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 Post subject: about the 7º rule for topaz
PostPosted: Fri Aug 24, 2012 9:17 am 
Just curious, after I create a new surface 7 degrees off the cleavage plane, should that new surface then be the crown side of the new stone, or does it matter?


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 Post subject: Re: about the 7º rule for topaz
PostPosted: Fri Aug 24, 2012 7:29 pm 
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I don't know about a rule, but polishing a topaz table parallel to a cleavage plane would probably result in flaking, chipping, chattering or some other faceting undesirable.

7 degrees is probably the minimum to avoid the undesirable. Table orientation will probably depend on the rough and the " minimal rule."


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 Post subject: Re: about the 7º rule for topaz
PostPosted: Sat Aug 25, 2012 4:23 am 
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Joined: Thu Jun 03, 2010 1:49 pm
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Location: South Africa
Yes, that should be the table.


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 Post subject: Re: about the 7º rule for topaz
PostPosted: Sun Aug 26, 2012 2:14 am 
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Joined: Thu Jun 03, 2010 1:49 pm
Posts: 331
Location: South Africa
Nickarnight,

To be a little more clear, the table is best about 8 degrees off the cleavage plane, this will ensure that none of your crown facets are at an angle that would make them susceptible to cleaving should they receive a knock once set.
If you had to rotate the stone 90 degrees to facet, there would be a danger that a crown facet may end up on the plane and give you a hard time polishing.
Also not a good idea to have the girdle too near the plane either as it may cleave while being set.
An easy way to stay out of trouble is to make the plane on the rough and place it on your drawing, that way you can rotate it around to see how your rough can be orientated and still be sure of not picking up any problems.

Have fun.


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 Post subject: Re: about the 7º rule for topaz
PostPosted: Mon Aug 27, 2012 2:30 pm 
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Joined: Thu May 29, 2008 8:32 am
Posts: 1730
Location: Suwanee, GA US
And a trick from John Campbell here in Atlanta. Get a dop and a lap you don't use. Set your angle adapter to 45 degrees. Insert the dop and now change the angle to 38 or 52. Grind this 7 degrees into your dop. Now you have a dop you can mount on the clevage plane and it will put the 7 degree correction in. :)

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George Ellis
www.faceting.biz


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