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 Post subject: What do you think of this two step faceting sequence
PostPosted: Sun Apr 16, 2017 7:10 am 
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I have been discussing faceting techniques with my friend who apprenticed and faceted for 8 years at a faceting shop in Switzerland that does stones for high end watches and now does cutting for a gem laboratory in Bangkok.

She says she cuts her initial facets on a 1000 grit lap and then jumps to a scored copper lap with SuperSyndia SSX 1.25-2.25 diamond powder and cuts her second row and polishes in one step.

She only uses 2 laps and leaves her final polish around 1 micron with super syndia.

I haven't tried it yet but I just bought a copper lap so i want to see what it looks like. I know that usually people here are polishing with 60k or 100k which is like a quarter of a micron.

What do you think?

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 Post subject: Re: What do you think of this two step faceting sequence
PostPosted: Sun Apr 16, 2017 8:27 am 
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Sounds like fairly typically commercial finishing. I've read numerous time on this site (and elsewhere), that a typical commercial polish goes to 14k, which is 1micron particle size.

It's more than adequate for most situations, and most consumers certainly couldn't tell it from a 60+k finish, nor could most jewelers I guess.

I suspect though, that it would not fit what most faceters (here) would call 'precision cut'.


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 Post subject: Re: What do you think of this two step faceting sequence
PostPosted: Sun Apr 16, 2017 10:58 am 
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I'm wondering how different does it make the finished stone? Is the 100,000 gonna bring more color out of the stone because there is more translucency in the finish and more light is passing through and coming back to your eye?

I guess this might be a reasonable approach if you are cutting really tiny stones that go around a watch face. Maybe not for the center piece of jewelry though.

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 Post subject: Re: What do you think of this two step faceting sequence
PostPosted: Sun Apr 16, 2017 3:11 pm 
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My biggest issue with it is that doing the majority of your cutting on a 1,000 grit lap would be insanely, unreasonably slow for anything over like 5mm. I personally use a 600, and even that is kinda slow for my personal tastes for anything in the 8mm range. I usually use a 260 or 325 for the initial roughing, but even then, if I start getting up to the 15-20mm range for hard materials, I'll use a platen-mounted trim saw and bring out my super-hefty 100 grit lap for mass destruction.


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 Post subject: Re: What do you think of this two step faceting sequence
PostPosted: Sun Apr 16, 2017 9:17 pm 
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I'm with Arya on the size issue. Just did a 12x16mm (synthetic) sapphire for my first sapphire attempt (what can I say: I'm stupid). I cut a boule to very roughly the right size with a trim saw, then roughed it out with a 360 before moving to 600, 3000, 50k. If I'd tried to do that with nothing but a 1000 grit it would have take me forever.... and i mean FOREVER.

Now, if cutting a small stone (watch movement stones top out at perhaps 2mm? My watch they are maybe 1mm... face stones are similarly small) then a 1000 lap is probably on the aggressive side - which is perfect for fast moving commercial cutting. Without knowing the size of stone she's cutting (and whether she's working from a preform which also changes things) I would say it's hard to gauge wether 1000 is aggressively fast or crazy slow..

I think on the final polish size is also going to be a big player, a small round stone (there's the watch movement again) nobody (except with a 10-20x loupe) is going to notice a visible difference between a 14k and a 50k polish. Watch movement stones are also not cut for optical performance after all; face stones are, but are tiny. On a big jewelry central 'bling' stone with a highly visible table, there may be very slight visible difference between a 14k and 50k polish. I don't think (see below for full disclosure) that a 200k polish is anything but a competition polish.

Commercially, time is a critical factor that isn't the case with a hobby facetor (like me). That said - I use 3 laps: 360, 600, Dominatrix (3k, 50k/oxide). There's far more time cost in switching a lap that in using a dual band lap like a dominatrix - so I can get a 50k finish with barely any extra time. The time cost is, in my opinion, in switching laps; not necessarily in switching grit sizes.

[Seriously: I've just cut my 12th stone - take everything with a pinch of salt, and presume it's just some dude who has an opinion about everything.]


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 Post subject: Re: What do you think of this two step faceting sequence
PostPosted: Sun Apr 16, 2017 9:47 pm 
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I will address several posts in this thread without directly quoting the posters:
1000 grit in what form? Sintered and if so, what is the concentration? Plated? Charged, and if so, on what type of lap?
1000 US mesh in a sintered lap can cut slowly or quickly depending on the diamond concentration.
60K US mesh is typically in the 0-1 micron range. 100K US mesh is typically in the 0-1/2 micron range.
Sounds like your friend is pre-polishing and polishing with a mesh size around 13,000 and that is a valid technique for commercial cutting.

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 Post subject: Re: What do you think of this two step faceting sequence
PostPosted: Tue Apr 18, 2017 7:02 pm 
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Polishing with 14K from a 600 finish is pretty standard commercial cutting procedure. A lot of sapphire cutters will use 8K as a final polish instead and it looks fine. Not good, but fine.

The 14K finish is streaky unless you clean the lap off and only use the embedded diamond to polish which is very slow compared to having loose diamond on the lap. The streaks can actually improve the appearance of color in a pale stone, but they make the sparkle muted in comparison to a mirror finish.


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 Post subject: Re: What do you think of this two step faceting sequence
PostPosted: Sun Apr 23, 2017 1:54 am 
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Grit, mesh, range and micron can all be a bit confusing. I have emailed Gearloose with a question about the size he is using in the battstiks.
I should imagine that she is working from a preform so the speed issue would be no problem. Watch sized stones are usually about 1mm in diameter. On that point I'm surprised that she is finishing with. On the syndia website they say that 1.25-2.25 equates to 1.68 micron median (about 1200 US grit). This seems to be a very rough finish on the stones that go into watches costing 10's of thousands, plus the stones are sold for around 1000$/ct.
Maybe 100000 is really overkill!


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