saw was ergonomic choice. This would allow adjustment of rock socket from blade:
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Post by pauls on Aug 1, 2017 3:50:36 GMT -5
Sounds about right James. Mine started out as just a rest in front of the wheel (silicon carbide) so pretty quickly the grit wore the perfect indentation in the softwood rest (told you it was Heath Robinson) and it worked perfectly. The final sphere was only .002 inch out of perfect round and thats probably because of a slightly softer spot in the stone. Not too bad for a fifteen year old kid.
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jamesp
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Post by jamesp on Aug 1, 2017 4:21:21 GMT -5
Sounds about right James. Mine started out as just a rest in front of the wheel (silicon carbide) so pretty quickly the grit wore the perfect indentation in the softwood rest (told you it was Heath Robinson) and it worked perfectly. The final sphere was only .002 inch out of perfect round and thats probably because of a slightly softer spot in the stone. Not too bad for a fifteen year old kid. .002 Wow. And you used SiC wheel. This socket thing did pass through my mind when using the flat table as a fence rest for free hand shaping. The socket can be moved at different points along the arc of the blade to mate to various size spheres. The socket gives three dimensions of control, plain and simple. Heath Robinson and Ruth Goldberg can be very good friends.
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jamesp
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Post by jamesp on Aug 1, 2017 4:25:46 GMT -5
Advanta 7" tuck blades, 1/4" thick, 5 pack, $110 ppd. I did this deal. That is $20 each and will grind a bunch of rocks before wearing out. Many moons of grinding. www.ebay.com/itm/5PK-7-x-250-Tuck-Point-Diamond-Blade-for-Mortar-Concrete-Masonry-/132036872268?hash=item1ebe02c84c:g:s8gAAOSw-0xYVJSrI retired the King Kong grinder and use the tile saw super shaper. It's all about the 3600 RPM and smooth operation of the tile saw motor. The shaft on the tile saw motor is made for a tight fit on tile and tuck blades for perfect concentricity. Important. The King Kong was underpowered at 1/4 HP. Most tile saw motors are 1/2 HP. So very powerful. Sharp Advanta blades work well with lower horsepower, pushing rock against blade with lots of pressure is unnecessary due to their sharp diamonds. In the event the blade gets out of round it is a $20 loss. Never happened on the tile saw, but is a regular occurrence on the out-of-round King Kong grinder. Be it diamond cup, tuck blade, stack of tile saw blades. Once they get out of round the rock bounces against the hard blade and grinding becomes a miserable task. They may make a diamond wheel dressing tool for diamond wheels, do not know. They do make wheel dressers out of diamond for AO and SiC wheels - different animal.
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kevin24018
spending too much on rocks
Member since February 2012
Posts: 284
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Post by kevin24018 on Aug 1, 2017 7:21:50 GMT -5
James. I did much the same as you are thinking with my first sphere. I built a fixed platform that went in front of the grinding wheel, much like a rest, I ground a small indentation in it so the sphere was sitting in it at the right distance and moved the rock around by hand. Very Heath Robinson but it worked, it was 50 years ago and I was 16 at the time. Now that sounds like a plan pauls. THAT is a forward movement. 1 inch butcher block nylon with a partial sphere(socket) cut in it(defined a dome). Low friction, can hold some drip water, allow rotation. Holds it at a constant radius. Rough by hand, final using slick spherical socket. That may be all that is needed. As it is I turn the tile saw table blade at 45 degrees and roll the stone against the tile saw table and the edge of the slanted blade. That serves as a good guide for rough radius grinding. If the table had a spherical socket to serve as a guide I'm certain of perfect spheres. 1.5", 2", 2.5", 3" holes could be cut into nylon butcher block with forstner bit and chamfered by hand with a file to serve as a socket. Best if it could be on an adjustable feed screw and slight fixed adjustments from blade could be made. Made a nearsphere without a socket on the tile saw table by resting the rock on the flat table and rotating by hand against slanted blade. Given that socket in a fixed spot the sphere likely would have been perfect. Make different sockets for different size spheres. Move socket slightly closer to blade as sphere is grinding to a perfect sphere. Keeps it simple. My 3 attempts at making shapes with super shaper tile saw grinder free hand: www.flickr.com/photos/67205364@N06/albums/72157683648790962Don't be fooled by this little tile saw grinder, at 3600 RPM and a dead smooth rotation it is a real Mohs 7 rock eater. Blade very important- 7" Advanta tuck blade, $27 Ebay. Note: Tile saw can be laid down flat and blade bottom kept in water tray. It is the table top that flips up, not the saw blade. Position of saw was ergonomic choice. This would allow adjustment of rock socket from blade: brilliant and simple design, all you need is a jig to keep the rock a certain distance away and just rotate it
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jamesp
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Post by jamesp on Aug 1, 2017 12:03:39 GMT -5
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