Joined: Tue Apr 05, 2016 7:58 pm Posts: 1424 Location: San Marcos, CA
j.mcgee_1985 wrote:
What is a good speed to cut on? Polish on? I've been hovering around 700 rpm for cutting and 1100 rpm for polish with the dyna disc laps.
Personally I use a Tin+ or Batt with 3k powder (paste is fine too) and wd40 from a 600 surface. As far as speed goes sometimes slow enough that you can feel a slight tug, then just slightly faster. But really depends on what your working with.
Awesome thanks Steve, that's exactly what I need. The light I have is bright but won't sit over the top of the stone. I like your setup, I'm going to try and copy that. I keep having problems with polish right now. Going from 600 to 1600 I'm getting all manner of results. Perfect high polish on one facet, complete doodoo on the next. Scaling, pitting, scratches.. I don't understand. Maybe it's mislabeled rather than 1600 maybe 16k? So far I'm just going from 600 to 1600 back and forth trying to figure this out. Maybe I'll go 600 to 3k next to see if it polishes different.
Do I remember correctly that you are cutting a Tourmaline?
If so, be aware that many Tourmalines (especially low clarity stones) have parallel liquid filled micro tubes as inclusions. As you polish parallel to these tubes they open up on the surface. The will look exactly like scratches.
When you hit these tubes at an obtuse angle they will look like pits.
If this is the case you will drive yourself nuts trying to polish them out. You can't do it.
Take a look at your stone under the microscope with darkfield illumination and see if this is what is happening.
Awesome thanks Steve, that's exactly what I need. The light I have is bright but won't sit over the top of the stone. I like your setup, I'm going to try and copy that. I keep having problems with polish right now. Going from 600 to 1600 I'm getting all manner of results. Perfect high polish on one facet, complete doodoo on the next. Scaling, pitting, scratches.. I don't understand. Maybe it's mislabeled rather than 1600 maybe 16k? So far I'm just going from 600 to 1600 back and forth trying to figure this out. Maybe I'll go 600 to 3k next to see if it polishes different.
Do I remember correctly that you are cutting a Tourmaline?
If so, be aware that many Tourmalines (especially low clarity stones) have parallel liquid filled micro tubes as inclusions. As you polish parallel to these tubes they open up on the surface. The will look exactly like scratches.
When you hit these tubes at an obtuse angle they will look like pits.
If this is the case you will drive yourself nuts trying to polish them out. You can't do it.
Take a look at your stone under the microscope with darkfield illumination and see if this is what is happening.
Yes I think that's exactly what's going on. It doesn't make sense any other way. I get a perfect polish on one facet and the next one gets worse then better then worse and I'm not doing anything different. Thanks Steve! Seems like it's perpendicular to the surface looking like pits but I don't have a good microscope to check, just a pocket microscope. I see some slight haze in the stone behind it so it probably goes deeper. I'll just try and minimize the pitting and leave it.
This is exactly the sort of reason that I built my Gem Cutter's Light Box to address. I designed it in order to see such things before I spent a lot of time trying to cut a polish a stone.
Ugh I got locked out of my account somehow and then just got busy with school and cutting. I gave up on that stone. I cut the big one but it turned out so small here are some pics. It took FOREVER and was non-stop problems. I definitely should have cut it in half... Wound up 9.5 cts, pretty dark still also. I got some awesome pics though.
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@j.mcgee_1985 Nice. I actually got a fresh lot of Tourmalines from Afghanistan, nice, clean ones. Just got one made, a 6 carat greenish-blue tourmaline (both pictures attached). But not entirely happy with the finishing work (maybe you guys would disagree). So I'll get other one's faceted from another person.
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Joined: Tue Apr 05, 2016 7:58 pm Posts: 1424 Location: San Marcos, CA
@j.mcgee you should be proud you were able to complete a cut that long and thin.
@mohmand: I would not disagree at all, the cutting looks okay but the final polish needs some help. Would not take much to re-dop and finish it. Your lot looks like some nice material, beautiful colors, and appear to be mostly open axis.
Awesome lot Mohmand!! I am cutting a very similar lot now as well! This is almost done, a nice apple green in incandescent but blue in white light. Like maybe 4 cts once I'm done. Might try a 14k ll dlite Mohmand, I get a perfect polish and it cuts really well (look at the side of the stone I'm cutting, I accidentally cut the end off last night on 14k, going by feel because my eyes were getting blurry...) if need be. Then 50 or 100 or leave it, I think 14 looks good, it's what the green one is on now. That color is awesome! Thanks Greg! I am happy it's done but not happy with the size or how dark it is. It took so long to get all the pitting and scratches out but I think I learned quite a bit just from trying it. I can't remember if I posted but it came out at 33.76 mm long 6.15 mm wide and 4.66 mm deep.
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Thanks! No lol, this is from my lot, his looks more saturated than this, the whole lot does really. After the nightmarish long one I was kinda disappointed so I went with an easier one. I like the blue/green mix on this one, hopefully the others have a similar color.
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