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 Post subject: Re: How do you find the center of rough to attach the dop?
PostPosted: Fri Feb 07, 2014 9:22 pm 
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Gerald,

Your method is exactly the horizontal counterpart of what I do vertically. Or vice versa, depending whether you take the plane of the table or the axis of the dop as reference. In yours the table of the stone moves vertically, in mine horizontally.

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Hans Durstling
Moncton

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 Post subject: Re: How do you find the center of rough to attach the dop?
PostPosted: Sat Feb 08, 2014 3:16 am 
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Ah....thats a themis :shock: .

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 Post subject: Re: How do you find the center of rough to attach the dop?
PostPosted: Sat Feb 08, 2014 10:19 am 
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I center my stones using sticky blue "Radico" as shown here, (second tip on this page): viewtopic.php?f=8&t=12277&p=127021&hilit=centering#p127021


The same but with blutack.

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 Post subject: Re: How do you find the center of rough to attach the dop?
PostPosted: Tue Feb 18, 2014 8:39 pm 
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does anyone have a link or web site of the Thermis vendor? Did a google search but could not find the web site.


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 Post subject: Re: How do you find the center of rough to attach the dop?
PostPosted: Tue Nov 13, 2018 11:12 am 
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I know this is an old thread but I had had to give a shout out to Hans Durstling for his idea of a centering device.

I had a transfer go all wonkyfied on me (rushed it and the epoxy wasn't cured) and was having trouble getting the stone centered, I considered getting a target dop but ran across this thread and now I'll make one.

Thanks again for sharing your wonderful idea Hans.

Jim


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 Post subject: Re: How do you find the center of rough to attach the dop?
PostPosted: Wed Nov 14, 2018 3:11 am 
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I do hand preforming first and then once my stone is clean and roughly the shape I want to be its very easy to see where the center is and then you can either dop to the table or the pavilion, whichever you prefer.

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 Post subject: Re: How do you find the center of rough to attach the dop?
PostPosted: Wed Nov 14, 2018 3:19 am 
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Justin,

It is nice to see that being trained by professional gem cutters rather than facetors is paying off for you. As you have learned, most of the money is made when pre-forming not when laying the facets on. Once pre-formed it is easy to properly position the stone on the dop. It is also the best way to deal with the subtleties of shape, inclusions, zoning, and dichroism.

As you said you can then cut either the crown or pavilion first depending on what is best for that stone.

Steve


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 Post subject: Re: How do you find the center of rough to attach the dop?
PostPosted: Wed Nov 14, 2018 10:17 am 
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Maybe Steve or Justin can help with this one, I don't need a centering device for rough I need it to center a stone that I have already cut the pavillion but screwed up rushing the transfer.

I'd prefer not to have the loss from recutting the pavillion so I was hoping to get the stone centered well enough that I could cut the crown and be done.

How would gemcutters center a stone with the pavillion already cut?

I tried by eye and it didn't happen, too far off

Will the centering device get me close enough or is there another method you would use

Is it doable or will I have to recut?

Thanks, Jim


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 Post subject: Re: How do you find the center of rough to attach the dop?
PostPosted: Wed Nov 14, 2018 3:09 pm 
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1bwana1 wrote:
Justin,

It is nice to see that being trained by professional gem cutters rather than facetors is paying off for you. As you have learned, most of the money is made when pre-forming not when laying the facets on. Once pre-formed it is easy to properly position the stone on the dop. It is also the best way to deal with the subtleties of shape, inclusions, zoning, and dichroism.

As you said you can then cut either the crown or pavilion first depending on what is best for that stone.

Steve


Maybe I'm missing something here, but what is the difference between a gem cutter and a facetor? Is it that a gem cutter may also cut cabs? Or a facetor may facet marbles rather than gemstones?

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 Post subject: Re: How do you find the center of rough to attach the dop?
PostPosted: Wed Nov 14, 2018 8:55 pm 
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The difference is just my view, but here it goes.

A facetor is someone who cuts to patterns, and likes to cut different patterns to see how they look. A facetor tries to fit the rough to a pattern he is interested in cutting.

A gem cutter tries to maximize the value of a natural piece of gem rough. He chooses a facet design that fits the stone, not the other way around. This doesn't mean that a gemcutter uses native style cutting with poor proportions, windows and sloppy meets. That is standards based, not style based. I know many "precision" and designer style cutters who I would consider gem cutters. I also know many who cut just the basic styles which are standard mixed cuts in various shapes.


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 Post subject: Re: How do you find the center of rough to attach the dop?
PostPosted: Wed Nov 14, 2018 11:41 pm 
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JCD wrote:
Maybe Steve or Justin can help with this one, I don't need a centering device for rough I need it to center a stone that I have already cut the pavillion but screwed up rushing the transfer.

I'd prefer not to have the loss from recutting the pavillion so I was hoping to get the stone centered well enough that I could cut the crown and be done.

How would gemcutters center a stone with the pavillion already cut?

I tried by eye and it didn't happen, too far off

Will the centering device get me close enough or is there another method you would use

Is it doable or will I have to recut?

Thanks, Jim


Jim,

It should be able to be done. I will be happy to see if I can help you with this.

What shape is the stone?

What cutting machine?

What transfer jig?

Do you have a flat table already roughed onto the stone?

If so, did you mount the stone with this flat against a dop when you cut the pavilion?

Steve


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 Post subject: Re: How do you find the center of rough to attach the dop?
PostPosted: Thu Nov 15, 2018 7:17 am 
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Thanks Steve,

Stone shape is rectangular

Ultra Tec V2

Not sure about the jig I got it with the machine I'm assuming an old
Ultra tec jig

Yes flat table roughed in

Yes flat against the dop when I cut the pavillion

When I tried to eyeball it, I had the flat against a large dop to keep the same orientation but I got off side to side and a slight twist that's where I thought a centering device would be what I needed.

EDIT: Ok it's starting to come in, I'm making serious adjustments to height and having to make some index adjustments as well, not easy but I might get it.

Jim


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 Post subject: Re: How do you find the center of rough to attach the dop?
PostPosted: Thu Nov 15, 2018 9:21 am 
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1bwana1 wrote:
The difference is just my view, but here it goes.

A facetor is someone who cuts to patterns, and likes to cut different patterns to see how they look. A facetor tries to fit the rough to a pattern he is interested in cutting.

A gem cutter tries to maximize the value of a natural piece of gem rough. He chooses a facet design that fits the stone, not the other way around. This doesn't mean that a gemcutter uses native style cutting with poor proportions, windows and sloppy meets. That is standards based, not style based. I know many "precision" and designer style cutters who I would consider gem cutters. I also know many who cut just the basic styles which are standard mixed cuts in various shapes.


I would think that anyone who cuts, always chooses a facet design that suites the shape of the rough. The only time I would think it would be the other way around would be to do a proof cut on a new design, and then you are usually cutting a very inexpensive piece of rough or man made material so recovery is not a concern.

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 Post subject: Re: How do you find the center of rough to attach the dop?
PostPosted: Thu Nov 15, 2018 11:17 am 
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JCD wrote:
Thanks Steve,

Stone shape is rectangular

Ultra Tec V2

Not sure about the jig I got it with the machine I'm assuming an old
Ultra tec jig

Yes flat table roughed in

Yes flat against the dop when I cut the pavillion

When I tried to eyeball it, I had the flat against a large dop to keep the same orientation but I got off side to side and a slight twist that's where I thought a centering device would be what I needed.

EDIT: Ok it's starting to come in, I'm making serious adjustments to height and having to make some index adjustments as well, not easy but I might get it.

Jim


What pattern are you cutting?

Keyed or non keyed dop?


Last edited by 1bwana1 on Thu Nov 15, 2018 11:49 am, edited 1 time in total.

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 Post subject: Re: How do you find the center of rough to attach the dop?
PostPosted: Thu Nov 15, 2018 11:46 am 
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Precision Gem wrote:
1bwana1 wrote:
The difference is just my view, but here it goes.

A facetor is someone who cuts to patterns, and likes to cut different patterns to see how they look. A facetor tries to fit the rough to a pattern he is interested in cutting.

A gem cutter tries to maximize the value of a natural piece of gem rough. He chooses a facet design that fits the stone, not the other way around. This doesn't mean that a gemcutter uses native style cutting with poor proportions, windows and sloppy meets. That is standards based, not style based. I know many "precision" and designer style cutters who I would consider gem cutters. I also know many who cut just the basic styles which are standard mixed cuts in various shapes.


I would think that anyone who cuts, always chooses a facet design that suites the shape of the rough. The only time I would think it would be the other way around would be to do a proof cut on a new design, and then you are usually cutting a very inexpensive piece of rough or man made material so recovery is not a concern.



I would thinks so too, but I often see otherwise. People cut to the length/width ratios, pavilion/crown percentages, table sizes, and at the indexes and angle numbers on published diagrams. Rarely does a natural piece of gem rough return maximum yield, allow you to minimize color issues, or strategically place inclusion to hide them under facet junctions when cutting from a diagram this way. A facetor follows a cookbook approach to cutting. A gem cutter, even when cutting a specific arrangement of a cut will alter these attributes as he works his way through the stone in order to maximize the result and yield.

A common process for the best natural gem cutters I see in shops around the World is :

Clean and shape the rough by hand. The rough tells you the L/W, H/W, pavilon/crown ratio, and outline. The vast majority of weight loss takes place during this stage. Then dop the stone and lay the facets on in the desired pattern following the contours that the preformer set. A gem cutter will look at a diagram and cut the pattern, to fit an individual stone without any index or angle numbers.

The preformer is the most valued (and highest paid) roll in most shops. In Idar some of the best gem dealers I know preform almost all their stones themselves, then pass the stone to a worker to lay the facets on.

Of course this workflow is for fine gems, and is altered for calibrated stones. The preformer works to get the rough shaped to meet the largest calibrated L/W, Depth ratios possible. The people then laying the facets on do have to cut to prescribed indexes and angles so that stones match.


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