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 Post subject: Re: What causes a misaligned pavilion girdle before transfer
PostPosted: Sat Oct 16, 2021 4:51 pm 
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Hi teefer, while it sounds like you've solved your problem, I think this thread would be a good place to post my experience with a similar problem (misaligned pavilion girdle).

I have a GemMaster II and consistently had misaligned girdles. I checked everything that I found in online references and suggestions by others, but nothing worked. I checked rounouts (dop end on quill, quill w/o dop, platen, platen drive) and facet head to platen sweep planarity (both mast rotational sweep and moving mast closer/further from platen). The problem was finally found when I tried using a "monster dop" and found that while mast and platen were in alignment, my facet head quill/dop were not perfectly perpendicular to the platen. After having spent hours upon hours checking alignments, it was a half-hour fix (adjustment screws on my GMII facet head)! See pages 9-10 of the linked article that I found.

Hopefully, this will save someone else the misery I put my self through due to thinking that a runout gauge and sweep tests would identify all possible problems.

http://lapidaryworld.com/pdf/faceting_machine_alignment.pdf


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 Post subject: Re: What causes a misaligned pavilion girdle before transfer
PostPosted: Sun Oct 17, 2021 4:25 pm 
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Very informative article and technics implemented. I wonder if say a 20mm diameter flat dop would be okay if your not cutting stones the sizes of a 2" dop would need calibrated for. Just speaking in the degree calibration with the plastic gauges. I personally us a digital degree meter not all that expensive for checking tha angle calibration on my Scintilator. As far as laps go they are going to differ from lap to lap, but the platen and if you always use a master under your laps then it to needs checked as well. The article doesn't address the mast perpendicularity adjustments or maybe I missed it.

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 Post subject: Re: What causes a misaligned pavilion girdle before transfer
PostPosted: Sun Jul 31, 2022 8:42 pm 
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glhays wrote:
I always found this article to be a tad controversial, but speaks to the point of a opinion and that we all have a reason for our individual technics and methods.
https://usfacetersguild.org/be-a-performer-not-a-preformer/


I think this line sums up the position of the author of that article perfectly.

" Let’s face it. Your finished stone will only be 20% to 25% of the weight of the rough you started with."

His position is that preforming results in smaller stones. His expectations of recovery disproves that statement. You could really stop reading the article at that point.

I have found that those who use meet point faceting are in fact getting 20% to 25% recoveries.

If you really are only getting those kinds yields you are wasting material, money, and profit, for no functional gain in stone performance.

He then goes on to describe what he views as his efficient cutting and polishing lap sequence. He must be kidding 6 laps!

This is just plain ridiculous. The vast majority of time I use only two laps to cut and polish a stone. The second lap is a two banded pre-polish/final polish lap so you could count it as 2 if you like.

Without exception, the best cutters I know in the World all preform. They work on an optimized progression of laps designed to minimize the number of laps used, and the number of times each facet is touched in the process.

Personally, when my recovery falls below 40% I am very disappointed. I often achieve 50% and up.

I don't achieve these results by sacrificing performance. I do not accept windows in the stones, and my end result must achieve the "Excellent" grade when graded with the G.I.A. cutting grade criteria. These are precision cut stones, and not commercial cuts.

Greg (gdHayes) and I had a mutual friend who was a World class performer. He taught Greg, and I was taught by the same Germans who taught him. So we share a common respect for this skill. Greg understands the value of good preforming, and employs it in his cutting. The truth is that to a great extent the art of gemstone cutting is the art of the preform. The majority of profit made in gemstone cutting is made at three levels. When and how you buy the rough, when and how you preform the stone, and when at at what level you sell the stone. The laying on and polishing of the facets is one of the least determinant parts.

In cutting shops that work with high end material the most senior and highest paid person is the pre-former. The facetors are the junior people. It is the pre-former that the owner depends on to help select, sort, and value rough to be purchased.

Another benefit is that a properly trained gemstone cutter using the pre-forming method can take a piece of rough of any L/W/D ration, look at a facet pattern and cut it without the aid of any diagrams. Thus maximizing recovery. I spend a great deal of time training my students to cut without diagrams. Cookbook following of diagrams is the enemy of proper gem cutting.

Understanding pre-forming is the difference between a gemstone cutter and a hobby facetor. Two very different approaches.


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 Post subject: Re: What causes a misaligned pavilion girdle before transfer
PostPosted: Tue Aug 02, 2022 1:21 pm 
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@drbob do you have an opinion on your reposts of prior posts?

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 Post subject: Re: What causes a misaligned pavilion girdle before transfer
PostPosted: Tue Aug 09, 2022 2:27 pm 
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I think recovery is more a function of the rough you start with, rather than the cutting method. If you start with a nice round Montana sapphire that is clean, you will get a very high recovery, if you start with one of those typical sapphires from Ilakaka that are flat and kind of twisted, you won't get a high recovery.

A lot of the more hobby cutters are cutting lab created material. If you want to cut a round lab stone, and you saw cut some rough, unless you have a saw blade that cuts tight curves, you will start out with a square shape. I don't care how you cut, you are not going to get 50% recovery from this rough.

The same is true if you are working with rough that has inclusions and looking to cut a clean stone. You can easily preform away 50% of the material.

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 Post subject: Re: What causes a misaligned pavilion girdle before transfer
PostPosted: Thu Aug 11, 2022 12:09 pm 
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1bwana1 wrote:
glhays wrote:
I always found this article to be a tad controversial, but speaks to the point of a opinion and that we all have a reason for our individual technics and methods.
https://usfacetersguild.org/be-a-performer-not-a-preformer/


I think this line sums up the position of the author of that article perfectly.

" Let’s face it. Your finished stone will only be 20% to 25% of the weight of the rough you started with."

His position is that preforming results in smaller stones. His expectations of recovery disproves that statement. You could really stop reading the article at that point.

I have found that those who use meet point faceting are in fact getting 20% to 25% recoveries.

If you really are only getting those kinds yields you are wasting material, money, and profit, for no functional gain in stone performance.

He then goes on to describe what he views as his efficient cutting and polishing lap sequence. He must be kidding 6 laps!

This is just plain ridiculous. The vast majority of time I use only two laps to cut and polish a stone. The second lap is a two banded pre-polish/final polish lap so you could count it as 2 if you like.

Without exception, the best cutters I know in the World all preform. They work on an optimized progression of laps designed to minimize the number of laps used, and the number of times each facet is touched in the process.

Personally, when my recovery falls below 40% I am very disappointed. I often achieve 50% and up.

I don't achieve these results by sacrificing performance. I do not accept windows in the stones, and my end result must achieve the "Excellent" grade when graded with the G.I.A. cutting grade criteria. These are precision cut stones, and not commercial cuts.

Greg (gdHayes) and I had a mutual friend who was a World class performer. He taught Greg, and I was taught by the same Germans who taught him. So we share a common respect for this skill. Greg understands the value of good preforming, and employs it in his cutting. The truth is that to a great extent the art of gemstone cutting is the art of the preform. The majority of profit made in gemstone cutting is made at three levels. When and how you buy the rough, when and how you preform the stone, and when at at what level you sell the stone. The laying on and polishing of the facets is one of the least determinant parts.

In cutting shops that work with high end material the most senior and highest paid person is the pre-former. The facetors are the junior people. It is the pre-former that the owner depends on to help select, sort, and value rough to be purchased.

Another benefit is that a properly trained gemstone cutter using the pre-forming method can take a piece of rough of any L/W/D ration, look at a facet pattern and cut it without the aid of any diagrams. Thus maximizing recovery. I spend a great deal of time training my students to cut without diagrams. Cookbook following of diagrams is the enemy of proper gem cutting.

Understanding pre-forming is the difference between a gemstone cutter and a hobby facetor. Two very different approaches.


I have to say, this is the most interesting post I have read in a very long time. So many of the faceters these days - including myself - have a hobbyist outlook because of how we learned. I taught myself by trial and error using the Vargas books, so my method is somewhere between meetpoint and what you describe here. Most of us are completely unaware of the advantages of preforming, the hobbyist mostly sees it as a time and lap saving method.

I may be the only one, but I find the subject of why to preform fascinating enough to warrant its own thread rather than clutter up this one with a tangential discussion. Perhaps this is irrelevant however, of the three points you mention where profit is made, it is only the second that is available to most of us.


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 Post subject: Re: What causes a misaligned pavilion girdle before transfer
PostPosted: Thu Aug 11, 2022 3:12 pm 
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@jdowney, start a topic, lets see where it goes. 1bwana is doing a zoom meet on the subject, here is the thread link https://www.gemologyonline.com/Forum/phpBB2/viewtopic.php?f=8&t=2501&start=150

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 Post subject: Re: What causes a misaligned pavilion girdle before transfer
PostPosted: Thu Aug 11, 2022 4:04 pm 
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Precision Gem wrote:
I think recovery is more a function of the rough you start with, rather than the cutting method. If you start with a nice round Montana sapphire that is clean, you will get a very high recovery, if you start with one of those typical sapphires from Ilakaka that are flat and kind of twisted, you won't get a high recovery.

A lot of the more hobby cutters are cutting lab created material. If you want to cut a round lab stone, and you saw cut some rough, unless you have a saw blade that cuts tight curves, you will start out with a square shape. I don't care how you cut, you are not going to get 50% recovery from this rough.

The same is true if you are working with rough that has inclusions and looking to cut a clean stone. You can easily preform away 50% of the material.


I agree the rough you start with will most likely be a factor in end yield results no matter your technics and toolsets. I do not see or feel preforming as a cutting method. More like not leaving the eggshell in the omelet.
I do not think it matters where rough originates, makes much difference. If it is clean its clean if not its not.

As far as lab created material all I can say to your points are wise choices of orientation to get the most from the boule as possible is a thought. Of course just trimming off a hunk, throw it on the dop, go to cutting that design, is a method of waste. You can trim out lab material quite easily to get the most possible yields without a bendable blade. And some blades like wider kerf sintered blades can actually be a makeshift arbor to smooth off points and edges. 50% recovery is surely possible, if wise use of the rectangular or square is cut appropriately for what it is, I agree most hobby cutters are going to take and make a rectangle a pear or oval or some other poor choice for the given rough. Many will over compensate the material needed for a design in any case. Just in-experience.

Rough with flaws, inclusions..... easily preform away 50%? Is it not already a sort of waste, when a clean stone is the desired result. Trim it off, it may have a use down the road. Kind of like a hard boiled egg, that shell is just a waste, unless you use it for a garden or something.

Preforming is a wise course of studying, evaluating, orientating gem rough for the best maximum yield that individual piece wants to be. The first thing I was taught in preforming was let the rough be what it wants to be, let it tell you the shape it should be, let it tell you if an inclusion can be hidden or praised for its own uniqueness in some way.

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 Post subject: Re: What causes a misaligned pavilion girdle before transfer
PostPosted: Thu Aug 11, 2022 7:46 pm 
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You give me cube shaped (which is a square in all directions) and I should be able to get very close to a 50% recovery in a SRB cut round. More if you don't need a standard brilliant cut.

What is called a "sawable" in Diamond rough is just such a shape, and that kind of recovery is commonly achieved on such rough shapes.


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 Post subject: Re: What causes a misaligned pavilion girdle before transfer
PostPosted: Sun Aug 14, 2022 1:24 pm 
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1bwana1 wrote:
You give me cube shaped (which is a square in all directions) and I should be able to get very close to a 50% recovery in a SRB cut round. More if you don't need a standard brilliant cut.

What is called a "sawable" in Diamond rough is just such a shape, and that kind of recovery is commonly achieved on such rough shapes.


I'll take you up on that. Email me your address, and I'll ship you cube to cut.

If you look on GemCut Studio, the program starts out with a cube with a volume of 1. Make a SRB and then check the volume and it's around 0.22 So that's 22% yield.

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 Post subject: Re: What causes a misaligned pavilion girdle before transfer
PostPosted: Sun Aug 14, 2022 1:29 pm 
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glhays wrote:
Precision Gem wrote:
I think recovery is more a function of the rough you start with, rather than the cutting method. If you start with a nice round Montana sapphire that is clean, you will get a very high recovery, if you start with one of those typical sapphires from Ilakaka that are flat and kind of twisted, you won't get a high recovery.

A lot of the more hobby cutters are cutting lab created material. If you want to cut a round lab stone, and you saw cut some rough, unless you have a saw blade that cuts tight curves, you will start out with a square shape. I don't care how you cut, you are not going to get 50% recovery from this rough.

The same is true if you are working with rough that has inclusions and looking to cut a clean stone. You can easily preform away 50% of the material.


I agree the rough you start with will most likely be a factor in end yield results no matter your technics and toolsets. I do not see or feel preforming as a cutting method. More like not leaving the eggshell in the omelet.
I do not think it matters where rough originates, makes much difference. If it is clean its clean if not its not.

As far as lab created material all I can say to your points are wise choices of orientation to get the most from the boule as possible is a thought. Of course just trimming off a hunk, throw it on the dop, go to cutting that design, is a method of waste. You can trim out lab material quite easily to get the most possible yields without a bendable blade. And some blades like wider kerf sintered blades can actually be a makeshift arbor to smooth off points and edges. 50% recovery is surely possible, if wise use of the rectangular or square is cut appropriately for what it is, I agree most hobby cutters are going to take and make a rectangle a pear or oval or some other poor choice for the given rough. Many will over compensate the material needed for a design in any case. Just in-experience.

Rough with flaws, inclusions..... easily preform away 50%? Is it not already a sort of waste, when a clean stone is the desired result. Trim it off, it may have a use down the road. Kind of like a hard boiled egg, that shell is just a waste, unless you use it for a garden or something.

Preforming is a wise course of studying, evaluating, orientating gem rough for the best maximum yield that individual piece wants to be. The first thing I was taught in preforming was let the rough be what it wants to be, let it tell you the shape it should be, let it tell you if an inclusion can be hidden or praised for its own uniqueness in some way.



If I am cutting flame fusion boules, then the material is mostly around $0.04 per ct. So I am way more concerned about time than cost of material. What does it matter if the piece I saw cost $0.40 or $0.80 ?

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 Post subject: Re: What causes a misaligned pavilion girdle before transfer
PostPosted: Sun Aug 14, 2022 2:28 pm 
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Precision Gem wrote:
If I am cutting flame fusion boules, then the material is mostly around $0.04 per ct. So I am way more concerned about time than cost of material. What does it matter if the piece I saw cost $0.40 or $0.80 ?

If your cutting whatever boules, time is moot. What does it matter the cost of the piece you have sawn? Did the FF material jump from $.04 to $.40 - $.80 in cost prior to your sawing? Or is that typo?

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PostPosted: Sun Aug 14, 2022 2:58 pm 
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glhays wrote:
Precision Gem wrote:
If I am cutting flame fusion boules, then the material is mostly around $0.04 per ct. So I am way more concerned about time than cost of material. What does it matter if the piece I saw cost $0.40 or $0.80 ?

If your cutting whatever boules, time is moot. What does it matter the cost of the piece you have sawn? Did the FF material jump from $.04 to $.40 - $.80 in cost prior to your sawing? Or is that typo?


No, the material is $0.04 per ct. So if I cut a 10 ct piece or a 20 ct piece to cut the same size finished stone, what's the difference? 40 cents or 80 cents. My time is at least $1 per minute, so I am not going to spend time to fret over 40 cents of material. Maybe for you it is, not for me.

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 Post subject: Re: What causes a misaligned pavilion girdle before transfer
PostPosted: Sun Aug 14, 2022 3:17 pm 
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Precision Gem wrote:
1bwana1 wrote:
You give me cube shaped (which is a square in all directions) and I should be able to get very close to a 50% recovery in a SRB cut round. More if you don't need a standard brilliant cut.

What is called a "sawable" in Diamond rough is just such a shape, and that kind of recovery is commonly achieved on such rough shapes.


I'll take you up on that. Email me your address, and I'll ship you cube to cut.

If you look on GemCut Studio, the program starts out with a cube with a volume of 1. Make a SRB and then check the volume and it's around 0.22 So that's 22% yield.


Try this:

Don't place the table on one of the existing flat surfaces of the cube as you probably did in Gem Cut Studio. Instead turn it like a top so that a tip is directly up, and a tip is directly down. Now saw it above the center line at at point that will give you the desired table percentage size. You will end up with a square preform but with the Crown angles, and pavilion angles already in. Now all you have to do is round out the shape, and lay the facets on. You will end up with two stones, saving about 50% of the original cube weight.

The picture of the process below is for a Diamond sawable, which is actually a most often a dodecahedral, but also commonly a cube. In a colored stone you can just accept the 45 degree angles of the rough rather than the exact angles that diamonds require.


Attachments:
DiamondSawing.jpg
DiamondSawing.jpg [ 83.97 KiB | Viewed 1150 times ]


Last edited by 1bwana1 on Sun Aug 14, 2022 3:50 pm, edited 1 time in total.
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 Post subject: Re: What causes a misaligned pavilion girdle before transfer
PostPosted: Sun Aug 14, 2022 3:49 pm 
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Precision Gem wrote:
glhays wrote:
Precision Gem wrote:
If I am cutting flame fusion boules, then the material is mostly around $0.04 per ct. So I am way more concerned about time than cost of material. What does it matter if the piece I saw cost $0.40 or $0.80 ?

If your cutting whatever boules, time is moot. What does it matter the cost of the piece you have sawn? Did the FF material jump from $.04 to $.40 - $.80 in cost prior to your sawing? Or is that typo?


No, the material is $0.04 per ct. So if I cut a 10 ct piece or a 20 ct piece to cut the same size finished stone, what's the difference? 40 cents or 80 cents. My time is at least $1 per minute, so I am not going to spend time to fret over 40 cents of material. Maybe for you it is, not for me.

Thanks for the clarification. But in general I think the current conversation was about something else, more like less experienced being able to adapt from the waste as you put it in the wasteland of hobby cutting to less waste when cutting more expensive materials. But like I said it's more about your time.

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