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 Post subject: Tilted Stone and Transfer Fixture
PostPosted: Wed Sep 24, 2008 6:48 am 
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Hi Guys,

Reaching out for help here. I've got a stone that obviously tilted slightly during transfer. What do you pros do when this happens?

The pavilion and girdle was perfect and I'd hate to have to start over. Please help?
:lol:

Jay


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 Post subject:
PostPosted: Wed Sep 24, 2008 7:48 am 
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What did you dop with?

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 Post subject:
PostPosted: Wed Sep 24, 2008 8:40 am 
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Peter,

High Temperature Brown Wax.

Any specific reason your asking?

For the record, I've cut about 10 stones since I've gotten back into faceting and only 1 has been a real nice transfer with only minor adjustment. I have an Omni transfer fixture and I'm looking to change. The only problem is the dops are keyed with a slant at the end that slides under a cross pin in the dop arm. Of course, this is the subject for another thread.

I'm stuck with a real nice light amethyst that I know if I keep cheating will end up with no girdle so I thought I'd see who has any suggestions.

Thanks.


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 Post subject:
PostPosted: Wed Sep 24, 2008 9:02 am 
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I asked hoping you were using wax -- one of the advantages of wax is that you can soften it and move the stone to a better position.

For example: assuming you cut the pavilion first and have a large flat that will later become the table. You could put the dopped stone back into the transfer jig and on the other side of the jig, put the largest flat dop you have available. Press the two together as tightly as you can. (Examining where the stone and the large flat meet will show you how much tilt you have after the transfer). Now, gently heat the dop with the wax joint. When the wax is just pliable, press the two dops together as firmly as you can. This should square the stone to the flat dop and thus to the done/vee dop on the other side.

I've had good success with this technique, though I've found it forces me to adjust the cheater more than I normally would -- which I greatly prefer to having different depths at opposing sides of my stone!

This process takes a little bit of finesse to do well, so a couple words of caution are in order. Be careful if your stone is heat sensitive. It is very easy to overheat the dop and thus the stone. Also, when pushing the two dops together, don't use more force than you have to to square things up. If you're cutting a square or triangle, remember you have sharp facet junctions on the pavilion that could be chipped by being forced into cone or vee dop.

I hope this helps.

peter

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 Post subject:
PostPosted: Wed Sep 24, 2008 9:27 am 
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Peter,

Great suggestion! I'm cutting an approx. 5 ct light Amethyst so heat should be ok as long as I don't shock it. I'm not sure how big of a flat is left as I did start cutting the crown and adjusting over and over until I realized my folly but there should be something there to use. I will try this tomorrow.

Thanks for your help! :D

Now. Anyone know what kind of transfer fixture I can buy and use if I have Omni dops and machine? :lol:

Jay


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 Post subject:
PostPosted: Thu Sep 25, 2008 10:42 pm 
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pt wrote:
This process takes a little bit of finesse to do well, so a couple words of caution are in order.
peter


Peter,

The theory was excellent! The practice? Not so great. :lol:

My finesse is obviously lacking. I tried several times to just get the wax warm enough to move the stone but it wouldn't budge. In my fit of impatience I used too much heat and it was like I just started to dop. Anyway, long story short, I started the pavilion over. Not that much weight loss but it took some time. The next transfer had not tilt but still a lot of cheat. I really hate this transfer fixture.

Anyway, thanks again for all your help. I gotta get me some finesse.

Jay


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 Post subject:
PostPosted: Thu Sep 25, 2008 11:28 pm 
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Hi Jay,

This transfer issue has been a problem that still plagues me to this day.

Two stones ago I had my worse episode yet. I was cutting (what ended up to be a 16 carat amethyst).

I use brown wax for my initial dopping. Alls good, the pavilion is cut and I put it in the transfer block. I use epoxy for the second dop and usually leave it to set overnight.

When done, to remove the waxed dop I just pop the stone into the freezer for a minute, take it out and with a gentle tap the waxed dop pops off. Nice and easy and no mess.

Now, in this particular instance I didn't get into cutting the crown straight away but left it for a few days. Then when I went to cut it I discovered to my horror that the stone had massively tilted and got out of alignment and was over 1mm higher on one end (It was an oval). No amount of "cheating" was going to fix this. I was very glum.

Now if it was wax instead of epoxy then I probably would have been able to soften it and fix it up.

But no such luck with the epoxy. With much trepidation I bit the bullet and I took the stone off the dop!!! I knew what I was getting myself into. I then had to re-dop it with wax and then spent a good afternoon painstakingly re-aligning it. Believe me, this is NOT a trival exercise especially when you are out by a hair and you've got to figure out the correct place to tilt the stone, etc. It was a continual process of gently reheating the wax, making adjustments, checking the stone, etc.

It was a very good learning experience but not one I wish to repeat. In the end it all worked out well and I have a particular attachment to this stone as it took ALOT more effort to finish then all my others so far.

My thought is that the epoxy, when it is setting, probably exerts a pull in a certain direction due to uneven setting. I try to make the epoxy as neat and even as possible around the end of the dop where it touches the stone so as to not leave any big bulges of epoxy.

Others have told me they never have problems with epoxy and that it must be my transfer block. If that was then case then I should expect to have this problem everytime, which I don't.

Also, I am living in a place which is very hot and this heat might also affect the epoxy when it sets, especially the longer it is left before cutting.

Anyway, it is still a mystery which I haven't conclusively solved.

Cheers.

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 Post subject:
PostPosted: Thu Sep 25, 2008 11:38 pm 
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As a side note, the reason I use epoxy for my second dop is that when I use to use wax, I had continual issues transferring.

Often I would over heat things just enough that the heat flowed through the stone and would soften the wax on the first dop. Then I would usually inadvertantly bump or knock the stone thus knocking it out of alignment. I used to fear transferring a stone as I could almost guarantee I would have problems.

A friend told me he uses wax for his first dop and epoxy for the second. This completely eliminates heat as an issue, both during the transfer operation and afterwards when you are trying to take the first dop off.

With epoxy, just put the stone in the freezer for a minute, as I mentioned earlier, take it out and tap it gently... the waxed dop comes off like magic everytime.

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[url=HTTP://WWW.BESPOKE-GEMS.COM]WWW.BESPOKE-GEMS.COM[/url]


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 Post subject:
PostPosted: Fri Sep 26, 2008 12:38 am 
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Doug,

Thanks for the input. I have never tried epoxy but perhaps I'll give it a try. Definitely mistakes happen to everyone and we all learn our lessons. I'm not the type to blame the equipment but it has been documented here before that the Omni transfer fixture has some issues. The problem is the dops are keyed and quite unique so I don't know if that will translate into a new fixture.

Anyway, I haven't been faceting long and then I had to take a long break waiting on my new machine to come from the US but it's good to be back.

Hopefully, some of the expertise from the pros around here will rub off on me!

:P

Jay


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 Post subject:
PostPosted: Fri Sep 26, 2008 1:46 am 
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zellij wrote:
My thought is that the epoxy, when it is setting, probably exerts a pull in a certain direction due to uneven setting. I try to make the epoxy as neat and even as possible around the end of the dop where it touches the stone so as to not leave any big bulges of epoxy.


I think your theory is probably right. Some epoxy changes volume as it cures. OTOH if you took pains to make sure the epoxy was even, I don't know why this would happen. Is it possible it wasn't completely mixed? I've never encountered the problem. Unless I get lucky and the epoxy just fills the dop evenly, I usually wipe it to make sure it's even. Also, I usually end up leaving the stone clamped in the transfer fixture until I'm ready to cut. That might help keep it from shifting.

I've heard of problems with epoxy softening slightly when the other dop is heated, but since you use cold instead of heat, that can't be a factor.


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 Post subject:
PostPosted: Fri Sep 26, 2008 1:57 am 
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jayinasia wrote:
Doug,

I'm not the type to blame the equipment but it has been documented here before that the Omni transfer fixture has some issues. The problem is the dops are keyed and quite unique so I don't know if that will translate into a new fixture.


The Omni key is strange, but should work OK in a conventional fixture if you're careful not to clamp on the flat. The dop diameter is strange, too, but should be OK in a v-block transfer fixture.

I've been very happy with the Polymetric transfer fixture, though you might think it pricy at $85.00.


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 Post subject:
PostPosted: Fri Sep 26, 2008 2:09 am 
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Al,

Thanks for the tip. I will definitely check it out. I figure if bad transfers cost me time and more material being cut away to fix them, then the money spent would be well worth it in the long run!

After reading further, it seems the old Omni transfer fixture was one solid block and I can't for the life of me understand why they changed it (cost?). If anyone has an old one lying around unused (i think was back when they made them in blue), I'd love to buy it.


Jay


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 Post subject: Transfer Fixture
PostPosted: Fri Sep 26, 2008 2:15 am 
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It sounds like your dops are keyed like the Ultra Tec dops with a 45 degree slant on the back. I think the Omni switched to this format from the flat key system. If so, in that case Ultra Tec's Transfer Fixture would work since it's designed for that key system. But cost wise it makes the Polymetric look cheap. List is $235. It's machined from a solid billet of aluminum with no moving parts so it's rock solid. The dops are slide together using little pushers and just slide in the V groove.

I hardly ever use epoxy (no patience) but an article I read by Charles Covill at the USFG site indicates epoxy shrinks as it cures. Two tips he gave were to put a dab of vaseline in the bottom of the dop and to mix in a bit of cream of wheat with the epoxy. It cushions and provides room for expansion and contraction. Here is the link: http://www.usfacetersguild.org/articles ... adhesives/ I did try it once and had no issues.

BTW, I often use the system where you make an impression in the wax for transfer and then glue with super glue. Less heat involved. This works pretty well but even so transfers are still the hardest thing for me.

Hope this helps,

Steve

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 Post subject:
PostPosted: Fri Sep 26, 2008 1:28 pm 
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Hi,
Being a self taught faceter, with zero exposure for the first several years to any other live lapidaries, (only lapidary journal & Faceting for Amatures by Vargas), I have never had a stone dopped (waxed or glued at both ends) between two dop sticks to accomplish a transfer.
The machine I started with, Facetron, came with a transfer fixture, and a "target dop" (large flat aluminum "bulls eye" stuck to a dop stick which fit into transfer block.)
So I cut the pavilion of lets say a round brilliant, then removed the half done stone from dop, placed the pavilion in a cone dop with wax or epoxy and slid the flat to the target dop flat gave it a tight press and transfer done. Same with vee transfer. For keel pavilions.
Never an issue with tilts or much else. maybe a tad of cheat, however nothing that was a pain or detriment.
Only now with reading & (paying attention) to these posts have I visualized that there is another way to transfer stones!
Seems like more work to me, and from many of the posts a very problematic issue.
I suppose whatever works for a person is the best way to go or continue.


Regards,
John


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 Post subject: Re: Transfer Fixture
PostPosted: Fri Sep 26, 2008 4:33 pm 
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Silverborn wrote:
It sounds like your dops are keyed like the Ultra Tec dops with a 45 degree slant on the back. I think the Omni switched to this format from the flat key system.


If that's the case, I approve of the change. The flat key looked pretty iffy to me, and even Jeff Graham said it wasn't very accurate.

Quote:
If so, in that case Ultra Tec's Transfer Fixture would work since it's designed for that key system. But cost wise it makes the Polymetric look cheap. List is $235. It's machined from a solid billet of aluminum with no moving parts so it's rock solid. The dops are slide together using little pushers and just slide in the V groove.


Wow! I confess that it reminds me of the "focus-free" binoculars, which really doesn't mean there's never a need to focus, it just means you can't even if you want to :-) I've never had the Polymetric get out of alignment, but if it did, it could be realigned.

Anyway, interesting information. I've never seen an Ultratec fixture up close, and the pictures in the brochure don't show much detail.

Their table alignment method seems odd. Does it work well? The Graves table attachment *is* the alignment fixture. That's the only one I've ever used.


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