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 Post subject: Choosing correct cone dop
PostPosted: Thu Jan 04, 2018 4:20 pm 
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I was in the process of doing my first transfer. I'm cutting the GEM101 from Tom's book. I was reading that you wanted the cone dop to be just a bit smaller than the stone. The Facetron has a 1/4" and 3/8" dop, but nothing between them. The picture is a little deceiving, but the 3/8" dop is just a little larger than the flats on my stone. But the 1/4" looked way too small. I went ahead and used the 3/8" dop since I wasn't doing anything with the girdle and I didn't think it would hit the lap (which it didn't and I cut/polished everything OKish). But I was concerned that there wouldn't be a good epoxy "joint".

This is more FYI for my next cut, but should I have went with the 1/4" or did I make the correct decision? Thanks!
Dave

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 Post subject: Re: Choosing correct cone dop
PostPosted: Thu Jan 04, 2018 4:23 pm 
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I'll also include the finished stone since I don't think this fits the awesomeness of the "Off the dop" post!

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 Post subject: Re: Choosing correct cone dop
PostPosted: Thu Jan 04, 2018 8:28 pm 
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You're good. As long as there's no chance of the dop contacting the lap, it's fine, and more secure than the smaller dop.

Pretty stone.


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 Post subject: Re: Choosing correct cone dop
PostPosted: Fri Jan 05, 2018 12:24 am 
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You did a great job Dave and your gem certainly belongs in the 'off the dop' thread. We are all friends here. Regarding your question I think it depends on your choice of dopping method. If using epoxy I would use the smaller one and buttress the glue to give it some extra strength. If using wax and superglue method (say for more heat sensitive stones) the bigger one definitely. As Al said as long as the dop is not contacting the lap you are golden.


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 Post subject: Re: Choosing correct cone dop
PostPosted: Fri Jan 05, 2018 9:54 am 
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Thanks Al & Jamie.

Jamie, I am using 5 minute epoxy. I thought about using the smaller dop and building up some epoxy around it as you mentioned. I got a little worried though and decided the bigger one would work. But after removing the stone from the cone I was really surprised by how little epoxy there was between the dop and stone. I guess trusting your choice of adhesive comes with time! I'm also guessing that after a few stones I'll feel a little more comfortable with experimenting.

Thanks again
Dave


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 Post subject: Re: Choosing correct cone dop
PostPosted: Fri Jan 05, 2018 12:18 pm 
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I would have used the larger dop, but be careful so that you don’t have too much epoxy in the cone so that it covers up over the girldle as this will make it hard to see the girdle thickness when cutting the crown.

You may want to try wax on the first dop, then epoxy on the cone. This way removing the dop after transfer is very simple and quick with just a little heat applied to the dop with the wax.
Another advantage of wax is that once you start cutting, and you see that the stone isn’t centered properly, you can heat it a bit, and shift it.

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 Post subject: Re: Choosing correct cone dop
PostPosted: Sat Jan 06, 2018 7:07 pm 
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Gene is spot on in everything he said and that is how i do my stones. Wax on pav and epoxy crown. I was told to try to use a cone about 2/3 the size of the pavilion. Would like to hear others input on this.
I hear Devcon is a good epoxy over there in the States. We don't get it here in Australia so I use a product called Dextone. Never had an issue with it.


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 Post subject: Re: Choosing correct cone dop
PostPosted: Sun Jan 07, 2018 10:25 am 
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Precision Gem wrote:
I would have used the larger dop, but be careful so that you don’t have too much epoxy in the cone so that it covers up over the girldle as this will make it hard to see the girdle thickness when cutting the crown.


Thank you for this observation as it is a really good one and bears repeating. I had epoxy all over the girdle on the stone and fought it the whole time. I will have to look into using wax also. I can see the benefit of using it first to make quick adjustments.


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 Post subject: Re: Choosing correct cone dop
PostPosted: Sun Jan 07, 2018 11:29 am 
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Precision Gem wrote:
be careful so that you don’t have too much epoxy in the cone so that it covers up over the girldle as this will make it hard to see the girdle thickness when cutting the crown.

Good point. I learned this the hard way so long ago it didn't occur to me to mention it. I usually use an alcohol-dampened bit of paper* to wipe the joint before taking it off the transfer jig.

*Actually, I use Kimwipes - they don't leave stray paper particles.


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 Post subject: Re: Choosing correct cone dop
PostPosted: Sun Jan 07, 2018 7:38 pm 
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There are a couple of good reasons to use the smaller cone dop.

A common problem when dopping with epoxy is getting the epoxy on the culet. Often when removing the stone once it is finished folks will pry the epoxy off of the stone once it is released, assuming here that the dop was heated to decompose the epoxy as most people I know do. The culet is the weakest part of the stone and sometimes comes off with the epoxy. Very frustrating!!

With the smaller dop, the culet is a bit less likely to have the epoxy reach it, when doing the transfer, hence a smaller chance of it breaking off. With the larger dop the stone sets deeper in the dop and is a bit more likely to be covered with epoxy, and the epoxy is close to or on the girdle.

What I do and teach is to drip epoxy into the cone dop until a meniscus forms. When pushing the stone into the cone dop the epoxy forms a ring/donut around the stone and dop edge. Lift the transfer jig up so the receiving dop is vertical and on top. Let the epoxy run a little onto the stone, about 10 seconds, then set the transfer jig down on a surface with the receiving dop on the bottom and leave it there for a hour.

Doing it this way most always results on a culet free of epoxy.

Understand that the smaller cone dop is the same size as the initial dop. It has more holding power than you will need. Also, as the dop and epoxy in it are not as wide as the stone, the likelihood of getting epoxy on the girdle facets is eliminated.

Years ago I was told by a multiple national contest winner that one should always use a smaller dop. Also, to heat the dop twice as long as the first dop to ensure that the epoxy is coming apart/losing it's grip on the stone.

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 Post subject: Re: Choosing correct cone dop
PostPosted: Mon Jan 08, 2018 2:26 am 
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Facetor wrote:
A common problem when dopping with epoxy is getting the epoxy on the culet. Often when removing the stone once it is finished folks will pry the epoxy off of the stone once it is released, assuming here that the dop was heated to decompose the epoxy as most people I know do. The culet is the weakest part of the stone and sometimes comes off with the epoxy.
Another good reason to use wax. :twisted:

Some recommend putting a small blob of vaseline on the culet before transfer to prevent epoxy from sticking to it.


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 Post subject: Re: Choosing correct cone dop
PostPosted: Mon Jan 08, 2018 1:55 pm 
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Agreed all reasons why learning to dop with wax. It only hurts when it hits the skin and only for a few seconds. Much better than all the time spent getting a stone out or off with epoxies. Super glue can even be friendlier.
Greg

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