Saskrock
fully equipped rock polisher
Member since October 2007
Posts: 1,852
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Post by Saskrock on Dec 12, 2007 12:37:35 GMT -5
I had an idea that I could take my sphere maker and attach on a flat plate to the threaded shaft,that is covered with rubber with a lip around it like so. then I am thinking I could put in some grit and water, drop a slab or cut geode in and let it spin away to polish or at least grind smooth on its own. I will also have to put in a blocker of some kind to keep things from just going in circles. So here is where I need help. Unless I am wrong I think the grit will end up at the outside edge and stay there because of centrifugal force. Does anyone have any ideas??
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SirRoxalot
freely admits to licking rocks
Member since October 2003
Posts: 790
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Post by SirRoxalot on Dec 13, 2007 11:55:47 GMT -5
Examine some flat laps at a rock shop to see how they're built. Doesn't the polishing face have some sort of thick felt on it to hold the grit? I thought they were mostly vibratory? What would hold your rocks in place instead of going around merrily with the wheel?
SirRoxalot
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Post by johnjsgems on Dec 13, 2007 20:36:33 GMT -5
What you have is the potential for a conventional lap. Generally the lap plate is flat and grooved. You dampen and sprinkle with grit. You hold the rock by hand on the lap. You can feel it pull when too dry and hear it cutting (or not) to know when to add grit. You have to clean the plate really well between steps I saw a homemade lapper recently "Minnesota Bob" the fossil algae guy makes. He has an overhead holder for the rocks and a rotating plate with a hardwood floor sanding disc. Uses it dry and they come out really nice. It may have been a rotating overhead rock and a fixed plate with disc but either way would work. Your lap will have to turn pretty slow and be ground flat. They also make magnetic diamond laps that work really fast and cost a lot too. You won't be able to make a vibrating lap out of your unit.
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Saskrock
fully equipped rock polisher
Member since October 2007
Posts: 1,852
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Post by Saskrock on Dec 14, 2007 0:25:35 GMT -5
Unfortunately I live about 12 hrs from the nearest rock shop, with no local club or even anyone else who collects rocks . So checking something else out is pretty much out. Don't Suppose anyone has a picture? The grooved plate idea is interesting, could you give me a little more info on how it works? Are the grooves like one of these? And how many RPM does a flat lap spin at?? I'm still not sure what would keep the grit on the plate unless it is going really slow? Thanks
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Post by johnjsgems on Dec 14, 2007 1:27:30 GMT -5
If you go to Diamond Pacific's website look at their Rotating Disc Flat Lap on page 21 of their online catalog. There is a good picture of the unit and the lap plate. They don't say what rpm.
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Saskrock
fully equipped rock polisher
Member since October 2007
Posts: 1,852
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Post by Saskrock on Dec 14, 2007 11:03:39 GMT -5
Thanks for the site John. I guess it just shows what a newbie I am to this hobby. I didn't even know until I saw that picture that I have apparently pretty much built a flat lap ;D So it looks to me that the grooves just slow the grit down so it doesn't come off immediately. Then the drip can either drips a grit/water mix from the drip can to replace it. Or that you use just water in the can but not much flow so it just wets the grit so you get more of a paste that just sticks on a bit so it stays on. So unless I'm completely off the mark all I need now is the RPM, then I know what Santa is bringing me for Christmas. ;D
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Post by johnjsgems on Dec 14, 2007 11:46:35 GMT -5
I'll try to find the rpm for you. The can in the picture is for the water. The club workshop where we used to live used some old restaurant salt shakers to sprinkle grit as needed. Ive seen jars with holes punched in the lid as well. At the workshop up to three people would sit around the flat lap at a time and gossip while they worked their rocks.
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Post by johnjsgems on Dec 14, 2007 12:36:37 GMT -5
I asked Diamond Pacific's technical support guy about the rpms. He said the grit models run 265 rpm for the 12" and 100 rpm for the 18". The diamond disc unit runs 735. That's too fast for grit, it wouldn't stay on the lap plate. Hope this is helpfull.
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Saskrock
fully equipped rock polisher
Member since October 2007
Posts: 1,852
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Post by Saskrock on Dec 14, 2007 16:50:09 GMT -5
Thanks John, mine will have to be about 8" so my present 600 rpm is probably a bit quick so I will have to get another pulley, or maybe build another one. The first only cost about $40 and its nice to not have to change parts to do different things. Thanks for the help.
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