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Author Topic: Emerald Cuts, any tips?  (Read 640 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. 

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