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Post by Jugglerguy on Aug 1, 2017 13:03:56 GMT -5
I do something similar to make beads, but in two dimensions. It works well for beads. Bead Jig
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notjustone
spending too much on rocks
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Post by notjustone on Aug 1, 2017 23:48:21 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: when you cut the top of the sphere would it not reduce diameter and drop farther into the socket as top cut part reaches bottom? then not cut on opposite side. you could probably get close by moving socket closer and removing tiny amounts per pass. but you will always be dropping into the socket with each pass.
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jamesp
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Post by jamesp on Aug 2, 2017 6:52:48 GMT -5
You may have to move the socket incrementally into the blade as sphere gets closer to round notjustone. The blade hits the sphere any where from 1/2 to 2/3's from the bottom of the sphere. So you are removing material off the side of the sphere. Regardless of where the blade is shaving the sphere, you must advance the socket closer to the blade as material is removed. Similar to the way Jugglerguy is advancing a bead into the saw blade as the cylinder forms and reduces in diameter. Great analogy for 2 dimensions. Sphere is 3 dimensions:
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notjustone
spending too much on rocks
Member since January 2017
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Post by notjustone on Aug 2, 2017 8:51:22 GMT -5
You may have to move the socket incrementally into the blade as sphere gets closer to round notjustone . The blade hits the sphere any where from 1/2 to 2/3's from the bottom of the sphere. So you are removing material off the side of the sphere. Regardless of where the blade is shaving the sphere, you must advance the socket closer to the blade as material is removed. Similar to the way Jugglerguy is advancing a bead into the saw blade as the cylinder forms and reduces in diameter. Great analogy for 2 dimensions. Sphere is 3 dimensions: yes but even when he advances bead in he is indexing off the center. your socket would be more like if he cut a notch in the board. once it cuts one side the ball is smaller and wont touch blade anymore. just like when you use a rip fence to make a cut then put cut side against fence its not going to cut second side because your already at the size from the first cut. like I said the shallower the cuts the closer you will be able to get to true round. your better bet would be to leave blade 90 degrees to socket clamp fixture so the center of socket is slightly less than diameter of ball from blade. plunge ball into side of blade till it falls into socket then spin horizontally. make a horizontally cut band around rock. turn ball slightly and make another cut repeat repeat repeat. as ball reduces in size and falls into socket it still stays centered same distance. and in contact with blade.
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jamesp
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Post by jamesp on Aug 2, 2017 10:39:28 GMT -5
You may have to move the socket incrementally into the blade as sphere gets closer to round notjustone . The blade hits the sphere any where from 1/2 to 2/3's from the bottom of the sphere. So you are removing material off the side of the sphere. Regardless of where the blade is shaving the sphere, you must advance the socket closer to the blade as material is removed. Similar to the way Jugglerguy is advancing a bead into the saw blade as the cylinder forms and reduces in diameter. Great analogy for 2 dimensions. Sphere is 3 dimensions: yes but even when he advances bead in he is indexing off the center. your socket would be more like if he cut a notch in the board. once it cuts one side the ball is smaller and wont touch blade anymore. just like when you use a rip fence to make a cut then put cut side against fence its not going to cut second side because your already at the size from the first cut. like I said the shallower the cuts the closer you will be able to get to true round. your better bet would be to leave blade 90 degrees to socket clamp fixture so the center of socket is slightly less than diameter of ball from blade. plunge ball into side of blade till it falls into socket then spin horizontally. make a horizontally cut band around rock. turn ball slightly and make another cut repeat repeat repeat. as ball reduces in size and falls into socket it still stays centered same distance. and in contact with blade. A band around it at a time eh ? I follow you. Band at 90 degrees to blade. Plunge in, rotate 360. Looks a plan. may take some iterations after that.
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Post by Jugglerguy on Aug 2, 2017 11:28:24 GMT -5
I got my bead idea from a woodworking video. I made plywood laps for my flat lap using the same method on my table saw. I just went searching for ideas on YouTube.
I swear I once saw a video of making a sphere on a table saw. I think the saw had a board above it with a hole in the board. The wooden cube was inserted into the hole and moved around so that all the parts that could reach the blade were removed. The finished ball will not fit through the hole, but will set in the hole with the bottom just touching the blade. Does that make sense. I haven't been able to find the video yet.
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jamesp
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Post by jamesp on Aug 3, 2017 7:42:38 GMT -5
Excellent Jugglerguy. The above concepts are realistic ways of cutting an agate sphere. Basic and do able. You do need to pass the rock by a high speed diamond blade in some form of a guide and jig just like you are doing with your bead jig. I will say that the tile saw rig with the Advanta blade has the capability of cutting a 2 to 2.5 inch sphere quickly. Even starting out with a rock that is not very close to a sphere.
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Post by Jugglerguy on Aug 3, 2017 9:22:04 GMT -5
That last video is what I was thinking of. I could have sworn I saw it done with a table saw. I think that if you set up something like his belt sander setup with your tile saw, it might work.
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jamesp
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Post by jamesp on Aug 3, 2017 11:31:51 GMT -5
The tile saw is easily the same as a table saw. Contemplation moving forward. Brian's scintillating... I agree, the last video solves the distance problem, is dead simple and easy to mount, and friendly for the tile saw blade. Plus it is safe. One 1.5 inch hole could do 2" to 3" spheres, just adjust the height above the blade. Oh yea. I could see it self propelling once you got close to a sphere. Best idea I ever have seen yet Jugglerguy. I must attempt.
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Post by Jugglerguy on Aug 3, 2017 11:59:50 GMT -5
The tile saw is easily the same as a table saw. Contemplation moving forward. Brian's scintillating... I agree, the last video solves the distance problem, is dead simple and easy to mount, and friendly for the tile saw blade. Plus it is safe. One 1.5 inch hole could do 2" to 3" spheres, just adjust the height above the blade. Oh yea. I could see it self propelling once you got close to a sphere. Best idea I ever have seen yet Jugglerguy. I must attempt. When you work out the bugs, I might give it a try too. Looks much simpler than making an egg!
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jamesp
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Post by jamesp on Aug 3, 2017 14:26:35 GMT -5
The tile saw is easily the same as a table saw. Contemplation moving forward. Brian's scintillating... I agree, the last video solves the distance problem, is dead simple and easy to mount, and friendly for the tile saw blade. Plus it is safe. One 1.5 inch hole could do 2" to 3" spheres, just adjust the height above the blade. Oh yea. I could see it self propelling once you got close to a sphere. Best idea I ever have seen yet Jugglerguy. I must attempt. When you work out the bugs, I might give it a try too. Looks much simpler than making an egg! egg would seem better on a lathe. Sphere looks easy with this rig you posted. Plus you have those round Great Lakes cobbles. Your unakite would be a good one.
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Post by Jugglerguy on Aug 3, 2017 14:35:48 GMT -5
When you work out the bugs, I might give it a try too. Looks much simpler than making an egg! egg would seem better on a lathe. Sphere looks easy with this rig you posted. Plus you have those round Great Lakes cobbles. Your unakite would be a good one. I just put a chunk of Kona dolomite in the saw in an attempt to cut a cube. I've never attempted a cube and the rock may be too big for the saw when I have to turn it. If it doesn't fit, I'll adjust it with an angle grinder. I figured I'd try a soft rock first. I worked out a formula for the size of the sphere, hole, and distance from the blade, at least I think I did. Here's what I have: x = radius of sphere y = radius of hole in board Distance from top of saw blade to top of board with hole in it = x - sqrt(x^2 - y^2)
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jamesp
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Post by jamesp on Aug 4, 2017 5:33:42 GMT -5
egg would seem better on a lathe. Sphere looks easy with this rig you posted. Plus you have those round Great Lakes cobbles. Your unakite would be a good one. I just put a chunk of Kona dolomite in the saw in an attempt to cut a cube. I've never attempted a cube and the rock may be too big for the saw when I have to turn it. If it doesn't fit, I'll adjust it with an angle grinder. I figured I'd try a soft rock first. I worked out a formula for the size of the sphere, hole, and distance from the blade, at least I think I did. Here's what I have: x = radius of sphere y = radius of hole in board Distance from top of saw blade to top of board with hole in it = x - sqrt(x^2 - y^2) Rob, engineer's apply formulas. Way to dumb to create formulas. Mathematician's derive formulas. Aren't you a math teacher ? The company I buy hemispherical steel bowls from gave me a similar challenge when he offered to cut 37.5 inch hemispheres down to a 'wok'(dome) shape. So after they stamp the plate they cut the excess away to a perfect 37.5 inch hemisphere which is 37.5/2 = 18.75 inches tall. Well, I have covers to fit over a 36 inch bowl, so I had to calculate the amount to cut off the 37.5 hemi to create a 36 inch diameter(dome). Apparently a slice off of a sphere is a 'dome'#$%^#@. So I had to go find a 'dome' formula %$#@&*. I hate sphere calculations %$#@&*. Any way, the answer was 6 inches...the result: From this 37.5 hemi To this 36 inch dome to fit cover as shown(The 36 inch Dome Fire Pit) Most of the 100 bowls: Well, I had to do a minimum order of 100 units(16,000 pounds) for the guy to set up the plasma cutter for the 6 inch removal cut, so the calculation HAD to be correct to come out to 36 inches. I also had him ship the 100 37.5 inch rings he cut off too, all together it about filled up a whole freight truck and was not cheap to ship from NE US. Ended up the (experimental) Dome fire pit has been a great seller. Sold 30 of 100 so far. Pay off for the 100 bowls started at after the 22nd fire pit sold. So I have 70 units left paid free and clear. Now, getting back to your dang formula, I see pieces of it in this formula. A derivation for the area of a dome I presume(cause I am lost) who does this stuff ?
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jamesp
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Post by jamesp on Aug 4, 2017 6:00:47 GMT -5
OK Rob, I forgot about a (crude) rig I made for the King Kong grinder that actually spit out two 1.5" spheres of your unakite, one of obsidian, and one of coral. It is very crude, but the hole allowed me to make several 1.5 inch spheres and made the task easy.(I was supposed to perfect this sphere thing but something came up). It is very similar to the jig in that last video you posted. The red plastic is a Walmart butcher block and is simply pinned at one corner. Can be lifted off/rotated to side. So different ones could be made with different sized holes. the hole was smaller when I made the 1.5 inch spheres: Your unakite Jugglerguy, ~1.5 inch. Tumbled Obsidian and a unakite after final grind A coral sphere None of them perfectly round, but they were shaped in a NOT-round hole. So lots of error. I never got around to cutting a perfect hole in the butcher block. Here is a link to the build and some of the rocks I ground and tumbled Nov. 2014. The diamond wheel is a Harbor Freight 7 inch diamond cup, $49. My business pulled me away from this project. I still have the grinding rig, must do further tinkering: www.flickr.com/photos/67205364@N06/sets/72157648700305650
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Post by Jugglerguy on Aug 4, 2017 21:06:23 GMT -5
Cool little spheres. I saw these at the time you made them, but I forgot all about them.
My cube turned out not that cube like. I was just eyeballing everything, so I guess my eyeballs are not that accurate. I was gone all day today, so there wasn't time to play.
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jamesp
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Post by jamesp on Aug 5, 2017 7:16:58 GMT -5
Cool little spheres. I saw these at the time you made them, but I forgot all about them. My cube turned out not that cube like. I was just eyeballing everything, so I guess my eyeballs are not that accurate. I was gone all day today, so there wasn't time to play. I never did cube anything. I tried to find close-to-round stones. Often cutting a roundish chunk off of a rock. Then freehand shaping. Freehand shaping off the edge of the wheel will get a ball park shape with out much effort. But does take the most time in the process. Your Great Lakes rocks make darn good near-to-sphere candidates. Of all the rocks I ever ground your unakite is solid and soft yet takes a polish in the tumbler. Grinds like a hard plastic, not glassy or brittle.
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Post by Jugglerguy on Aug 5, 2017 10:39:59 GMT -5
The belt sander method is seriously flawed. I've been thinking about this and it can't work the way I'd like it to work. My calculation was for a finished sphere. Those dimensions should work for a sphere. If you put a finished sphere over the hole, it should reach the saw blade (or belt sander). However, an unfinished sphere is larger and will not reach the blade. You'd have to start with a much larger hole and gradually decrease the diameter. The question is ,how do you know what to start decreasing the diameter? I'm not sure this is possible. There may be a very good reason that you never read anything about creating spheres this way.
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jamesp
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Post by jamesp on Aug 5, 2017 11:00:19 GMT -5
The belt sander method is seriously flawed. I've been thinking about this and it can't work the way I'd like it to work. My calculation was for a finished sphere. Those dimensions should work for a sphere. If you put a finished sphere over the hole, it should reach the saw blade (or belt sander). However, an unfinished sphere is larger and will not reach the blade. You'd have to start with a much larger hole and gradually decrease the diameter. The question is ,how do you know what to start decreasing the diameter? I'm not sure this is possible. There may be a very good reason that you never read anything about creating spheres this way. It is an iteration type process. Best if you had the socket on screw that could be lowered incrementally. I feel my crude spheres could have been dialed to a very accurate radius if I had a smooth plastic socket with a simple height adjustment. All you need is a fixed distance for the final grind. I would not change the hole, I would reduce the height gradually. pauls had his sphere within .002 inches using a divot in a board. I feel very confident this will work.
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notjustone
spending too much on rocks
Member since January 2017
Posts: 426
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Post by notjustone on Aug 5, 2017 11:24:14 GMT -5
The belt sander method is seriously flawed. I've been thinking about this and it can't work the way I'd like it to work. My calculation was for a finished sphere. Those dimensions should work for a sphere. If you put a finished sphere over the hole, it should reach the saw blade (or belt sander). However, an unfinished sphere is larger and will not reach the blade. You'd have to start with a much larger hole and gradually decrease the diameter. The question is ,how do you know what to start decreasing the diameter? I'm not sure this is possible. There may be a very good reason that you never read anything about creating spheres this way. in theory you would have to get the blade higher into the socket to get it to fall down into the socket. but as it cuts every time it falls in it gets a little deeper in the socket which makes blade cut again until ball is small enough to fall through. hence the socket next to blade set at 90 degrees doesn't have that problem. as it falls vertically into the socket the distance to blade and depth of cut doesn't change horizontally.
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notjustone
spending too much on rocks
Member since January 2017
Posts: 426
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Post by notjustone on Aug 5, 2017 11:28:24 GMT -5
The belt sander method is seriously flawed. I've been thinking about this and it can't work the way I'd like it to work. My calculation was for a finished sphere. Those dimensions should work for a sphere. If you put a finished sphere over the hole, it should reach the saw blade (or belt sander). However, an unfinished sphere is larger and will not reach the blade. You'd have to start with a much larger hole and gradually decrease the diameter. The question is ,how do you know what to start decreasing the diameter? I'm not sure this is possible. There may be a very good reason that you never read anything about creating spheres this way. It is an iteration type process. Best if you had the socket on screw that could be lowered incrementally. I feel my crude spheres could have been dialed to a very accurate radius if I had a smooth plastic socket with a simple height adjustment. All you need is a fixed distance for the final grind. I would not change the hole, I would reduce the height gradually. pauls had his sphere within .002 inches using a divot in a board. I feel very confident this will work. you would have to raise height as you progress because as the sphere gets smaller it would drop farther in the socket which would make it cut deeper on its own,
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