mikeinsjc
spending too much on rocks
Member since June 2010
Posts: 329
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Post by mikeinsjc on Apr 27, 2012 21:07:33 GMT -5
I am getting a decent polish with stones from a 600 grit belt on a bull wheel to a vibrating flat lap with cerium, running 12 hour cycles. But I cannot, cannot, CANNOT hand polish to a decent sheen. I have a garage full of equipment, which I am thinking about lining up in the street and running over it all with my Suburban, except tires are $200 a pop. I have Poly arbors. Bull wheel. Richardson Ranch sander and polisher. It's pathetic.
So, on my poly arbor I have 3" expandable drums with 1200, 3000, and 14,000 grit diamond belts. I can get a better finish with a 600 grit belt on a bull wheel than with the 1200 or the 3000 diamond belt. So I say to myself"SURELY, the 14,000 belt will give a nice polish without decorating the entire side of my house with a thin film of cerium."
Wrong. Still scratches. So my question is this. I want a mirror finish, or at least as nice as my vibrating lap is producing, WITHOUT using cerium. Is such a shine possible to obtain with just diamond belts?
My last option would be to fly someone to California to show me how to do this.
This can't be rocket science. Do I need to join some secret polishing cult to be privy to the methods? I have exhausted my list of expletives-they don't help either.
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Post by Donnie's Rocky Treasures on Apr 28, 2012 7:26:38 GMT -5
My question would be what are you trying to get a mirror finish on?
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Post by Hard Rock Cafe on Apr 28, 2012 7:49:13 GMT -5
LOL Donnie! Try as you might, you'll never get a mirror polish on sandstone!
Okay, back to the question at hand. Donnie's point is a good one, as soft stones won't acquire a mirror finish.
If you're trying to do slabs or other flat surfaces, those are extremely hard to do on wheels smaller than a bull. I think Bobby1 has a technique for dry sanding with worn belts on an 8"x3" wheel.
If you're still seeing scratches it means you need to spend more time on early sanding stages. All of the visible scratches should be gone by the time you get to the 600 belt. That usually means more time on the 280 (assuming standard belt sequence).
Hope that helps.
Chuck
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Post by stonesthatrock on Apr 28, 2012 8:34:54 GMT -5
where in ca. are you......... ralph and i are coming over for a show in yucipia may 17 th mary ann
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mikeinsjc
spending too much on rocks
Member since June 2010
Posts: 329
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Post by mikeinsjc on Apr 28, 2012 22:20:44 GMT -5
I am polishing Montana moss agate and petrified wood.
On a bull wheel (or probably anything else) a rock polished on a well-worn 100 grit belt will be scratched by a new 220, i.e. it will look worse. Ditto for all grits. A rock sanded on a well-worn 400 will be scratched by a new 600. Rocks sanded on a 600 on its last breath will still show scratches.
And on it goes. The rock sanded on the 600 belt near the end of its life will be scratched by a 3000 diamond belt. So I am back to my original question; Can I get a vibrating-lap quality finish using only diamond belts on expando drums? If yes, what is the grit sequence of diamond I need to use?
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Post by helens on Apr 29, 2012 0:11:17 GMT -5
Maybe this is a dumb question, but are you washing the rocks really well between grits?
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Post by gingerkid on Apr 29, 2012 1:24:53 GMT -5
I think some petrified wood undercuts. With the pet wood, I discovered lovely scratches after polishing with polishing compound (cerium oxide), and just decided to go back to polishing with diamond paste and no polishing compound.
Try and see if the 14k belt may be the problem. I've noticed that I can use the 600 and 12k grit diamond belts and not see any fine scratches until I use the 14k, then have to start all over again.
Hope you find out how to get rid of those scratches. I feel your pain.
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rykk
spending too much on rocks
Member since September 2011
Posts: 428
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Post by rykk on Apr 29, 2012 1:38:59 GMT -5
Are you getting enough water on your belts? Too much isn't good but not enough will let heat build up and, also, bits of the sanded rock could be stuck on the belts and cause scratches.
If the water supply is right, how is it delivered? Sometimes rigs with "spitter" pumps and a common water pan shared by multiple wheels with different grits can have problems if there is grit/diamond from coarser belts in the water. Best to change the water every time between grits.
The worst problem I had - other than not being able to get rocks flat - when all I had was a flat spinner lap was little, tiny "micro-scratches". They weren't actually scratches, they were little fractures just under the surface of the rock/slab. Bruneau was a real bear. I *think* the term for these fractures is *crazing". It's caused by heat buildup from either the lap being too dry, too much pressure, or both. Take a close look at your rocks and see if they are really scratches. i reckon probably they are because I only saw crazing when I was polishing.
Another trick I used was to have a toothbrush at hand to, occasionally, run over the lap disk while it spun with extra water from a spray bottle to clean off the built up quartz. I know how you must feel, man - sheesh, it took me like 6 months and 3 days to get a good polish on this big Wave Hill nodule that I'd selected to my first polished rock. 6 months dorking with the lap... and then 3 days when I finally got lucky and picked up a vibe lap at ebay. :-)
I get scratches when I use expando drums, too. I tend to get in a hurry and push too hard on the rocks. Good luck, you'll get it figured out. Rick
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