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 Post subject: Re: Stone alignment while cutting table
PostPosted: Wed Aug 16, 2017 1:36 am 
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Keys for different machines vary. On a modern Ultra Tec the key consists of a simple 45 degree bevel on the back end of the dop, which rests against a fixed transverse rod in the quill. This means any 1/4" dop can be provided with a key by grinding a 45 degree bevel on the end. The angle doesn't even have to be very accurate. If you don't want to use the key, you just rotate the dop off the rod. V-dops don't need keys because the stone is re-aligned easily using a long girdle facet.

When cutting ovals and pears you may want to orientate your rough initially in accordance with the key, to facilitate a keyed transfer later. If you dop with glue you can use a keyed transfer block to help you orientate the stone. Dopping with wax, you can heat the dop in the quill gently and adjust the orientation of the stone before cutting.


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 Post subject: Re: Stone alignment while cutting table
PostPosted: Wed Aug 16, 2017 4:34 pm 
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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.


Thanks Al, that'd be interesting. I appreciate it. Cheers.

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Keys for different machines vary. On a modern Ultra Tec the key consists of a simple 45 degree bevel on the back end of the dop, which rests against a fixed transverse rod in the quill. This means any 1/4" dop can be provided with a key by grinding a 45 degree bevel on the end. The angle doesn't even have to be very accurate. If you don't want to use the key, you just rotate the dop off the rod. V-dops don't need keys because the stone is re-aligned easily using a long girdle facet.

When cutting ovals and pears you may want to orientate your rough initially in accordance with the key, to facilitate a keyed transfer later. If you dop with glue you can use a keyed transfer block to help you orientate the stone. Dopping with wax, you can heat the dop in the quill gently and adjust the orientation of the stone before cutting.


Hi Duncan. The VJ keyed dops are like the Ultra Tec dops, just a 45 degree bevel on the end.

I'm not sure what you mean by rotating the dop off rod - the dop will not insert all the way home into the quill of my machine in any other position. I'm guessing you just mean don't push it all the way home? I typically put the dop in the quill and gently rotate it until it finds the slot/rod whereby it sinks into position. Usually, it gently pushes back out a bit with compressed air before sinking right down, indicating a very neat fit I guess. I think the chuck would still tighten up and hold the dop firmly in the quill even if it wasn't pushed right the way home.

Cheers


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 Post subject: Re: Stone alignment while cutting table
PostPosted: Thu Aug 17, 2017 1:55 am 
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Lefty wrote:
Hi Duncan. The VJ keyed dops are like the Ultra Tec dops, just a 45 degree bevel on the end. I'm not sure what you mean by rotating the dop off rod - the dop will not insert all the way home into the quill of my machine in any other position. I'm guessing you just mean don't push it all the way home? I typically put the dop in the quill and gently rotate it until it finds the slot/rod whereby it sinks into position. Usually, it gently pushes back out a bit with compressed air before sinking right down, indicating a very neat fit I guess. I think the chuck would still tighten up and hold the dop firmly in the quill even if it wasn't pushed right the way home. Cheers

Hi Lefty - By 'rotating the dop off the rod' I mean inserting the dop so that the bevel does not align with the rod. This does mean not inserting it all the way home in the quill, so your chuck will have to prevent the dop from rotating in use. (The modern UT differs from the VJ in having a small air-bleed hole in the quill to avoid the compressed air issue, and the dop is held in the quill with a set screw rather than a jawed chuck.)


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 Post subject: Re: Stone alignment while cutting table
PostPosted: Fri Aug 18, 2017 9:07 pm 
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I bypass all these problems by cutting my table without the adapter by setting my mast to 0 degrees. Everyone on this forum has told me not to but I've done it every time with success. You just have to be super slow and careful but it makes things so easy when you can cut the table before prepolishing or enabling you to jump back and forth as you please without worrying about alignment or spending lots of extra time setting up a table adapter.

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 Post subject: Re: Stone alignment while cutting table
PostPosted: Sat Aug 19, 2017 3:40 am 
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justinkprim wrote:
I bypass all these problems by cutting my table without the adapter by setting my mast to 0 degrees. Everyone on this forum has told me not to but I've done it every time with success. You just have to be super slow and careful but it makes things so easy when you can cut the table before prepolishing or enabling you to jump back and forth as you please without worrying about alignment or spending lots of extra time setting up a table adapter.
I also often do this when cutting smaller stones, but use the table adapter to polish.


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 Post subject: Re: Stone alignment while cutting table
PostPosted: Sat Aug 19, 2017 4:21 am 
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justinkprim wrote:
I bypass all these problems by cutting my table without the adapter by setting my mast to 0 degrees. Everyone on this forum has told me not to but I've done it every time with success. You just have to be super slow and careful but it makes things so easy when you can cut the table before prepolishing or enabling you to jump back and forth as you please without worrying about alignment or spending lots of extra time setting up a table adapter.


Yes, I've never had a problem with that either. I've never owned an adaptor and I've never once had the stone seriously snag on the lap while either cutting or polishing the table.


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 Post subject: Re: Stone alignment while cutting table
PostPosted: Tue Aug 22, 2017 2:05 am 
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Gearloose wrote:
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.


I will take dozen. Please?
:) It might fix tons of alignment problems I have.


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 Post subject: Re: Stone alignment while cutting table
PostPosted: Tue Aug 22, 2017 12:17 pm 
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on my Gemaster II I cut and polish the tables always set at 0 degrees, never use the 45 degree adapter. When polishing I will free spin the quill.

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