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 Post subject: Re: Jam Peg Video
PostPosted: Wed Dec 15, 2021 1:40 pm 
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Steve I think what you many not understand is that people using meetpoint cutting also think a bit about what why are doing so as to not waste material. If I were to cut a round design with several tiers of facets on the pavilion, say 50, 45, 42 39. I wouldn't cut the 50 degree facet to a point. Then keep cutting that point away with each tier. I use a Gem Master, so I can cut a very accurate depth, so cutting the 50 degree tier I would not cut to a point, not even close, I would cut it to a depth so that by the time I finish with the last tier I just run out of stone and form a point.
I can't picture if you were preforming a round very close to the finished shape, and just laying in facets almost with a polish you would achieve any higher yield than the method I use. I would spend a lot less time preforming, and would most likely have the pavilion fully cut before the accurate preform method would be done preforming. I'll fully cut a round stone in under an hour, to very high precision standards.

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 Post subject: Re: Jam Peg Video
PostPosted: Wed Dec 15, 2021 3:00 pm 
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Gene, I do not think I understand your answer or explanation here. How do guarantee that when you get to your CP tier of 39 degrees you have enough rough left to adequately place an appropriate size facet? Or is it just whatever is left is what it is? Or do you reverse back up the tier levels to adjust for that tier? Or, or, or?

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 Post subject: Re: Jam Peg Video
PostPosted: Thu Dec 16, 2021 12:01 am 
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Precision Gem wrote:
Steve I think what you many not understand is that people using meetpoint cutting also think a bit about what why are doing so as to not waste material. If I were to cut a round design with several tiers of facets on the pavilion, say 50, 45, 42 39. I wouldn't cut the 50 degree facet to a point. Then keep cutting that point away with each tier. I use a Gem Master, so I can cut a very accurate depth, so cutting the 50 degree tier I would not cut to a point, not even close, I would cut it to a depth so that by the time I finish with the last tier I just run out of stone and form a point.
I can't picture if you were preforming a round very close to the finished shape, and just laying in facets almost with a polish you would achieve any higher yield than the method I use. I would spend a lot less time preforming, and would most likely have the pavilion fully cut before the accurate preform method would be done preforming. I'll fully cut a round stone in under an hour, to very high precision standards.



I am not saying that a cutter will not think his stone through carefully before choosing a pattern and cutting. However in your description, if you are starting with the 50 degree cut at the girdle then you are not using the classic meet point system of cutting. You are likely shaping the stone at the girdle line. The shape of your stone which I presume is chosen to give the maximum diameter from the rough, and the depth of available material is controlling the stone cut.

In the classic meet point style you would be cutting the 39 degree tier to a point as the first step, then cutting each tier down to the girdle line. Then cutting a level girdle to create the stone outline. In order to make it work, you need the stone perfectly centered on the dop.

A you can see from this introduction to the classic meet point faceting system video everything is being controlled by a chosen angle that is being cut to the center of the stone, which because mast height remains constant is also the center of the dop. That point, angle, and the smallest radius from the center of the dop is controlling the ultimate diameter (and thus yield) of the stone. In this video they are cutting the simplest RBC. Because of the nature of the RBC the detrimental impacts of this system are the most minimum they will ever be. Once shapes become more complex the impacts are much larger, resulting in even less flexibility, and even smaller diameters and yields.

If you do take the third option you are still required to shape the stone by cutting the 90 degree girdle facets an exact equal distance from the center of the dop. If not, the points where three facets meet will never line up properly. You are forced into letting the pattern and predefined angles control the stone. No ability to adjust to stone problems.

The video: https://www.youtube.com/watch?v=qZOFBAFzl9k&t=75s

It is much more efficient to develop a hybrid system that still allows precise meets, without depending on centering and cut depth to set the meets, and allows for on the fly angle adjustments to accommodate issues in the rough.

If you are talking about cutting an SRB to pre-determined angles I think any approach will allow a finished stone in an hours time. In such stones time is more about knowing you machine and laps to create a process to a predictable perfect polish with the fewest visits to each facet. Time differences are not large when cutting 2 carat stones. But when cutting large stones removing the bulk of material on a preforming machine save huge amounts of time. Then you are just laying on the facets with a fine lap, and polishing. I often do this with a two zone lap. Each facet is only touched twice. Each time measured in seconds. You must also being doing something that efficient as well. An SRB has 57 facets. In order to cut in an hour you must keep total time per facet to under a minute.


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 Post subject: Re: Jam Peg Video
PostPosted: Thu Dec 16, 2021 5:30 am 
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Does nobody have an answer to my question why the peg board in the jamb peg video has diagonal rows of holes instead of just a single column of holes, when the entire board can be tilted to change the angle? I think I understand the curvature of the board - to accommodate much steeper or shallower angles without having to move the post relative to the lap spindle, if I am correct - but not the multiplicity of holes.


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 Post subject: Re: Jam Peg Video
PostPosted: Thu Dec 16, 2021 12:09 pm 
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Certainly in meetpoint cutting the stone is centered on the dop. But as Duncan pointed out, if using wax, it's very simple to nudge the stone if you find it's not centered. I would think that working with an off center stone and a mast machine would be constantly adjusting the slightly the mast height for each facet. If you can eyeball a round profile on an offset dopped stone, I would think you could eyeball put the stone centered on the dop.

As far as the classic meet point cutting as shown in Long & Steele you are working from the girdle to the culet as shown in their drawings.

Image
Image
Image

What I am saying is it's not always necessary to cut that first tier to point.

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 Post subject: Re: Jam Peg Video
PostPosted: Thu Dec 16, 2021 12:11 pm 
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glhays wrote:
Gene, I do not think I understand your answer or explanation here. How do guarantee that when you get to your CP tier of 39 degrees you have enough rough left to adequately place an appropriate size facet? Or is it just whatever is left is what it is? Or do you reverse back up the tier levels to adjust for that tier? Or, or, or?


Sometimes you come up short and need to recut from the first tier. After this happens to you a few times you get pretty good at judging by eye how sharp of a point you need to form to have the final tier close to a point.

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 Post subject: Re: Jam Peg Video
PostPosted: Thu Dec 16, 2021 1:36 pm 
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Looking at the process as shown in the pictures, it looks to me like you are still cutting to the center point on the dop, then cutting to a level girdle to establish the outline. This is true whether or not you are cutting the first tier and don't actually close culet. If you were cutting fully to the culet tip at the girdle tier angle that would be even more wasteful.

In either case your outline maximum diameter is defined by the center of the dop and the angle you choose. That on average will cost yield.

The exception for me is in cases where the depth of the rough is the limiting factor. It is this depth that must define the maximum diameter if you are committed to not ending up with a window in the stone, and the pattern doesn't allow you to create a "soft" window by staggering (interlacing) the last two rows.


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 Post subject: Re: Jam Peg Video
PostPosted: Thu Dec 16, 2021 1:48 pm 
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I have recently been working on a project that may turn out to providing some points of references between cutting methods and styles. I have been making metal molds of natural stone rough. I then cast high RI glass in the molds to create simulated rough. This way students all start with an exact piece of rough so that their results can be properly compared and evaluated. Each piece of rough I am doing this for is chosen to demonstrate a particular shape, pattern, or problem, in cutting. My goal is to end up with somewhere near 24 roughs, and 4 or 5 damaged cut stones to teach re-cutting methods.

When i get it done, maybe we can each try our methods to see actual comparative results. It is my guess that in the simple shapes and patterns the differences between highly skilled cutters will be close. But in larger, more complex pieces, the differences will be larger. Interesting experiment.


Making molds to experiments with cutting very expensive larger rough like Ruby is becoming more common in some of the cutting centers. they give the molded rough to different cutters to see who comes up with the best solution before cutting the actual rough. In diamonds a virtual solution to this has been implemented for some time now using the Sarine style 3D scanner/plotter type solutions.


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 Post subject: Re: Jam Peg Video
PostPosted: Thu Dec 16, 2021 3:08 pm 
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1bwana1 wrote:
Looking at the process as shown in the pictures, it looks to me like you are still cutting to the center point on the dop, then cutting to a level girdle to establish the outline. This is true whether or not you are cutting the first tier and don't actually close culet. If you were cutting fully to the culet tip at the girdle tier angle that would be even more wasteful.

In either case your outline maximum diameter is defined by the center of the dop and the angle you choose. That on average will cost yield.

The exception for me is in cases where the depth of the rough is the limiting factor. It is this depth that must define the maximum diameter if you are committed to not ending up with a window in the stone, and the pattern doesn't allow you to create a "soft" window by staggering (interlacing) the last two rows.


Maybe we are not understanding each other. What I am saying is don't cut the false culet to a point.

I think what you are saying is don't cut a perfect circle for the girdle. Follow the rough and let the stone not be perfectly round. So maybe you end up with 3.4 ct not round stone, and I end up with the 3.3 ct. round stone.

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 Post subject: Re: Jam Peg Video
PostPosted: Thu Dec 16, 2021 4:28 pm 
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Lol, this is not pros and cons of JP v MP. To boot, all over a RB. Not even about the topic any more. What are the advantages or disadvantages cutting a RB on the Peg or the mast.
Duncan, I attended a couple jamb peg instructional demonstrations several years ago in Los Angeles with an experienced tradesman, if I am remembering correctly the columns are as you stated but as well accommodate stone sizes and rows were used as mostly as lap placement and somewhat cheat system. But all being wood and wear occurring relatively fast, gained experience by the cutter knew which pegs to use to gain the achieved placement of a facet. He stated that many well experienced jamb peg cutters prefer the quills and boards of their own. I always saw it just like on my machines and laps I know where and what to expect based on where the mast is positioned, swiveled in or out. I do not believe based on his demonstration there was a definitive answer. Just like this thread has exposed, we like what we like and we do it the way we feel comfortable.
I tend to follow Steve's process to a point in general the majority of the time, but as well understand that whether a design is followed by the tee or improvised on the fly based on individual rough characteristics, I find a well thought out preform for me limits the back tracking on tier adjustments to accommodate misjudgements of required proportions and problem areas. Again not about jamb peg cutting.

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 Post subject: Re: Jam Peg Video
PostPosted: Fri Dec 17, 2021 12:08 am 
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The video and skills are fascinating, and the current discussion interesting. I want to put some issues into perspective. I would expect an establishment like Arnoldi (and similar from Idar Oberstein) to be pragmatic and use technology where advantageous. Maybe concentrating on better quality rough? Would all stones cut by them be done on jamb peg machines? That is, large and small stones, all styles (brilliants, long steps, etc), lighter stones with multiple tiers and darker stones with single tiers. May they (Arnoldi and similar) also use modern faceting machines for certain stones? Information from their website does not answer these questions.

Thanks.


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 Post subject: Re: Jam Peg Video
PostPosted: Fri Dec 17, 2021 2:03 am 
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[quote="geowork"]The video and skills are fascinating, and the current discussion interesting. I want to put some issues into perspective. I would expect an establishment like Arnoldi (and similar from Idar Oberstein) to be pragmatic and use technology where advantageous. Maybe concentrating on better quality rough? Would all stones cut by them be done on jamb peg machines? That is, large and small stones, all styles (brilliants, long steps, etc), lighter stones with multiple tiers and darker stones with single tiers. May they (Arnoldi and similar) also use modern faceting machines for certain stones? Information from their website does not answer these questions..[/quote]

What issues are you proposing to put in perspective? Maybe you might contact them to inquire of your curiosities. If you're not finding what you need on a website.

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 Post subject: Re: Jam Peg Video
PostPosted: Fri Dec 17, 2021 3:35 am 
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That could be seen as a condescending reply, given the opinions and knowledge already demonstrated in this discussion. Also the questions were posed with consideration that others reading may have similar issues and be interested in responses. Apart from that, yes, I could contact them direct.

Regards.


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 Post subject: Re: Jam Peg Video
PostPosted: Fri Dec 17, 2021 11:13 am 
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The typical work flow in Idar these days is for larger better stones to be cut there. Almost all use the jamb peg methods for this.

The middle tier of stones in size/quality/rarity is mostly preformed and sorted in Idar. It is then commonly sent to a lower cost location for cutting.

Lower cost and small rough is often sent to these low cost centers for the entire cutting process.

These lower cost facilities may take a number of forms. They can be either owned or contracted. Often they are offices where sorting and preforming are done in house, but the faceting is sent out. There are large populations of home workers that will come into the office once a week to pick up new material and drop off last weeks productions.

Gemstone cutting has different solutions that are as diverse as the gemstones themselves. It is actually a very fascinating business, from sourcing, manufacturing, and selling. A unique blend of industry, artistry, and history.


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 Post subject: Re: Jam Peg Video
PostPosted: Fri Dec 17, 2021 3:00 pm 
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I did notice at some of the stations in the video, mast like components as well as the peg boards.
I believe this recent post is only antagonistic with no real interest in quality cutting centers.

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