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 Post subject: Stone alignment while cutting table
PostPosted: Fri Aug 11, 2017 9:39 pm 
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I do not know why I have not done this before. I decided to cut and polish the table before I finished cutting the crown because of some issues with the lack of material on the crown. I wanted to maximize the stone. I had already started cutting the crown when I realized this issue. To keep the alignment I put the alignment jog on the dop and then cut and polished the table with it on the dop. This made aligning the stone a breeze when finished the table. I think I am going to use this technique a lot going forward. Many times after cutting the table I need to tweak something on the crown. This will help. I hope this makes sense and helps someone else.
Alex Edwards


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 Post subject: Re: Stone alignment while cutting table
PostPosted: Sat Aug 12, 2017 3:01 pm 
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I don't understand what you did there.

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 Post subject: Re: Stone alignment while cutting table
PostPosted: Sat Aug 12, 2017 3:32 pm 
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I think... The blue 'thingy' is the jig typically used during transfer. [Attach to the dop, align the jig with the lap and an index; attach transfer dop, adjust cheater to get the jig lined up with the lap again, remove old dop.]

So the jig is just aligned with with the lap, then the dop removed and put in the table fixture with jig still attached. If you need to go back after cutting the table, the jig preserves the alignment.

Cool idea (if I'm right). I've avoided using any design that says 'cut in table before' since I couldn't think of a way to preserve alignment, and while I supposed I could hunt it down again it always seemed a bit intimidating to think about. This technique though might make it a little less frightening.

Now I just need to get one of those jigs.....


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 Post subject: Re: Stone alignment while cutting table
PostPosted: Sat Aug 12, 2017 3:49 pm 
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I have a little jig that is used to help align the stone during transfer from the pavillion to the crown. I just attached it to the dop when transferring from cutting the crown to cutting the table. Now if I need to touch up any meets after cutting and polishing the table the original alignment has been preserved so it is easy to touch up after cutting the table. Hopefully these additional pictures will help.


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IMG_1863.jpg
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IMG_1862 (1).jpg
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 Post subject: Re: Stone alignment while cutting table
PostPosted: Sat Aug 12, 2017 3:53 pm 
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Jclimactic wrote:
I think... The blue 'thingy' is the jig typically used during transfer. [Attach to the dop, align the jig with the lap and an index; attach transfer dop, adjust cheater to get the jig lined up with the lap again, remove old dop.]

So the jig is just aligned with with the lap, then the dop removed and put in the table fixture with jig still attached. If you need to go back after cutting the table, the jig preserves the alignment.

Cool idea (if I'm right). I've avoided using any design that says 'cut in table before' since I couldn't think of a way to preserve alignment, and while I supposed I could hunt it down again it always seemed a bit intimidating to think about. This technique though might make it a little less frightening.

Now I just need to get one of those jigs.....


You are correct. You explained it better that I did, THANKS! I hope the new pictures help. Here is another one with the dops in the transfer jig.


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 Post subject: Re: Stone alignment while cutting table
PostPosted: Sun Aug 13, 2017 12:19 pm 
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Thanks Alex and Robert.
I think this clamp could be considerably shorter and still accurately indicate radial alignment.

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 Post subject: Re: Stone alignment while cutting table
PostPosted: Sun Aug 13, 2017 12:48 pm 
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This alignment clamp isn't hard to make if you have machining expertise. Marsh Howard had these for sale at the last FFF. I don't know if they're part of his (MagDop) product line now.


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 Post subject: Re: Stone alignment while cutting table
PostPosted: Mon Aug 14, 2017 10:00 am 
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Keyed dops allow you to interrupt cutting cutting the crown to cut the table, and reinsert the dop correctly aligned. I do this frequently on my Ultra Tec without problems to cut the star facets. The alighment jig is useful if you don't have keyed dops or if the keying is not reliable.


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 Post subject: Re: Stone alignment while cutting table
PostPosted: Mon Aug 14, 2017 1:46 pm 
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I keyed my dops for my modified 5XL handpiece. The dops came with a hole drilled into the diameter surface. I purchased stainless steel pins to tap into the holes.

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 Post subject: Re: Stone alignment while cutting table
PostPosted: Mon Aug 14, 2017 3:32 pm 
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Duncan Miller wrote:
Keyed dops allow you to interrupt cutting cutting the crown to cut the table, and reinsert the dop correctly aligned. I do this frequently on my Ultra Tec without problems to cut the star facets. The alighment jig is useful if you don't have keyed dops or if the keying is not reliable.


I don't think I've ever used non-keyed dops - how exactly do they align?

I just finished a good sized Hartz range garnet, I had set the preform (done on a cabbing machine because of the size) on the dop with a large dollop of epoxy. When I went to start, I discovered that it had shifted on the dop - somehow turning on it's axis but not sliding or rocking - and rather than rip it off and start again I ended up deciding to calculate new index positions. Not difficult, it was a simple step cut - yes I know, a large deep-coloured stone done as a big, physically deep step cut but that's what the guy wanted, despite me saying that it would probably come out very dark, though in the end it showed more colour and light return than I had expected.

Anyway, that worked nicely until I came to put it in the transfer jig and realised that the keyed dops would not allow a vee dop to align on the keel. I ended up having to re-calculate another new set of index values and give the cheater a good twist. In the end, it came out pretty well perfect.


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 Post subject: Re: Stone alignment while cutting table
PostPosted: Mon Aug 14, 2017 3:49 pm 
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I consider keyed dops more a liability than an asset. Lefty, if your dops were not keyed, you could have easily realigned the rotated stone.


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 Post subject: Re: Stone alignment while cutting table
PostPosted: Mon Aug 14, 2017 8:39 pm 
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AlBalmer wrote:
I consider keyed dops more a liability than an asset. Lefty, if your dops were not keyed, you could have easily realigned the rotated stone.


Yeah, keyed dops seem to be something people either love or hate but I haven't used both so I can't judge.

So a keyless dop must still be somewhat different to say, a drill bit being inserted into the chuck of a drill in that something has to align it?


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 Post subject: Re: Stone alignment while cutting table
PostPosted: Mon Aug 14, 2017 8:44 pm 
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I suppose the rationale behind the keyed system is that the dop cannot turn out of alignment in the collet if it comes loose and you can pull a dop out if for some reason you have to stop part way through a pavilion or crown to start another and it will always go back in exactly as it came out.

But as I've just discovered, they can have their own disadvantages as well :?

Good thing it was just a simple step cut I was re-doing index value's for and not a design like "The Arkenstone of Thrain" :)


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 Post subject: Re: Stone alignment while cutting table
PostPosted: Mon Aug 14, 2017 9:31 pm 
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So a keyless dop must still be somewhat different to say, a drill bit being inserted into the chuck of a drill in that something has to align it?

No, the dop doesn't need to be aligned, the stone needs to be aligned. Once you've cut a facet, the stone is aligned to the lap. After transfer, you align a facet to the lap. I'll send you a writeup with specifics.


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 Post subject: Re: Stone alignment while cutting table
PostPosted: Tue Aug 15, 2017 4:58 pm 
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At one time Graves made little shaft collars with a radial bump machined in them. This engages with the groove on the quill. They made any 1/4" dop into a keyed dop and worked quite well. I have no idea if they still sell them. It may have been too good an idea to bother making.

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