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PostPosted: Sat Sep 27, 2008 2:50 am 
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StarCutGems wrote:
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.
John


Hello John,

I tried the 2 stick juggle for my first few stones, absolute nonsense. I have been cutting and polishing a table by hand and using your transfer procedure for the past 35 years.

Cutters who cut enormous behemoth stones, those who cut itsy teensy stones and cutters of very very expensive stones use this procedure, so we are not alone. Hardly relevant but all diamond cutters do it this way too.

Tony.

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PostPosted: Sat Sep 27, 2008 3:30 am 
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"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. "

Well, you couldn't realign it in the standard sense. It's not adjustable. But it could be re-machined should it ever wear enough to require it.

"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."

I think you are referring to their table aligner. A flat square of metal on a dop stick? That's an extra. I don't own one. The table adapter that comes with the machine includes a special "T" dop that I use (I don't know what it's called but it's a round bar attached to a dop horizontally). You can also use the T dop to align your index gears when you switch them out so they are zeroed to your cheater. FYI, On my old UT the table adapter also "is" the alignment fixture.

Regarding removing the stone to transfer. I'd need to be better at getting my first dop flat to the table for that to work for me. As is it's almost never flat now. Plus, it would be hard to match it back up to the key system, if desired. (Although I don't always care for the keys and can overide as needed.) Also, it seems like recentering rectangular stones would be hard. Sperisen, in the Art of the Lapidary, has an illustration of a fixture for centering the stone. Basically a device to hold the dop stick vertical and a horizontal ruler that slides up and down on a mast so you can lower the ruler to the stone.

Steve

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PostPosted: Sat Sep 27, 2008 10:38 pm 
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jayinasia

When dopping with epoxy, there are some things to be careful about that may not be obvious.

1) Use a quick setting epoxy. I use Devcon 5 minute. Others use other brands, but everyone I know uses 5 minute. It's not really 5 minutes to full hardness, but maybe about that to where the epoxy is too think to dop with. An epoxy that takes longer to cure allows more time for errors to creep in, such as maybe the jig isn't totally level, etc. which leads to:

2) Be VERY careful that the epoxy, once the stone has been dopped, is even all around the stone. You said you make sure it's even on the dop, but when putting the stone and dop together, the epoxy can be pushed a bit to one side or another. Related to this is whether you lay the transfer jig on its side. If you do, the epoxy will run down and build up more on the bottom side that on the top. The faster it cures, the less time for this to happen. I always stand the jig on end so the dops are vertical, usually with the new dop on the bottom, so if the epoxy runs a bit, it's away from the stone so that it doesn't affect it.

3) When you mix the epoxy, you WILL get bubbles. Epoxy heats up as it cures, and the air in these bubbles will expand as it gets warmer. Wait a short while (how long? experiment) until as many of the bubbles as possible have gone away. This, combined with more epoxy on one side than on the other, is probably the main reason for tilting.

Remember that there is nothing that makes a stone tilt in only one direction, so if you see a tilt side to side, there may well be a tilt in another direction. Sometimes people allow for a sideways tilt and forget this, so the girdles on the ends are different thicknesses when this happens.

As you pointed out, nothing guarantees that the flat,where you dopped the first dop to the stone, is parallel with the girdle once you have done the pavilion. It probably is, much of the time, but Murphy's Law says that the more expensive the rough, the greater the tilt of the flat to the girdle will be. While some laws are made to be broken, this one cannot be broken as you never know when it will be applied. Assume that the flat is NOT parallel to the girdle until proven otherwise.

I have used the method StarCutGems talks about when a stone comes off the dop for some reason, but I don't do that very often, and wouldn't want to do it all the time. I know one person who does use this method and with his experience level, he makes it work. He has years and years of experience.

A very handy tool to help in that situation, or to help when dopping that piece of rough that's expensive or just important is called the Magdop. It's at www.magdop.com and it helps hold the stone so you can position it as needed. I use it and think it's very good to have around.

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PostPosted: Sun Sep 28, 2008 12:22 am 
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Bob,

Thanks for the tips on epoxy. I have yet to try epoxy but I've got a couple of nice neon blue Apatite pieces that need to get cut one day. :D

I will definitely keep your tips in mind.

I've known about the mag dop for sometime but when it comes to spending my hard earned money on a magdop or more rough I just can't refuse the rough. Yep, it's an addiction. I wish you guys would've warned me before I got back into this. :P

I'm going to give it a few more stones before I write off the Omni transfer jig completely but in the meantime I will check out the mag dop and some of the professional techniques defined above.

Thanks to all.

Jay


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PostPosted: Sun Sep 28, 2008 11:33 am 
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I would recommend a new transfer jig.

On the other hand when now and again a gem gets crooked somehow (even with a good transfer jig) and gets QUITE crooked (or falls off and gets crooked when reglued) I often pop it off the dop and redop with wax by eyeball for centering etc.

I know this sounds scary but one can become quite proficient at it and it works better for me than trying to use the rough "table" which is almost never 100% square with the girdle.

I just heat it up, attach it to the dop and stick in in the machine with the quill vertical and look at it from one side, then the other etc and try to get it looking the same from all sides as far as tilt goes. (You just spin the quill to look from various sides.)

I find that my eye has a slight prejudice to one side so from one direction the left side will look lower for example but if I spin it around that side will look higher (as it is now on the right) and the new left side will look a bit lower. When I hit this point I know that it is pretty much level. Centering is another issue but you can cut a slightly off center gem by changing you height adjustment, a crooked one will never be right.

This process should take 5 minutes or less once you get used to it.

Hope this helps, otherwise you can just call me nuts. :wink:

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PostPosted: Sun Sep 28, 2008 6:08 pm 
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TheGemDr Wrote:
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I tried the 2 stick juggle for my first few stones, absolute nonsense. I have been cutting and polishing a table by hand and using your transfer procedure for the past 35 years.


Hi Tony,
I love your terminology! "the 2 stick juggle"!
Exactly what I concluded reading the method. Why on earth would you introduce yet another cemented/adhered dop stick to the mix?
I do not have issue with transferring a stone after cutting 1/2 of it.
I do lots of repairs as I believe you do?

So if its the crown that needs attention, then the appropriate dop gets stuck to the pavilion, and off to the repair. Lets fix a cut corner octagon, (emerald cut). I use a vee dop to hold the pavilion in transfer fixture and use the "target" dop (flat dop) to sandwich this unattached as of yet stone between the two dops vee/flat. Next I use a couple drops of crazy glue to cement pavilion to vee dop. Then take the vee dop with attached stone out of transfer fixture and use epoxy to make a nice bead/connection that holds and does not move stone at all. Done. Fix crown and remove by heat and or solvent.
Same process if you use wax, and no need for the crazy glue at all. Just heat the dop and wax as the stone is pressed between the two appropriate dops in the fixture (only have wax on the side you are NOT doing the work to) keep pressed together until cold remove and cut. Rarely if Ever have I had Any issues with tilt etc. On a few rare occasions a little cheating squared it all up.
From reading these and other posts on the issues encountered in transfer of gems, a common problem that is noted or blamed is the accuracy of the transfer fixture used.
Without doubt, if you do not have a fixture that is accurate, then you will always end up with a problem that takes more time to remedy, work with/through than the actual cutting if the transfer had been "dead nuts" first time around.

I suppose there will be others, depending on the type of cutting they are doing, Competition, Repair, production, custom etc., that require more or less precision for the transfer.
So maybe the "2 stick juggle" has its place somewhere?

Just as John Dyer says
Quote:
I would recommend a new transfer jig.

On the other hand when now and again a gem gets crooked somehow (even with a good transfer jig) and gets QUITE crooked (or falls off and gets crooked when reglued) I often pop it off the dop and redop with wax by eyeball for centering etc.


So the eyeball can be accurate enough as well.
And why not! Since the vast majority of gems are first viewed by the eyeball before they are subjected to magnified scrutiny.

This is a good thread! Thanks jayinasia!
Best wishes in your transfers!
It is not really a scary problem deal, just a step in the process.
Practice and good equipment help as do decent Eyeballs!

:shock:

Regards,

John


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