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 Post subject: Assorted faceting questions
PostPosted: Fri Nov 07, 2014 7:56 pm 
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Joined: Sat Oct 25, 2014 11:42 pm
Posts: 135
Hello guys,

I have a couple of assorted questions about faceting. I thought of posting separate topics but I didn't want to flood the forum with random questions.

1) My facetron machine (pre 2003, no dial indicator) seems to be way off in the degrees measurements with respect to the hard stop. At 0 degrees it is off by 1.3 degrees, at 45 degrees it is off by 2 degrees, and at 90 degrees it is off by 1.7 degrees. I am slightly baffled by this and am wondering if there is anything i can do to recalibrate it without having to send it back (they never answered any of my emails anyways). I can recalibrate it to an extent using the little black screw on the bottom but if i adjust for the inaccuracies at 45 degrees, I end up bottoming out the screw against the gear and if i change the angle either way more than 20 degrees the rack inside ends up grinding against the gear and screw. Any ideas on how to fix this that I'm missing?

2) I am cutting CZ, sometimes when prepolishing a facet I end up with a way better prepolish than any of the other facets. Almost a milky/clear finish versus the normal smooth finish on every other facet. It seems to happen randomly but consistently (I thought it was my lap loading up and only exposing a little diamond causing this but even after a thorough cleaning of the lap and another round of prepolishing across all the facets of that tier, the same result). I suspect this has something to do with the crystal orientation of the stone? Anyone know?

3) During polishing, after I get my angles just right and the facet now sits flat against the lap, I noticed that my facets always polish from the outer most extremes inside. For example, if i had a triangular facet, the three corners would start polishing first and the polish would advance uniformly inwards. I thought that either my prepolish lap or polishing lap were slightly curved form wear which would mean the curve must be along the radius. However if i orientate my stone such that each one of the facets are at a different radius and hold it there I still end up with the polish advancing inwards from all three corners...this is baffling to me because it means that neither laps are curved, at least not in the radial direction. Anyone know whats going on?

Thanks,
-Faken2


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 Post subject: Re: Assorted faceting questions
PostPosted: Fri Nov 07, 2014 8:42 pm 
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Joined: Sun Oct 29, 2006 11:43 pm
Posts: 514
Location: North Carolina
Faken2,

How do you measure 'way off in the degrees measurements '?

Also, the Facetron with the match needle is a soft stop machine, where one matches the needles, not a hard stop.

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Bob K.


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 Post subject: Re: Assorted faceting questions
PostPosted: Sat Nov 08, 2014 1:29 am 
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Joined: Sat Oct 25, 2014 11:42 pm
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Facetor wrote:
Faken2,

How do you measure 'way off in the degrees measurements '?

Also, the Facetron with the match needle is a soft stop machine, where one matches the needles, not a hard stop.


I put my 6" aluminum master lap onto the spindle and attached the 45 degree attachment and loosened the index gear so it was free spinning. I lowered the micrometer adjustment while slowly sweeping the 45 degree attachment back and forth over the lap until it touched the lap along a line (the index is free spinning so i let it level out until it bottomed out on the edge). I slowly changed the angle and lowered the micrometer, while still sweeping the attachment, until it settled on the flat bottom of the attachment against the lap. The reading at this point was 47 degrees.

I did the same procedure at 90 degrees with a 1/4" dop, using the edge as the flat bottom and again at 0 degrees with a target dop.

I really only first noticed that my angles were off when I was doing a stone in which the girdle was cut on one side but couldn't be polished until I transferred it. When i set my angle to 90 degrees to polish the second time i noticed that my facets were not at 90 degrees.

Hmm, so the Facetron is a soft stop machine...didn't know that...yup, I'm a newbie at this. I was wondering why the "hard stop" seemed so springy. Either way, the needle indicator is toast...it was opened up before and "adjusted" by the previous owner...it doesn't work anymore. At the moment I'm cutting by ear, listening to when my lap stops cutting because even thought the machine is soft stop, there still is a stop where the quill will rest on the stop...how accurate this is? not very...


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 Post subject: Re: Assorted faceting questions
PostPosted: Sat Nov 08, 2014 2:27 am 
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Joined: Sat Jul 14, 2012 5:11 pm
Posts: 657
It is your eyes that you should be checking the facet meets with.
Barry.


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 Post subject: Re: Assorted faceting questions
PostPosted: Thu Feb 12, 2015 9:01 am 
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Joined: Sun Feb 01, 2015 9:57 pm
Posts: 66
No, maybe there's something to learn from Barry! I'ma put it on my Christmas list for next year.

Lets see here
So far

-The ability to hear facet meets.
-Another Cat's Eyelashes effect in my glass rings.(workin on reproducing)
-Get Extra Gum to start making Lemon Bar Flavor again
-For Dalan Hargrave to respond to my email so I can buy his concave faceting book


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 Post subject: Re: Assorted faceting questions
PostPosted: Wed Jun 17, 2015 10:00 pm 
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Joined: Tue Jun 16, 2015 11:12 pm
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I have seen this happen to 2 amethyst recently. They where polished with different laps so I'm thinking it's the stones. When it first happened I thought it looks like the facet is concave, but that's not logical. How could it be concave if you are sweeping the facet during pre polishing. Does anybody have any thoughts on this?


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 Post subject: Re: Assorted faceting questions
PostPosted: Thu Jun 18, 2015 4:13 pm 
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Joined: Tue Jul 02, 2013 9:00 am
Posts: 1322
Location: Wylie Texas but in Alaska for a while
I am glad you found us. Personally I wold put the questions in separate posts, that =way one part does not overtake he thread.

BUT THAT IS JUST ME

As far as CZ and one face that is different, you are correct it has to do with the material. You will find that many materails (including diamond) have a facet that reacts differently. The ony thing you can do is to try and memember that facet, and treat it gently. Many times you find this by overcutting the face, because it cuts differently.

As far as polising from 3 points to the center...... you have me scratching my head on that. MANY MANY TIMES I have had a polish walk across the face. This is usually a result of height or index mismatch between the laps.

One thought, especially on CZ, which is pretty hard. What cold be happening is that the corners are getting polished first because of the pressure. You did not mention how you were polising (very dry lap or thick slurrey). if it is a slurrey, then you have a wedge of diamond/water in the face, and it is exiting at the 3 points, causing them to get polished first. (Gearloose had a discussion on this once, it is like a film boundary in a crank shaft for getting it oiled. You can develop huge pressrues this way) The pressure will never allow the sone to actually touch the lap, it kind of hydroplanes. But it is being ejected at the edges.


Some people run very dry laps. They put down the diamond, then wipe the surface doen, and run it dry. This allows the stone to get right down to the lap.

Even if yu run dry, the leading edge will polish first, because it see fresh compound. As you polish the leading edge, somw swarf starts to build up, and the center of the stone is seeing diamond as well as the swarf, so ti does not see as much diamond.


THIS IS ONE PERSONS UNTESTED GUESS>>>>>> It is plausible (at least to me) , but may not be true.

I think that that hit the other topics.

If your soft stop is not working, I really suggest you get it fixed. You are just beginning faceting, and it will be very tough to do quality work witht the machine working properly.

I havea few friends with facetrons, they ar egood machines, and one really nce feature is their ability to watch the dial bring in the face.

YOU STILL NEED TO INSPECT THE STONE ESPECIALLY THE LAST LITTLE NUDGE.

I agree that you can to some extent cut to ear, but that will only get you so far. I have a
ULTRATECH, that has a true hard stop, and even on it, you have to watch and adjust teh final meets by eye.

I have a digital display that reads to the xx. I was totally surprised how much flex was in the machine. I can get the display to change by .1 without any problem at all simply by pressing on the spindle. So you have to do the final adjustments by eye.

Do yourself a big favor, and get the machine repaired. You may be able to do some yourself, I am sure that there are posts on that. It will make your cutting much easier.


GOOD LUCK. I look forward to seeing your cuts in off the drop.


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