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 Post subject: Cutting ovals - selecting the dop for transfer
PostPosted: Tue Dec 08, 2009 10:46 pm 
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I've never completed an oval before, so I'm not sure how to procede at the transfer.

I"ve cut a girdle and pavilion, no problem, just a little more effort than a round. But what dop to use if there's a culet? What about a keel? Do you have to do anything special to keep the stone from drooping while the adhesive sets?

I've only used wax one time - did it wrong, so the crown has a curious asymmetry. Good looking stone, but... Other than that, everything I"ve done up to now has been with CA.

Thanks in advance for any & all advice on this!

Kelley Dragon


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PostPosted: Tue Dec 08, 2009 11:05 pm 
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There are different dops for that I think, inverted cone is the usual one, but for a keel there are those v-shaped dops


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 Post subject: Cutting ovals - selecting the dop for transfer
PostPosted: Wed Dec 09, 2009 12:17 am 
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Hey Kelly glad you got your squealing problem solved. You can use any dop. I use wax to cut the pavillion then do a cold transfer using 5min epoxy, recommended by Gearloose, just mound the epoxy on or in any dop the key is to not let the stone touch the dop. The stone should only be held by the epoxy this insures a straight transfer, at least it does for me. Prior to figuring that out I struggled with lopsided transfers on far too frequent a basis. Have a good one.

Jim Doherty


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PostPosted: Wed Dec 09, 2009 12:19 am 
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Jim, awesome, two years and never dawned on me


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 Post subject: Re: Cutting ovals - selecting the dop for transfer
PostPosted: Wed Dec 09, 2009 2:29 am 
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dragonwerx wrote:
Do you have to do anything special to keep the stone from drooping while the adhesive sets?


All the other questions were answered. This one's easy - just leave it in the transfer jig while the adhesive sets.


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PostPosted: Wed Dec 09, 2009 6:30 am 
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Regarding epoxy, how do I get it OFF once the crown is cut? Is 'Attack' the only thing that works, or can I use gentle heat like I do with CA, or some (what?) other method?

best regards,
Kelley


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 Post subject: Cutting ovals - selecting the dop for transfer
PostPosted: Wed Dec 09, 2009 7:00 am 
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Once the glue has set wrap the second dop and stone with a WET paper
towel and apply a lot of heat, I use a plumbers torch, to the first dop it should drop off. If the dop doesn't drop off after about 10sec or if you smell epoxy getting hot then gently tap the dop it will drop off.
Be careful the dop that drops off will be extremely hot do not touch it
do not let it contact anything flamable.
Try it with a piece of scrap and 5 min epoxy. Make sure you use 5min epoxy the others are much stronger and diffucult to break the bond.
Thanks to Gearloose for the method.
Use the same method for removing the stone, wrap it in a wet paper towel and hold the stone with your fingers. I leave the dop in the fixture while I heat it and the stone just pulls away from the dop. Clean up the epoxy and your done.

Good luck with it, Jim Doherty


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PostPosted: Wed Dec 09, 2009 9:07 am 
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I usually, if in a hurry, will use a small sponge square with a hole in the middle to hold my stone (wet the sponge). I can use a dop holder and heat the dop to release. Then, it goes into an acetone bath for 24 hours. If it is heat sensitive, just straight into the bath and it can take up to 3 days.


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 Post subject: Re: Cutting ovals - selecting the dop for transfer
PostPosted: Thu Dec 10, 2009 10:00 am 
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Jim Doherty wrote:
Once the glue has set wrap the second dop and stone with a WET paper
towel and apply a lot of heat, I use a plumbers torch, to the first dop it should drop off. If the dop doesn't drop off after about 10sec or if you smell epoxy getting hot then gently tap the dop it will drop off.
Be careful the dop that drops off will be extremely hot do not touch it
do not let it contact anything flamable.
Try it with a piece of scrap and 5 min epoxy. Make sure you use 5min epoxy the others are much stronger and diffucult to break the bond.
Thanks to Gearloose for the method.
Use the same method for removing the stone, wrap it in a wet paper towel and hold the stone with your fingers. I leave the dop in the fixture while I heat it and the stone just pulls away from the dop. Clean up the epoxy and your done.

Good luck with it, Jim Doherty



It should go without saying, but: be careful with heating to release. A heat-sensitive stone can easily be damaged this way.

In my experience, the Devcon 5-minute epoxy bond can be broken by gentle heating -- I use an alcohol lamp. I read somewhere that the epoxy bond is only good until about 175F. That's roughly the same temp at which high-temp wax flows. (A handy tid-bit if you're used to dopping with wax.)

If you're not working with a heat sensitive stone (e.g., quartz), you could heat both the dop and the stone. I've noticed that the epoxy takes on a slightly yellow color at that point and is fairly easy to scrape off both the dop and the stone with a fingernail -- though a good acetone bath is usually necessary too.

Plumbers & butane torches are convenient, but require some finesse to ensure things don't get too hot too quickly. Nothing is worse than completing a stone only to have it ruined by too much heat when you're trying to get it off the dop. (Unfortunately, I can speak from experience here.)

peter

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PostPosted: Thu Dec 10, 2009 10:56 am 
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I use wax for the initial dopping, but since many of my stones are large or have shapes outside the range of standard dops I use a compound wax/CA for the transfer.

Use a slightly large dop and fill it with wax. Pop it into the transfer fixture and while it's warm but not runny slide the pavillion side in, then gently remove it. Basically you make a little pavillion-shaped mold for the stone. Then CA the pavillion into the wax mold. I let mine sit for an hour or so. Then wrap the pavillion join in wet paper towel and use just enough heat to remove the old wax join.

If I'm going to be cutting with a water drip, I'll also use clear nail polish around the join to protect the CA.

The large opal I just cut was CA dopped initially. After creating the wax mold, I removed the stone from the dop, and transferred it using a target dop. It seated beautifully into it's prepared dop and I didn't have to heat the stone for a wax dop or worry about weakening the new join when taking off the flat dop.

Cheers,

Lisa

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PostPosted: Thu Dec 10, 2009 1:04 pm 
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dragonwerx wrote:
Regarding epoxy, how do I get it OFF once the crown is cut? Is 'Attack' the only thing that works, or can I use gentle heat like I do with CA, or some (what?) other method?

If you want the "soak overnight" method, you can get paint stripper containing methylene chloride (the ingredient in Attack) cheaper.

Heat works. If you have a heat-sensitive stone, what I do is put it in a pan of cold water on the stove, then heat it to boiling. Let it boil a couple of minutes, then take it off the stove and let it cool down gradually. The relatively slow ramping to 210 F and back down won't stress the stone.

Caveat - this works best with 5-minute epoxy, which is not too heat resistant. Other epoxies may be reluctant to release at low temperatures. I use Devcon 5 minute, which comes in two separate 4.5 oz bottles. Enough for a year, but very convenient.


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PostPosted: Thu Dec 10, 2009 5:58 pm 
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And for the record, do not get Loctite 5 min clear. It stinks, it really comes out as yellow, not clear, the container tends to leak, the yellower agent is very stiff leading to harder to get out of the tube, and mix has to be almost perfect. Did I mention that is stinks (yes, but it bears repeating).


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PostPosted: Thu Dec 10, 2009 9:32 pm 
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Even the Devcon 5 smells terrible - it reminds me of the "permanents" my mother used to give customers in her hairdressing shop while I was growing up. The smell coming off that stuff just plain can't be good for you (the epoxy or the permanents!) I much prefer the piny smell of high-shellac wax. Sappy as it sounds, that's one of the reasons I use wax almost exclusively.

peter

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PostPosted: Thu Dec 10, 2009 11:04 pm 
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pt wrote:
Even the Devcon 5 smells terrible - it reminds me of the "permanents" my mother used to give customers in her hairdressing shop while I was growing up. The smell coming off that stuff just plain can't be good for you (the epoxy or the permanents!) I much prefer the piny smell of high-shellac wax. Sappy as it sounds, that's one of the reasons I use wax almost exclusively.

peter

Devcon 5 is roses and lavendar compared. :D


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PostPosted: Fri Dec 11, 2009 3:43 am 
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I really don't care how other cutters dop their stones as the only thing that really matters is results and whatever for whoever works, works.

I'm not adding this post to say I have nothing to add though....grin.

A typical lapidary shop is going to have a few evil things that we should all do our best to avoid ingesting and inhaling. Adequate ventilation and an 'evil' workspace in front of the extraction fans will keep us all around longer. There's few enough of us as it is.

Tony.

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