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How to stop facetting stones.

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Author Topic: How to stop facetting stones.  (Read 496 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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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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mirkaba
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« Reply #15 on: March 26, 2016, 08:26:35 am »

I cannot imagine trying to use a hard steel disc or wheel for anything other than course grit sanding/shaping. ie 100 and 220 grit hard wheels on my old Crown. Not saying it can't be done. Just that I don't want to do it.  I have a 600 grit Crystalite wheel sitting on the shelf that I Removed from a Ring Leader a while back. If I ever get to it I will try to trade it off.
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Bob

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vitzitziltecpatl
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« Reply #16 on: March 26, 2016, 09:20:37 pm »

Yeah, there are people who can produce good cabs on hard laps, but the amount of time to learn those old-school skills must be huge. I chose early on to use the tools that let me cut opal faster and better.

Harder stones are easier, but I'll still do it the most time-efficient way. I don't think I'm lazy, but just figured if someone could show me in person how to cut perfectly smooth cabs on hard laps I'd try it. Until then, I'll keep using foam backers and flexible laps.
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« Reply #17 on: March 27, 2016, 09:58:02 am »

Hi All

Wow does that bring back some memories. In the late 70s when I was a young teen I started cabbing with a old flat lap and hard disks.I took some of my lawn mowing money and bought a subscription to rock and gem magazine. It did not take long to figure out if you are going to cab on a flat lap a rubber backing is a must. Mt dad cut me some disks out of wood and found some rubber and I started making my flat laps with wet dry sand paper.

I have a jenie for a while now and it is a monster for shaping i still go to the flat lap for finishing.

Thanks for the memories
Happy Easter
Bless
Shawn
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BluetangClan
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« Reply #18 on: March 28, 2016, 06:29:42 pm »

Some questions, where do you guys get your rubber plates from? I found a set on Ameritool-inc which is fairly costly but they do not have very high grit. Are the rubber pads re-usable when I get new. Wet dry sand paper an effective means of doing things? Would definately take down costs.

Like this? http://www.ameritool-inc.com/store/index.cfm/product/25_2/sponge-pad.cfm
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Hummingbirdstones
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« Reply #19 on: March 28, 2016, 07:18:09 pm »

Use the rubber pads under the resin diamond discs.  They have PSA on the back and you stick them on the plastic lap.  You stick the resin diamond discs on top of the rubber to make the sanding process more smooth.  I found the rubber pads at Kingsley North for less than Ameritool and there is a quantity discount.

http://www.kingsleynorth.com/skshop/product.php?id=46556&catID=187

Smoothing discs go from 220 to 3000 grit.  Don't know if you have an 8" or 6" machine, but here's the link for the 6" discs:


http://www.kingsleynorth.com/skshop/product.php?id=97048&catID=109

Eastwind makes high grit polishing discs, but note they are expensive (but really good):

http://www.kingsleynorth.com/skshop/product.php?id=46659&catID=182

You can use silicon carbide wet/dry sandpaper, but I've never used it.  Somebody else would have to tell you what to get in that department.
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Robin

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BluetangClan
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« Reply #20 on: March 28, 2016, 07:41:39 pm »

It doesnt say whether the pads are reusable or not? When it says pressure sensitive adhesive, does that imply it can be swapped out easily? I have an 8" machine.
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stonemon
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« Reply #21 on: March 28, 2016, 10:28:02 pm »

There is a re-usable adhesive that I used for polishing pads on my LU6X in the old days... seems like a number 537 or 357 or something... I will look for an old tube of the stuff.
I could change pads on the buffer and switch from say, tin oxide to rouge or cerium by just pulling off the one, and then press the other on...
To be continued.....
Bill
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vitzitziltecpatl
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« Reply #22 on: March 29, 2016, 08:24:43 am »

Feathering Adhesive is the stuff you can use to make your laps easier to swap out. It's commonly found anywhere you can buy automotive paint and body supplies.

For ease in swapping the Eastwinds I cut some scrap stainless sheet metal into 6" rounds and put a foam backer and lap on each one. They can then be swapped right out when used with an aluminum master lap.

The Eastwinds are costly, and any 8" option is a lot more than 6" ones, but if you can set up something like I did they will last a very long time.

Just use light pressure with the Eastwinds and be careful not to gouge them with a point or edge. They're tough as nails, not like the "film" types by others, but nothing will survive edges digging in very well.
 
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Hummingbirdstones
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« Reply #23 on: March 29, 2016, 08:32:21 am »

Feathering Disc Adhesive will allow you to change your discs.  http://www.kingsleynorth.com/skshop/product.php?id=87780&catID=594

The rubber pads are pretty permanent once you apply them to a disc.  I have never taken one off (never needed to yet), so just swapping out the actual cutting discs would work.  If you were going to use just one disc and keep changing the cutting discs, I would not peel off the paper on the PSA backing of the discs and just use the feathering adhesive on the backs.  I use the feathering adhesive for applying my leather polishing discs to a lap.

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Robin

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