polaszko
having dreams about rocks
Member since August 2020
Posts: 58
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Post by polaszko on May 14, 2022 7:29:21 GMT -5
Okay, so without further ado I will say what my problem is. I bought my first flat lap recently - it's 14,5 inch selfmade from talented rock polisher from Nowy Kościół in Poland (it's familiar to this one, but without automatic water supply: www.diamondpacific.com/wp-content/uploads/2021/06/18-rotating-disc-flat-lap-scaled.jpg). It's my first lap, so I started learning how to use it. My starter rocks are septarian nodules, yellow calcite, and small galaxy stone (small sample of material that I'll work with in future). Between grit F500 and F1200 (13 and 3 micron) I ran into a problem of scratches that started to appear on the surface of stones. My first thought was contaminated wheel or grit, but quickly I discovered that small pieces of stones broke off and scratched the hell out of my stones. And that's exactly my problem. I don't know if it's normal, whether my stones just like to crumble, or I'm pressing on them too much or too weak. I'll apriciate any advise.
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Post by hummingbirdstones on May 14, 2022 10:21:09 GMT -5
Wish I could help you out, but I just had that happen to me on the back of a stone using metal laps. I got so aggravated I ended up not finishing the back on that stone. It was a moss agate and micro druzies were getting yanked out by the metal laps. I'm guessing it's the stones. I could hear it scratch the back of the stone when it happened. Had to use a straight edge razor blade parallel to the surface of the lap to pick it out of there. After quite a few times of it happening, I gave up. I was not using much pressure on the stone at all. Now that I think about it, maybe I needed to use more pressure to stop it from happening. Calcite is soft though, so I don't think you would want more pressure.
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polaszko
having dreams about rocks
Member since August 2020
Posts: 58
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Post by polaszko on May 14, 2022 10:55:08 GMT -5
So maybe I should start learning with harder material. I have some thundereggs from Nowy Kościół, I can select ugliest, so if I screw them up it won't be a huge loss.
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Post by parfive on May 14, 2022 11:16:54 GMT -5
Can you tell if the broken chips are coming from the center or the edge of the slabs?
A slight bevel on the edge all around the perimeter can help protect a weak area.
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polaszko
having dreams about rocks
Member since August 2020
Posts: 58
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Post by polaszko on May 14, 2022 11:49:21 GMT -5
Can you tell if the broken chips are coming from the center or the edge of the slabs? A slight bevel on the edge all around the perimeter can help protect a weak area. They are coming both from the edge and from the center of the slab. Depends on the stone. Maybe this beval is a solution for some, but it will be very noticeable, won't it?
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snetbonaut
starting to spend too much on rocks
Member since February 2022
Posts: 129
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Post by snetbonaut on May 21, 2022 12:58:48 GMT -5
So maybe I should start learning with harder material. I have some thundereggs from Nowy Kościół, I can select ugliest, so if I screw them up it won't be a huge loss. I have been doing something similar. Early on I decided that I would save my "good rocks" for a time when I have developed more skills. While I am aware that this may never happen, I have embarked on a journey of learning how to put straight lines in and take them out. I have begun to recognize when I am holding piedras del diablo that will crack, crumble, or undercut. I don't know what to do with them, but I recognize them. I have polished granite, jasper, all kinds of quartzy stuff, ugly agates, and a few rocks of unknown origin. I am getting better at understanding that sometimes, that fracture is just going to have to be an "exotic imperfection" that proves to the recipient that I did it by hand. I've also been doing things like rounding off square rocks and squaring up round rocks. The best two things I have picked up so far has been pretty simple. The first few weeks I used the Lap, I cut on Turbo and ground away. More recently, I have begun to understand that a slow rotation is sometimes a better way to wear down the previous grit scratches. I am much more aware of the fact that my discs have three slightly different levels of abrasion. The "center" of the disc is rougher than the middle of the disk and the outer edge is the roughest of the three surfaces. I assume this is because the majority of my shaping/smoothing occurs in the middle of the disc. I am gonna guess that I still have a long run before I stop chipping stones and deburring fingernails.
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polaszko
having dreams about rocks
Member since August 2020
Posts: 58
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Post by polaszko on May 29, 2022 17:01:40 GMT -5
I tested that slight bevel on calcite. I have done only two specimens yet, but it's not noticeable after polish, actually it grinds away during pre polish (damn calcite is soft). Anyway I'll continue testing on my worst thundereggs and more calcite. I'll write about any results. Thanks for now.
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