sticksinstones
starting to spend too much on rocks
Member since February 2012
Posts: 117
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Post by sticksinstones on Apr 10, 2012 23:55:45 GMT -5
Regarding the polish pads. I went with that vendor once and it was a long time ago, but I only tried them once and kept searching. I wasn't impressed with what I could get that pad to do. I can't promise anything, but I might have a 20" piece of wool carpet somewhere. I'll look around and see. My hand polisher is about that size though and I usually cut the smaller pieces left over from my 48" circles to fit it. You know what would be nearly ideal would be to recycle the center out of my 48" lap pad when I change it out - it always wears out in the outer part but the center is virtually unused and is loaded with cerium oxide by then! Might be worth considering...
Regarding your corkscrew scratches... it's not from CA or rock (neither is hard enough to do that). It's silicon carbide contamination. It's coming off (or out) of a spot that was missed in cleaning or finding it's way to the lap from some other source. It's the battle you cannot be too paranoid about when using vibrating laps. I would absolutely be removing the weights and cleaning everything ultra-thoroughly (preferably with a pressure washer) before re-starting. That tape and the gap between them is just begging to hide grit that will be vibrated out eventually in a later stage. Then that sharp, hard little bugger hits the pan and vibrates across the face of your rock making that lovely little fingerprint. And as you've seen - it only takes one grain. I guarantee that if you spend the $90 or so on that cheap electric pressure washer you'll be offering that as your own best piece of advice on these boards in a year! Just don't ever let it freeze with water in it - it won't take it...
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Post by sheltie on Apr 11, 2012 8:35:41 GMT -5
I've found that using a hose outside with adjusting heads is more than adequate for cleaning off the lap, weights, slabs, polish pad (later in the process), etc, completely. I'm sure that a pressure washer is good but unless you have other uses for it (washing the car, etc), it isn't necessary to spend that kind of money.
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sticksinstones
starting to spend too much on rocks
Member since February 2012
Posts: 117
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Post by sticksinstones on Apr 11, 2012 12:00:08 GMT -5
I've found that using a hose outside with adjusting heads is more than adequate for cleaning off the lap, weights, slabs, polish pad (later in the process), etc, completely. I'm sure that a pressure washer is good but unless you have other uses for it (washing the car, etc), it isn't necessary to spend that kind of money. I didn't start out with the pressure washer - my conviction that it was an invaluable tool in lapping came only after using both of these techniques (and a few others). There are a lot of cavities in many rocks that simply cannot be thoroughly cleaned with household water pressure, crystal lined cavities being one of the easiest places to spot the difference, if you look for it. It might seem trite to say it, but if you aren't getting the results you'd expect from your vibrating lap, it's probably rooted in something that you are sure doesn't make any difference... Something my salmon fishing guide friend keeps reminding me to explain the difference in our catch rates :blush:
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Post by sheltie on Apr 11, 2012 18:14:20 GMT -5
Trust me, if I thought that getting a pressure washer would make my slabs shine, I'd take them through the car wash! ;D
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sticksinstones
starting to spend too much on rocks
Member since February 2012
Posts: 117
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Post by sticksinstones on Apr 11, 2012 22:16:01 GMT -5
Perhaps when you are able to get them to shine you'll come back and share what you've learned. Lots of folks on the learning curve to vibrolaps will benefit. Most of them anyway :-)
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WarrenA
fully equipped rock polisher
Member since November 2003
Posts: 1,530
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Post by WarrenA on Apr 11, 2012 22:54:00 GMT -5
I am sure that I will be in big trouble for suggesting this but here goes. clean the slabs as well as you can and then put them in the dishwasher and run them, instead of the pressure washer.
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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 12, 2012 15:30:55 GMT -5
"...and then put them in the dishwasher and run them..."
LOL - Warren, I might get away with something like that if I was single but I'm sure my wife's answer would be the same as when I asked if I could put some dino bone in her pressure cooker to seal them with glue. Still a small scar visible in the right light.... :-)
SIS - I PM'ed you about the wool carpet. As to the pressure washer, I'll check it out. Actually, I'd thought of getting a WaterPik tooth cleaning thingie but maybe not enough pressure. I don't think the squiggly corkscrew scratches are coming from grit. They look like they are being made by something larger than even 120 grains and can be a bit deep. I have, occasionally, found bits of t-egg rind in the pan that were like 1/16" or a little bigger. I try to cover them completely with tape but do let a few slide when I'm running low and they are shaped the right way for rubber bands to stay put on them. Sometimes the squiggles look like they have a metallic tinge to them and I've wondered if it could be some impurity in the aluminum of the pan itself. I've drilled a 1.5" spaced grid of maybe 3/32" deep, 1/4" dimples in the pad like a Reciprolap pan but the scratches preceded my doing that. The pan had a rough, swirly surface when it was brand new but that smoothed out after the first day or two of use so I don't expect there are any jagged edges sticking up around the dimples especially after a couple months. Though, as I think of it, those dimples would work really well for a bit of rock matrix to hide in and poke up just enough to make a scratch. And, as I think more, those dimples have gotten noticeably shallower after maybe 12-20 grinds and that could allow smaller flotsam to reach the surfaces of the rocks and I do seem to feel like there are more corkies as time goes by.
I cleaned the pan, cleaned the slabs/rocks/weights, excluded anything thet either wasn't a slab or had other than a smooth rind and still ended up with squigglies. I'm now starting to think that there could be stuff that gets under the bicycle inner tube I use as a splash guard or maybe it could be coming from the lid I use, which is a water heater pan cut across the top like a 3 piece pie. I washed the inside but it's possible that some contaminant could have gotten onto the outside and then vibrated into the pan thru one of the slits. It folds into itself like a sphincter valve but I don't tape the edges so that I can access the pan and also set it like a teepee if there is a rock in the pan that's tall enough to rub against the inside. There is usually a pretty good mess of grit, polish, and God knows what else in the base that the pans sit in so not surprising if something might rattle out of it and somehow work its way up and onto the top of the lid. I'll just keep on narrowing it down until I find the culprit(s), I reckon. C-ya, Rick
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muskylounge
off to a rocking start
Member since March 2022
Posts: 3
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Post by muskylounge on Mar 1, 2022 18:19:56 GMT -5
I have been encountering a problem at the final cerium oxide polishing step while polishing slabs and blocks of cut rock. I go through all the steps that everyone uses: Initial grind with 60/90 grit, secondary grind with 220 grit, prepolish with 600 grit and finally a polish run (6 hours minimum) with cerium oxide. What I have been experiencing is that I get the desired wet look glass smooth finish around the edges but there is a hazy spot in the center. I think this is related to not getting the slab 100% flat during the initial 60/90 grind but I am not sure this is the problem. There are other possible factors. My V-lap (16" Covington) pan that I use for the rough grind (without a pad) is a bit worn, some of the cross hatches are worn down quite a bit. For the final CO polish run I use a different newer pan and that one has a thick wool pad that is saturated with optical grade CO. I am wondering if the wool pad might be the problem or if I need to redo the rough grind at 60/90 for a longer period of time to ensure better flatness and then redo all the other steps. Any thoughts
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herb
spending too much on rocks
Member since November 2011
Posts: 470
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Post by herb on Mar 2, 2022 10:20:49 GMT -5
I have been encountering a problem at the final cerium oxide polishing step while polishing slabs and blocks of cut rock. I go through all the steps that everyone uses: Initial grind with 60/90 grit, secondary grind with 220 grit, prepolish with 600 grit and finally a polish run (6 hours minimum) with cerium oxide. What I have been experiencing is that I get the desired wet look glass smooth finish around the edges but there is a hazy spot in the center. I think this is related to not getting the slab 100% flat during the initial 60/90 grind but I am not sure this is the problem. There are other possible factors. My V-lap (16" Covington) pan that I use for the rough grind (without a pad) is a bit worn, some of the cross hatches are worn down quite a bit. For the final CO polish run I use a different newer pan and that one has a thick wool pad that is saturated with optical grade CO. I am wondering if the wool pad might be the problem or if I need to redo the rough grind at 60/90 for a longer period of time to ensure better flatness and then redo all the other steps. Any thoughts It could be that your grinding pan is too dished or it could be you are not polishing long enough. I've only flat lapped thundereggs, but I always have to polish them for 14 to 20 hours before I get a real mirror polish. The edges of your pieces may look more polished than the center because there is more friction when moving over the polishing pad and the piece tends to rock ever so slightly before it overcomes the friction and moves. Think of pushing something from behind. The leading edge will dig in ever so slightly before overcoming the friction. Heres a way to check if your grinding pan is the issue: when you think you are done with a stage rinse the grit off the faces and then use a pencil to put a bunch of lines all over the face of the rock (I usually do a cross hatch pattern) then put the pieces back in the pan and run for an additional 2 or 3 minutes. When you wash the faces off again the pencil marks should all be gone or at least all equally faded across the face of the piece. If you see pencil in some areas and not in others, your piece is not flat. If the pencil is only in the center, particularly with the larger pieces then that might be from the pan being dished. Put a straight edge across a clean pan to see how much lower the center is. You can find a small machine shop to resurface the pan if needed. The big shops will charge too much because they want to do larger jobs.
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