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 Post subject: Trouble with cutting small stones
PostPosted: Wed Apr 19, 2017 10:11 am 
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I just finished my first cut yesterday. I wasn't able to polish because apparently my darkside lap is on backorder and will be arriving next week some time. I started with a marble since it doesn't matter if I can't polish something that cheap. After several mistakes and recuts, I finally managed to get a decent round brilliant out of it.

I'm now trying to cut a 4 carat piece of aquamarine. It's flawed, included, and a bit cloudy, so I don't mind burning 90% of it to mistakes. Unfortunately, the fact that it's so small is making it difficult. Cutting the pavilion, I can put in the breaks and girdle without too much trouble, but the mains are killing me. I'm using a 1200 grit lap and even then, barely a second with light pressure tends to overcut the facet and erase the breaks on that side. I decided to go up to a 3000 grit on a Batt lap, but while that seems to do a great job smoothing facets out and removing scratches, it's as if it has no cutting power to speak of. I'm using a 3000 grit universal base diastik to charge the lap. I was hoping that I could use that for cutting the aquamarine with a little less sensitivity, but it just doesn't seem to have the cutting power. Am I doing something wrong?


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 Post subject: Re: Trouble with cutting small stones
PostPosted: Wed Apr 19, 2017 10:19 am 
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For really small facets try turning the machine off and hand rubbing the facet in.

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 Post subject: Re: Trouble with cutting small stones
PostPosted: Wed Apr 19, 2017 12:53 pm 
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Quote:
it's as if it has no cutting power to speak of

Try charging it again - lots of times - as BATT loves to absorb diamond. In past I routinely used 3k DiaStik on BATT for final meets and prepolishing. I mostly cut tourmaline with the occasional garnet, beryl or other stones under MOHS 8. The BATT should look quite frosted when it's fully-charged - this could take a dozen stone's worth of charging or more if it's a new BATT.

I've since switched to his water-based PCD 14k sticks on BATT. I just applied it over the 3k area and this stuff rocks! Cuts as fast or faster than 3k, sets much easier and it's water-based. You can still charge it (using water) then switch to SnakeOil/oils if you don't want to use water.

For really small stones, I often polish in the final star facets or small facets. I use a GreenWing which has a Greenway center - this stuff will cut those very nicely but you have to lower the stone very slowly to avoid gouging.

Hope this helps

-Allan

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 Post subject: Re: Trouble with cutting small stones
PostPosted: Wed Apr 19, 2017 4:50 pm 
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Sounds like you are using a brand new 1200 lap, it needs to be broken in with a piece of synthetic sapphire or whatever you have, sapphire will be the fastest route. Once it's broken in, it will cut a lot slower.

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 Post subject: Re: Trouble with cutting small stones
PostPosted: Wed Apr 19, 2017 5:35 pm 
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You've got some good advice here, Corey. Bob Kay's advice about cutting on a stationary lap is a trick you'll find useful in a number of situations. Allan's comments on the BATT lap are dead on - if this is your second stone, it's very unlikely that the BATT is fully charged. Once it is fully charged, you'll be able to trade off cutting speed for finish. A fresh charge will cut more rapidly, then wipe it off for a fine prepolish.


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 Post subject: Re: Trouble with cutting small stones
PostPosted: Thu Apr 20, 2017 3:48 pm 
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If the facet is small or comes in quickly a prepolish lap like 3000K BATT works better than trying to cut it in on the 600 or 1200.


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 Post subject: Re: Trouble with cutting small stones
PostPosted: Fri Apr 21, 2017 2:17 pm 
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Regarding charging a BATT, Marsh discovered an easy method that works.

Spray the lap lightly with WD40 and wipe it off with a paper towel, preferably Bounty. Then charge as you are. When the lap seems to slow down a bit, wipe it with more paper towel. When the cutting is too slow, repeat the WD40 and wiping.

The wiping when the lap first slows is to remove the swarf from the cutting. The swarf seems to 'float' on the WD40 while the diamonds mostly stay there.

This also works equally well when polishing with diamond. I've used the method on Batt, Darkside and Matrix.

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 Post subject: Re: Trouble with cutting small stones
PostPosted: Sat Apr 22, 2017 7:00 pm 
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I recommend charging your lap initially as instructed by Gearloose. Jon has an instructional video posted on the Gearloose Batt lap web page. This process gives the batt lap a charge where one does not have cut a vast amount of stones to get the batt lap to its best potential. Every stone after will keep the lap even better charged wether your using diamond powder or the sticks
Greg

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 Post subject: Re: Trouble with cutting small stones
PostPosted: Wed Apr 26, 2017 11:54 am 
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Alright, I tried charging the lap more and it seems to have worked. It's still a bit slow in modifying facets that are off, but that actually makes it easier to avoid mistakes. I actually have the aquamarine's pavilion cut. Now I just need to wait for my darkside lap and transfer assembly to arrive so I can finish the damn thing. Once it's done, I'll post it.


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 Post subject: Re: Trouble with cutting small stones
PostPosted: Wed Jul 19, 2017 3:31 pm 
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Starting your cutting on small stones is the perfect way to learn, my mentor taught me this years ago. cutting large stones is a slow going process, smaller stones gives you the "feel" of cutting a (Type) of material. i will test cut small stones of the same material im planning to cut a large stone from.

If i also design or try a new pattern i use a small crappy piece of rough to test cut, what ever i can get on sale from a vender. $1. a ct rough.

If you remember anything on this forum, remember this ( pre-polish is everything).


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