Lapping machine

I'm new to this group because it is an active group and I think I might find what I need here. That said...I make Tiffany-style
translucent stone lampshades and cut 3/16" slabs using an 18" diamond slab saw. The largest slabs I can cut are about 7 1/4" on a side. This saw leaves striations on the cut surface which need to be sanded off and further sanded to a pre-polish and then polished on a polishing drum. At present I am using a high speed dry sander manufactured by Richardsons rock ranch. As you can imagin, this is a tricky operation with 3/16" slabs. Also the pieces will get very hot if sanded too long and they can be cought by the sanding disks and discharged violently...arrrg!
Once the pieces are polished I can begin to cut out pattern pieces. My issue has been that it takes a very long time to go from the slabs to a polished piece of stone. I currently use translucent stone which veries in hardness from relatively soft to gem quality brazillian agate.
What size lap do I need to work my 7 1/4" slabs? I don't have any experience using a lapping machine, so your expertise is necessary.
Needing your advice
Sincerely,
Gary A. Betts
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Take a look at the counter top specialty. Those pros cut and polish hard stone slabs by the acre. Look up a local shop and make a visit. See what they do and how they do it. Ask for some guidance. In the mean time, use google to find a supplier of the cutting tools they use -- polishing si done with diamond faced pads -- EXPENSIVE!
(Amazon.com product link shortened)
You might even consider asking the counter top people to polish your stones on a commercial scale and find it's cheaper than doing a few shards at a time. Spend your valuable time designing and assembling the shades.
You might also take a look at their material suppliers, known as "slab yards." The slab yard will have thousands of slabs, usually 8 X 10 feet X 1.5 inches thick, and some may be attractive to you. Costs nothing to look.
Pat
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i made my own lap to do face and edge work on slabs of glass. it's 24" in diameter, but could be scaled up/down. i use silicon carbide loose grit, which is WAY cheaper than diamond pads, needs less rotation speed on the lap, and lots less water, which leads to lots less mess.
http://groups.msn.com/chaniarts/woodworking.msnw?action=ShowPhoto&PhotoIDC0
you want something at least 2x as wide as the longest dimension as what you want to grind, because the center does no grinding if your slab spans it, unless your object can fit across a chord of the circle. i routinely polish the rims of 23" diameter bowls
http://www.glassartists.org/Img38838_Glow_in_the_Dark_Spotted_Sink_.asp
so i need the full diameter of the lap.
plans available upon request.
regards, charlie http://glassartists.org/chaniarts
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You might also visit / talk to the people that manufacture tomb stones and monuments.
Wolfgang
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wascocountry wrote:

This may not be what you're looking for, but it's something that I call a lapidary grinder. My wife makes pottery and then embeds natural stone in epoxy in bands around the pot and grinds it off flush. She wanted a wet wheel and all of the commercially available ones run from expensive to extremely expensive compared to regular grinders. I made one from parts from a washing machine. It's a little crude and does have a bug or two (runs too slow) but it does work and I've only got about $80 in it (the expando wheel costs about $50 alone) compared to $500+ for the professional models. See it here:
http://powdercoatoven.4t.com/Misc%20photos/Misc%20photos.html
--
Gary Brady
Austin, TX
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You need a vibrating lap for this. The tombstone and countertop guys won't want to deal with small odd-sized pieces of stone like you have. With a vibrating lap you can load a few slabs in and leave them a while to get rid of saw marks, then change grits and go all the way to polish. They give more uniform results than a rotary lap, since you aren't working against a wheel with variable surface-feet per minute depending on whether you're on the edge or in the middle. It may be slower than the technique you're used to, but it's a lot safer, and easier on the material. Here's a link: http://www.kingsleynorth.com/skshop/search_results2.php?catID 6
Andrew Werby www.unitedartworks.com

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