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How to stop facetting stones.

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Author Topic: How to stop facetting stones.  (Read 472 times)
BluetangClan
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« on: March 22, 2016, 06:38:54 pm »

Using my flat lap, I am having a heck of a time trying to stop facetting my stones. So far the group I am on is on 1200 grit but I cant seem to stop it. :/
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light house jack
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« Reply #1 on: March 22, 2016, 06:59:49 pm »

When cutting cabochons using any kind of wheel the key is to never stop moving the stone.  A constant flowing motion from the time that your stone touches the wheel and NEVER stopping for even a second or two is the key. If you pause, you get facets on your stone. When you are ready to pull away from the wheel, pull quickly.
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BluetangClan
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« Reply #2 on: March 23, 2016, 05:43:24 am »

I have been. Thinking maybe I have my speed still set too high, right now its about half speed. I end up with ridges running the length of the stone, especially in the softer stones. Obviously not as big an issue with harder stones but still there.
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slabbercabber
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« Reply #3 on: March 23, 2016, 06:35:02 am »

A light touch will help.  Also the motion you use will have a great effect.  Experienced cabbers will use every motion imaginable, but for starting I would suggest rock and roll.  That is keep the motion circular while moving the general area of grinding around.l
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light house jack
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« Reply #4 on: March 23, 2016, 07:18:21 am »

Rock and roll is a good way to describe a good motion.  Think of not only your hands moving but also your shoulders. Another BIG mistake that many cab cutters do is have too long of a dop stick. I teach using very short sticks and to hold the stick very close to the stone. This not only gives you support of the stone but you can feel what is happening between the stone and the wheel.  Look at a long dop stick and compare it to a broom handle duck taped to the steering wheel of your car and you sitting in the back seat trying to drive down a hill controlling the car holding on to the tip of the long broom handle. You have little control. Short dop sticks folks.
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vitzitziltecpatl
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« Reply #5 on: March 23, 2016, 08:10:03 am »

Ah, rock-and-roll... . I'll never forget how difficult it was for me to grasp the mechanics of how to do this when I started cutting. The best books and diagrams and videos of various people cutting didn't really help. Didn't have a local mentor to show me things in person.

If anyone here has a link to a really good demonstration video I'm sure it would help many new cutters with this very common question.
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GregHiller
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« Reply #6 on: March 23, 2016, 08:53:18 am »

It's also important to make sure the later stages of sanding/polishing pads have some 'give' to them (a soft pad underneath, or an expandable rubber drum helps).  You need to be able to distribute the sanding/polishing action over a larger surface area of the stone. 
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55fossil
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« Reply #7 on: March 23, 2016, 04:10:08 pm »

   Time to let the elephant out of the room. Do you mean you are getting flat spots from your coarse grinding? I hope I am not the only one who is wondering if that is what you meant. 
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BluetangClan
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« Reply #8 on: March 23, 2016, 07:26:27 pm »

no I am up to 1200 grit. I keep getting higher hoping it will clear the small ridges that keep coming up. My highest is a 3000 grit metal plate too.
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slabbercabber
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« Reply #9 on: March 24, 2016, 05:50:38 am »

This isn't all rock and roll but at least it is in there.
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vitzitziltecpatl
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« Reply #10 on: March 24, 2016, 09:33:27 pm »

Good video. Cab domed in 15 minutes.

Bluetang - are you using an Inland? When you said you have up to 3000 grit, all in metal laps it reminded me of starting on an Inland.

Best thing you can do is get some 1/8" foam backers and flexible resin/diamond laps. Just like GregHiller said, the foam-backed flexible laps will conform to the dome. That will get rid of the ridges and facets you're getting by using a rigid metal lap.
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James D. Farrow
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« Reply #11 on: March 25, 2016, 04:20:35 am »

I have an Ameritool and have steel discs up to 3000, and the softer mesh discs up to 14000.

The steel discs are much more aggressive. Don't even need to apply that much pressure and
they (even at the higher grits) will leave ridges (flat spots) if, like others have said, you don't keep the
stones in motion. It's not easy and it takes practice. You may lose a bit of your fingernails
(like I did until I started using finger cots) from rubbing on the discs but eventually you get
the hang of it. I am still working on it.  chuckle

James
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James D. Farrow
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"No more trains will be sold once the magazine leaves the station"
vitzitziltecpatl
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« Reply #12 on: March 25, 2016, 08:04:26 am »

Good to know about the Ameritool, and the steel laps are more aggressive. According to what everyone is saying about facets and ridges, the keys are very light pressure and constant rapid movement. I was probably way too heavy-handed when I started.

There was a video about cutting opal by either Keith Rigby or Greg Pardy - would have to watch again to remember which - that showed an amazingly fast (to me) rotation of the dop stick. I never did get that fast, so I'm happy with foam backers and resin laps.
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tkcaz
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« Reply #13 on: March 25, 2016, 08:23:42 am »

It's nearly impossible to completely prevent facets on a metal-backed lap. A light touch, slow speeds and plenty of water can help, but the odds are still seriously against you.  I don't use them on my Ameritool for sanding or polishing unless l actually want a flat surface.  Like others have said here, a soft pad is by far your best bet.
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Tim

James D. Farrow
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« Reply #14 on: March 26, 2016, 05:47:04 am »

I find the steel discs work fine on Jasper and Aventurine for example but for softer rocks like
Sodalite or Serpentine, definitely the soft mesh ones.

James
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James D. Farrow
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