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Author Topic: Polishing laps  (Read 7458 times)

Spaghetti888

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Polishing laps
« on: October 23, 2016, 04:25:44 PM »
Hi all :) new here ???

I had a question about which polishing lap is best for stones harder than quartz. I'm currently using a copper lap/8000 diamond powder and tin lap/50000 diamond powder but started having issues with scratching....facets would polish then scratch, polish then scratch over and over. Have tried cleaning laps, using less powder etc, same result.

I wanted to try a different lap so a couple of questions regarding this!

1) If I were to purchase a batt lap, how do you prevent contamination from the 2 powders if you decide to use both sides?
Would you recommend using both sides, or just the one

2) Is a batt lap or darkside better for the final polish?


Thank you

Aussie Sapphire

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Re: Polishing laps
« Reply #1 on: October 23, 2016, 06:47:19 PM »
Hi all :) new here ???
1) If I were to purchase a batt lap, how do you prevent contamination from the 2 powders if you decide to use both sides?
Would you recommend using both sides, or just the one

2) Is a batt lap or darkside better for the final polish?


Thank you

1) - only with extreme care.  Some people use paper coffee filters to put under the lap to try and prevent contamination from the surrounds.  While it is possible to use both sides, the extreme care needed to keep both sides clean mean most people find it easier just to use one side only.  This is what we recommend - one side usage.

2) Laps are different - not necessarily one better than the other. A BATT lap is probably a more traditional way of doing it and used in same way as with any good quality tin alloy lap (there are a few out there).  Darkside is a versatile lap where you can mix and match diamond/oxide polishes but while they have generally been received very well with people finding them easy to use, there is the occasional user that has had more problems getting used to them.  As polish does not charge into the surface like a metal lap, you need to use much less and "touch" is a bit more of an issue.

Re scratching, hopefully others will have some good suggestions for you.  Have you changed direction of polishing - sometimes that can help if polishing troublesome material.

cheers
Leah

Aussie Sapphire - The Lapidary Warehouse

Spaghetti888

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Re: Polishing laps
« Reply #2 on: October 23, 2016, 08:01:00 PM »
Thanks so much for the reply.

I haven't tried changing the direction of polishing, actually I am not sure how to! I've been reading a bit about the darkside and batt however,  and am keen to try  ;D

Spaghetti888

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Re: Polishing laps
« Reply #3 on: October 23, 2016, 08:36:50 PM »
Oooh another question! Can I use the diasticks on the darkside? I am newish to all this

Bucket

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Re: Polishing laps
« Reply #4 on: October 23, 2016, 10:46:07 PM »
I use pewter laps made by a member of our club, but only a single side per grit to avoid contamination, except for oxides. What you are describing sounds like either contamination or possibly a build up of crud on the lap. This crud builds up as you polish and tends to make little balls and then scratch your facet. If that's what it is, you need to clean the lap and then try less diamond or oxide. Oxides generally need very little on the lap, I generally use cerium oxide in a very thin (like watered down milk) mix with water and even then only a couple of drops on the lap. A fine spray of water when the lap starts to dry keeps it moist.
Common sense isn't exactly common

Aussie Sapphire

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Re: Polishing laps
« Reply #5 on: October 24, 2016, 07:58:28 AM »
Oooh another question! Can I use the diasticks on the darkside? I am newish to all this

Yes - they were actually designed for them to help people not overdo the polish.  As it sits on the surface, if you use too much, it can ball up under the stone and cause scratching (like Bucket has mentioned in earlier message).  So the battstik and later diastiks were produced by Jon to help avoid this.

Bucket has some good advice re using very little polish.  If your faceting machine does not have a reverse direction, you can try polishing using an area of the lap on the other side of the centre spindle - ie. the other side where it is going in opposite direction on the stone.

Good luck.
Leah
Aussie Sapphire - The Lapidary Warehouse

Aussie Sapphire

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Re: Polishing laps
« Reply #6 on: October 24, 2016, 08:00:27 AM »
Also, you might have a look at this article which has listed out a whole bunch of different causes of scratching and some helpful hints on how to identify and resolve:


http://www.thegemdoctor.com/wp/2010/01/is-that-a-scratch/


cheers
Leah

Aussie Sapphire - The Lapidary Warehouse

Spaghetti888

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Re: Polishing laps
« Reply #7 on: October 24, 2016, 03:53:05 PM »
Great, thanks Bucket and Leah
 beers

FlashGP

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Re: Polishing laps
« Reply #8 on: November 16, 2016, 08:37:40 AM »
If you are using oxides you can mix 1/4 to 1/2 of a tsp plus a few frops of detergent in a spray bottle full of water and use this to keep the lap wet. 

I also then run a slow drip on my darkside to keep the polish and swarf from building up and forming balls to scratch the surface of the facet.

If using oil affiliated polishes like diamond, put 1 squirt on the Darkside tgen with a makeup cleaning wipe with 4 or 5 drops of Snakeoil on it wipe the lap clean.  As you polish, keep wiping the lap clean with this wipe.  It will keep adding minute amounts of polish, clean the lap and lubricate the facet.

Snake Oil is very thin and a lot friendlier than Automatic Transmission Fluid. 
 beers
Yours Sincerely
Flash (Gordon)

Spaghetti888

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Re: Polishing laps
« Reply #9 on: November 20, 2016, 09:42:31 PM »
Thanks for the advice

FlashGP

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Re: Polishing laps
« Reply #10 on: November 21, 2016, 08:44:44 AM »
You're welcome.  I hope it works for you.  I started off putting way too much 3k diamond on a copper lap.  My instructor didn't explain how the lap cut.  Consequently we just kept applying diamond instead of cleaning the lap.

Soft metal laps trap diamond on the surface of the lap and that diamond grinds the stone.  The colour that builds up is ground stone, swarf.  Once the lap is charged, a smalll application of coolant , usually an oli, should be all that is needed to cut or polish.

Hard laps like the ceramic and cast iron laps polish using oxides or diamond suspended in the lubricant between the lap and stone.  Metal laps with oxide probably worm this way as well.

In both systems you probably get a mix of the two methods but one will dominate.

The trick is working out how each works for you.

Happy faceting.
Yours Sincerely
Flash (Gordon)

Spaghetti888

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Re: Polishing laps
« Reply #11 on: November 24, 2016, 11:49:50 AM »
Omg, I've just come back to check the forum and for some reason only one line of my last post came through! I did write more than that  ???

I see, that explanation helps a lot!

I did previously try to ask what you thought of using baby oil vs snake oil as a lubricant? I've been taught with baby oil which works fine,  just wondering if you thought the snake oil was better?

 beers

FlashGP

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Re: Polishing laps
« Reply #12 on: November 25, 2016, 08:34:29 AM »
I started using baby oil.  But Snake Oil is a lot thinner and easier to clean off the facet to look for scratches.

Being thinner it takes less pressure to have the stone contact with the cutting surface of the lap.  This helps stop pressure related issues such as rounded facets and chipped edges.

It also cleans the lap and protects it with a thin film of oil.

As an example of how thin it is: When I started Bob Boddington suggested I put a drop of diamond extender on the lap and using a tooth pick pick up a tiny amount of diamond and mix it with the drop then smeer this on the lap and wipe it all off and facet.  The tissue used to wipe off the excess diamond is used to charge the lap from time to time during faceting. 

Baby oil is a bit thicker than diamon extender so the method works for both as with Singer Sewing Machine Oil.   But Snake Oil is so thin it spreads across the lap before you can add the diamond necessitating the use of several drops of Snake Oil.

From there I took Graham Kinsella's advice and bought a couple of bottles of isopropyl alcahol from Bunnings.  I poured the last half of my 8k diamond powder into half a bottle of isopropyl alcahol to make my own diamond spray.  Ditto for the 60k powder.  When my commercial sprays run out I'll do the same with those grits.

Both methods result in an invisible layer of diamond on the lap, which us the point of the exercise.  If you can see the diamond there is way too much on the lap.

...

I still use baby oil to look for inclusions in rough it is nearly as good as the refractive index fluid Aussie Sapphire sells.

Hope this helps.

Kind regards
Gordon.
Yours Sincerely
Flash (Gordon)

Spaghetti888

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Re: Polishing laps
« Reply #13 on: November 25, 2016, 08:13:28 PM »
Thank you so much!

Dugite

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Re: Polishing laps
« Reply #14 on: February 19, 2017, 07:02:00 PM »
When i got my first machine it come with second hand type metal laps they seemed to scratch everything, no matter how much i cleaned them.  They had been contaminated at some point with a couple of grains of coarse diamond grit which has been embedded into the surface and no amount cleaning would get it out. So the only solution is to re-machine the surface in a lathe (remove .5 mm) and start again. Which is what i did in my lathe. never looked back and never had a problem since.

 

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