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Author Topic: Emerald Cuts, any tips?  (Read 2188 times)

ianRobinson

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Emerald Cuts, any tips?
« on: December 18, 2018, 06:40:37 AM »
Am I the only person who finds emeralds cut tricky. On paper they look easy.

 I have just cut the pavilion of a 'Gram Easy Emerald by Jeff Graham'. 'Easy' it wasn't -  I appreciate that long parallel lines are unforgiving but it was a bugger of a job to get the facets aligned. I am tempted to simplify the pavillions down to one or two tiers.

Do you folks have to use the cheater a lot or is it just me?

ian

Rusted

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Re: Emerald Cuts, any tips?
« Reply #1 on: December 18, 2018, 07:39:03 AM »
Try not to use the cheater at all, once you start you are in a death spiral.

If your machine is not out of alignment and your laps are flat the facets should all align.

The cheapish topper laps can warp slightly due to the different expansion rates of the base stainless and the nickel plated layer, I find it best to use solid copper laps for the 3000 14000 steps before polishing, they are (should be) flat the same as the polish lap.

Talking about out of alignment. My club recently bought a used gemmasta. The person that sold it always complained about doing Emeralds, when we got it I had a look, the difference when sweeping a stone across the lap was 120 thousandths of an inch, about a tenth of an inch, there's no way you could cut a stone on that.

MakkyBrown

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Re: Emerald Cuts, any tips?
« Reply #2 on: December 18, 2018, 12:03:31 PM »
Try not to use the cheater at all, once you start you are in a death spiral.

If your machine is not out of alignment and your laps are flat the facets should all align.

The cheapish topper laps can warp slightly due to the different expansion rates of the base stainless and the nickel plated layer, I find it best to use solid copper laps for the 3000 14000 steps before polishing, they are (should be) flat the same as the polish lap.

Talking about out of alignment. My club recently bought a used gemmasta. The person that sold it always complained about doing Emeralds, when we got it I had a look, the difference when sweeping a stone across the lap was 120 thousandths of an inch, about a tenth of an inch, there's no way you could cut a stone on that.
You re-aligned by undoing the do not undo screw? Found a small plastic faced hammer works to gently tap once the screw is loosened a bit.
« Last Edit: December 18, 2018, 12:06:15 PM by MakkyBrown »

Rusted

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Re: Emerald Cuts, any tips?
« Reply #3 on: December 18, 2018, 12:47:45 PM »
Yep that's the one Makky.


ianRobinson

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Re: Emerald Cuts, any tips?
« Reply #4 on: December 30, 2018, 01:25:51 AM »
Thanks for the tips

- you could be onto something as I found the quill was out of alignment. Fortunately it is fairly easy to adjust (late series Polyhedron similar to Polymetric Scintillator).

Cheers

ian

journeyman

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Re: Emerald Cuts, any tips?
« Reply #5 on: February 16, 2019, 05:55:01 PM »
Try using just the inner section of the lap i.e. don't sweep across the whole lap, it will be dished in the middle causing the ends on the facets to droop and not be parallel.

Buch Metter

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Re: Emerald Cuts, any tips?
« Reply #6 on: March 08, 2019, 05:43:10 PM »
Don't overtighten the lap onto the platen, dishing is caused by pressure in the centre of the lap. 

Navneetgems

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Re: Emerald Cuts, any tips?
« Reply #7 on: May 26, 2020, 08:40:52 PM »
They are very tricky to do so because of the softness of the stone. They say if you can polish emeralds, you can polish any gemstone.

These are the following steps which helps in Emerald Cuts:

Step 1: Preforming
Step 2: Re-Preforming
Step 3: Faceting
Step 4: Polishing


If you have rough material in emerald lying around and during this covid-19 you are thinking to get it cut and polished, you need to watch this video https://www.youtube.com/watch?v=0ZHQXx79-9I&feature=youtu.be

Bucket

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Re: Emerald Cuts, any tips?
« Reply #8 on: May 27, 2020, 05:43:41 PM »
Pretty sure Ian was talking about the cut itself, maybe not cutting emeralds, but thanks for your input.
Common sense isn't exactly common

Faceting Frank

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Re: Emerald Cuts, any tips?
« Reply #9 on: May 27, 2020, 07:08:00 PM »
Good so see Ian got his machine sorted.
The emerald cut is a testing cut as far as machine alignment is concerned.
If the quill is hanging down at say 89.5deg to the lap you can’t really tell, but what happens as you cut each layer of an emerald cut they drift one way. So you have to use the cheater to keep them aligned and that applies to each layer. This is because the quill is gradually tipping more and more as the angle increases.
There should be some means of adjusting the quill pivot bearings, so you can tip the quill slightly. Then it’s a matter of cutting a few test emerald cuts, till they only need very minor cheater adjustments.

Dihusky

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Re: Emerald Cuts, any tips?
« Reply #10 on: May 28, 2020, 09:02:13 PM »
Another tip FF is to cut at 3 o'clock on the lap so the mast, stone and lap screw are all in line, easy to cheat the creep from spindle that's out of alignment and everything should stay the same.

When ever I do a step cut, on the first pre-polish I check the touch at 12 and 6 o'clock then tweak the bearing spindle alignment to even up the touch, best done with an accurate 8" lap if you have one and/or the machine will take an 8".

Faceting Frank

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Re: Emerald Cuts, any tips?
« Reply #11 on: May 29, 2020, 07:58:45 AM »
Something else you can do if you have a dial gauge on your machine and the mast base can spin round anyway.
Mark the edge of the lap and put a stone on the 3 o clock and 9 o clock positions, turning the lap so your always on the mark. The reason why your turning the lap is so you’re not including any lap wobble to your measurements.
Turn the base slightly and measure again. When you have found the point where the measurements are the closest, mark the mast base and always keep it pointing that way.

Navneetgems

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Re: Emerald Cuts, any tips?
« Reply #12 on: July 20, 2020, 10:20:02 PM »
If you have rough material in emerald lying around and during this covid-19 you are thinking to get it cut and polished, you need to watch this video. It will show how to preform, cut and polish emeralds – they are very tricky to do so because of the softness of the stone. They say if you can polish emeralds, you can polish any gemstone.

Step 1: Preforming
Step 2: Re-Preforming
Step 3: Faceting
Step 4: Polishing

Also,check out https://www.youtube.com/watch?v=0ZHQXx79-9I&t=202s

 

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