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 Post subject: Dops
PostPosted: Tue Jun 07, 2011 11:23 pm 
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After three years of struggling with my facette GM2 I've finally found the problem. The key inside the quill is not right. Ever since I started to not use the keys in either the transfer block or inserting them into the quill I've been money. This was also proved by Stonebender who cut an emerald shaped stone today with near perfect accuracy. Are keyless dops from different manufacturers compatible with other machines? I'm looking now for a complete set of keyless dops. I can say that the last two weeks of cutting have been my most enjoyable now that I figured this damn problem out.

Justin


Thanks Facette for not fixing that :|


Last edited by SinCity on Wed Jun 08, 2011 12:09 am, edited 1 time in total.

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 Post subject: Re: Dops
PostPosted: Tue Jun 07, 2011 11:54 pm 
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Welcome to "Club Old School" 8) When my old GMI died several years ago, I bought a GMII and was sent a pretty complete set of keyed dops with my purchase. I've NEVER cut a stone with keyed dops yet. They still sit shiny and unused in my tool bag.

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 Post subject: Re: Dops
PostPosted: Wed Jun 08, 2011 12:06 am 
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What dops do you use Jeff?


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 Post subject: Re: Dops
PostPosted: Wed Jun 08, 2011 12:28 am 
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I am a GMII owner, and while I absolutely love the machine, I have never had anything but disappointment when using the keying system.

I imagine the keying system is perfect for when you remove the dop fromthe quill midway through the stone, but when you cut tables at 0deg and cut 4 or 5 stones in a day, there is no need to take it out until it is finished.

Using the keying system for transfers was just an exercise in futility. I tried both the standard and deluxe fixtures, and the keys would never quite line up, and would generally be worse than I could get holding a facet onto the lap and tightening the collet.

Long story short, after spending 2 years battling with the system and only inserting the dop short of the key, I decided I needed to move to a keyless setup. I did a lot of investigating, and I decided the best way was to just cut the keys off the fac-ette dops.

I looked into other brand dops, but short of some custom manufactured pieces, couldn't find anything without a key.

Fac-ette dops are machined to .250" while some others are .249". Polymetric dops came the closest, but they have a long slender key down one side and I wasn't 100% certain it would not interfere.

I used a 45 degree adaptor, and a 220 crystallite lap, and over the course of a few hours ground the key off all 80 of my dops. It was worth the time I spent on it, and I now have a dop set built to fac-ette specs without the drama of the keys.


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 Post subject: Re: Dops
PostPosted: Wed Jun 08, 2011 4:04 am 
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All 80 dops?.... Wow. At that point i'd just drop them off at a machine shop or something. That's determination.

Justin, seems the problem should be no more. It sure was nice seeing you so excited today that a new world of gem cuts has opened up for you. Thanks again for having me over. I always enjoy it.

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 Post subject: Re: Dops
PostPosted: Wed Jun 08, 2011 9:02 am 
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I guess I don't understand this. What could the key possibly do to throw things off? I too have a GMII and do use the keys on the dops. I find that after a transfer, I normally end up rotating the cheater from 0 to 4 and away I go.
I'd think if I didn't use the key in the dop, I'd still end up using the cheater to line up the stone.
If I try to tighten up a dop without the using the key, the the dop will always rotate a bit while tightening the collet, so I find the keys very useful.

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 Post subject: Re: Dops
PostPosted: Wed Jun 08, 2011 12:13 pm 
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I guess I don't understand this. What could the key possibly do to throw things off? I too have a GMII and do use the keys on the dops. I find that after a transfer, I normally end up rotating the cheater from 0 to 4 and away I go.
I'd think if I didn't use the key in the dop, I'd still end up using the cheater to line up the stone.
If I try to tighten up a dop without the using the key, the the dop will always rotate a bit while tightening the collet, so I find the keys very useful.


I was just about to write these exact thoughts when I saw Precision's post.
The only way the key can mess anything up is if you actually remove the stone while still busy with the pavilion or crown and then expect to get back to the exact same spot on a facet.That does not work too well in in my experience but otherwise the key is just a reference point,nothing more and nothing less!

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 Post subject: Re: Dops
PostPosted: Wed Jun 08, 2011 1:15 pm 
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If the key system is not also zeroed, this seems like a very real problem. It would be the same if the cheater was not set to zero with a keyed system. The incorrect alignment would then dial the reverse changes in on the cheater after transfer. Also, if there were a burr or abnormality in the key in the quill, it could also cause similar issues with unreliable "repeatability".

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 Post subject: Re: Dops
PostPosted: Wed Jun 08, 2011 1:40 pm 
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My faceting machine is (in)famous for being "not very well built", I'd say (and I agree for the most part to this statement). I've keyed dops and I suspect the transfer fixture is badly aligned. There's a (little) error, but it's repeatable. So I start cutting with the cheater NOT set to zero. I set it to have it about at the zero position after the transfer. Anyway, after the transfer I always paint a girdle facet with a sharpie, set the quill at 90 deg, and cheat until I can get rid of the sharpie mark with a swipe on the polishing lap (I like to use the lightninglap or my useless corian lap for this: robust and light in color so I see better if the ink leaves the stone even without looking at the stone directly).
I find keyed dops are very good for a pre-alignment, and I appreciate that, but I never fully trust them for getting a "perfect" alignment.

All the "sharpie strategy" takes some time, but it actually saves a lot of time because I almost never have to catch the "spirals" with the cheater when cutting. When I didn't it, it was quite frustrating to cut a row just to discover I was misaligned, then I had to cheat a first time, just to discover I cheated too much, so back cutting the same tier again. Just to discover that there's no much girdle left... :D But those times are gone for good. Now I align with the sharpie and cut right away. 5 minutes very well spent, imho.

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 Post subject: Re: Dops
PostPosted: Wed Jun 08, 2011 7:15 pm 
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I often don't have my cheater zeroed when I start a stone. It really doesn't matter where it is since all it does is rotate the quill a bit, like splitting teeth on the gear. Everything is relative. Once I start cutting, I never move the cheater except after the transfer, and then only once to get things lined up. I use a very similar method to what Maialetto does. Once things are lined up again after the transfer there is no need to use the cheater again. Now I suppose if your machine was buggered up you may need to. Neither my Gem Master II or my Alpha Tourus have had the need to move the cheater once I start cutting.

I keyed dop, isn't what's causing any problems, it's not re-alinging the stone after the transfer. The un-keyed dop only forces you to do this.

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 Post subject: Re: Dops
PostPosted: Wed Jun 08, 2011 8:45 pm 
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Now I align with the sharpie and cut right away. 5 minutes very well spent, imho.


From what I have seen, keyed dops are a solution in search of a problem.


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 Post subject: Re: Dops
PostPosted: Wed Jun 08, 2011 9:15 pm 
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I can't really explain why it's causing the problem. I can say that out of 150+ stones I've cut on the machine I maybe had 3-4 stones that were cut using the keys that when transferred came out with good accuracy. As I mentioned in an earlier thread, after transfer, each crown facet in relation to the girdle facet began to drift around the 43 index, it made no difference in the dops, wax, epoxy etc. Now, I rotate the dops 180 degrees so the bottom of the dop key rests on top of the quill key. After transfer I do the same thing. I do have to rotate the cheater extensively after transfer but because all the facet alignments are equal (in relation to the girdle facet) its very quick to dial in. I'm 5-5 for well aligned stones after trying this method. As Gene pointed out, because it's not locked in, when I tighten it up it does rotate a bit so I tighten it while the stone is on the lap on the girdle facet. That helps it stay place. Can't explain it, just know that it works.

Justin


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 Post subject: Re: Dops
PostPosted: Wed Jun 08, 2011 9:59 pm 
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When you used the key on the dop, did you also after transfer use the cheater to line the stone up again? If so, you are doing absolutely nothing different now, other than not allowing the key in the dop to assist you in tightening the collet.

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 Post subject: Re: Dops
PostPosted: Wed Jun 08, 2011 11:43 pm 
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After transfer I would cut three facets at 3,9,15 then 45,51,57 (SRB example). I would then compare where those facets line up to the girdle. The issue is that the first set would meet at 1mm (example) to the right of the girdle facet, and the second set would meet 1mm to left of the girdle facet (it would be a gradual drift up if I cut them all). Now, without using the keys, the same example both the first set and the second set would meet at 1mm to the right of the girdle. Equal placement all the way around of 1mm to the right. Use the cheater and everything is good. The only thing that I can come up with is that something is not right with the quill key.


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 Post subject: Re: Dops
PostPosted: Thu Jun 09, 2011 12:09 am 
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I can only speak from my experience of using the key in the Fac-Ette.

Using the keys would result in a "spiral staircase" girdle that indicates a transfer misalignment rather than a "saw tooth" girdle that means you need to adjust the index splitter to align the crown.

My hypothesis was that the key was not 100% central in the quill, rather it is a few thousandths to one side, which when the collet is tightened leads to the stone being slightly off axis, even if the transfer is perfect.


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