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Author Topic: please advise on lap choice  (Read 1416 times)

Dihusky

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Re: please advise on lap choice
« Reply #15 on: October 29, 2019, 07:49:27 PM »
Practice is what it's all about, BUT and it's a big BUT don't go too broad in your selection. Sometimes new Facetors end up trying so many options they never get good at any and end up in a state of total confusion.

Rough shaping a stone up to 600 or 1200 is easy, being conscious of the depth of damage different grits can cause. It's the pre-polish and polish that gets people into the most trouble and they try something different before discovering if it is the lap or their technique that's causing the grief.

I use 60k diamond on a tin lap exclusively for polishing, but sometimes I run fast, sometimes slow, some facets are even polished in reverse and others are simply wiped across the lap with me slowly rotating the lap by hand, I never change the lap, I regularly dress it for flatness and I use bugger all diamond on it. I just know it works 100% of the time because I have learnt all the different techniques to make it work. Yes I've tried others, Tin/Bismuth, Typemetal, Lucite, but always come back to my Crystalite Tin lap.

Keep it simple mate, 6 of the right laps should be all you need to cut virtually any material including synthetics.

Giel

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Re: please advise on lap choice
« Reply #16 on: October 31, 2019, 05:53:45 AM »
Thanx for the advice Dihusky.
I have some experience with faceting, I have cut some quartz in the past, polished it on a cerium oxide ultralap.
Cut and polished some tourmaline and garnets, with alu oxide on tin. I figured since I bought a new machine it's time for something other than an ultralap. (did not like those)

I have saved some of my good 6 inch laps from when I sold the old machine. I have three good nubonds left (350, 600 and 1200) that I will keep using for quartz. I want to buy an oxide polishing lap for quartz, darkside or greenway / creamway.

I can use the tin as is with alu oxide, or "convert" it into a diamond polishing lap.
Probably will buy a Batt or zinc for prepolishing with 3k or 8k.

Quote
I never change the lap, I regularly dress it for flatness and I use bugger all diamond on it.

How do you dress it for flatness?

What do you mean with bugger all diamond? Whatever is available, cheap ebay diamond powder?

anyways, thanx for the heads up!

FlashGP

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Re: please advise on lap choice
« Reply #17 on: October 31, 2019, 08:33:56 AM »
Hi Giel,

Bugger all diamond means you put a tiny amount of diamond on the lap and then wipe it off before you polish.  When I first started faceting Bob Boddington advised me to use a tooth pick to take a small amount of polish and put it on the lap.  Then to add 4 drops of diamond extender to the diamond and smear the slurry over the lap with my finger.  Then to wipe it off before I started faceting.

I now mix my own diamond spray, 2cts diamond, about 3/4 fiamond spray bottle of isopropyl alcahol and 10 squirts of Orange Power bench spray, any thin spray and wipr detergent will work.  This is to make the diamond disburse in the alcahol better and stop it clumping.

I then put several drops of extender on a face wipe used for makeup removal and 1 or 2 sprays on the facewipe.  This is then used to clean the lap as I facet.

I have a creamway and a darkside lap.  The darkside is more versitile and will take oxides or diamond.  It is particularly good for oxides.  I use Batt Sticks to draw a light line of oxide near the centre of the lap then slowly drip water on the line.  The small amount that washes over the lap is sufficient.

Zinc, copper, typemetal and bearing metal (pewter) all trap diamond in the surface of the lap.  I spray 4 evenly spaced squirts of diamond mix on the lap and using a roller bearing fron skate board wheels on a handle, roll the diamond into the lap surface changing direction once I have gone from side to side.  Then wipe the excess diamond off the lap.  I do this on the table before faceting to support the lap and avoid diamond spray contaminating my machine.

Use a different bearing for each grade of diamond.

You will need to recharge occasionally depending on the hardness and number of stones you cut.

I often just add extender to a facewipe and rely on the impregnated diamond to do the cutting.  I can even flush a charged lap with water when cutting quartz.

Regards
Flash
Yours Sincerely
Flash (Gordon)

Faceting Frank

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Re: please advise on lap choice
« Reply #18 on: October 31, 2019, 01:12:54 PM »

Faceting Frank

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Re: please advise on lap choice
« Reply #19 on: October 31, 2019, 01:15:27 PM »
I can’t remember where I came across this method of polishing with diamond, but it works and works well. I no longer use any other method for polishing stones with diamond. There is a lot of diamond on the lap, which is the opposite to what you would want if using the lap in the normal manner. I use 3k for pre polish in the normal manner on a Batt lap and 60k for polishing.

I move my polishing lap by hand. Just moving it back and forth while wiping the stone across the lap as you normally would. Just using the area shown with the arrows, the circular area is where the extra diamond mixed with baby oil is. The cutting area is almost dry, which is very important. The grooves in the lap will be full of diamond. But because you are wiping the stone from side to side, you are not running down the length of the grooves. Causing diamond to ball up and scratch.
I occasionally wipe the stone in the circular area to add more baby oil/diamond mix to the cutting area. This method will produce a perfectly flat facet and is surprisingly quick.

Frank.

Prooz

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Re: please advise on lap choice
« Reply #20 on: October 31, 2019, 02:11:58 PM »
All these different methods! that's interesting Frank. I have taken Dihusky's tip and running water on the copper lap for pre polish and it works well, the lap is staying cleaner, and polishing is quick on the tin. I have also cut my speed down on both laps, working great.

Cheers

Dihusky

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Re: please advise on lap choice
« Reply #21 on: October 31, 2019, 05:20:08 PM »
Geil, dressing the lap is a simple process but can take time. The process is rubbing the lap on wet & dry paper, same paper that is used for paintwork prep on cars.

What you do is get a piece of thick glass, 10mm is ideal as it's flat and wont distort, needs to be around 350mm square, a bit bigger than the paper.

Make up a centre peg for the lap, I have a timber drawer knob with a 1/2" peg in the centre.

Add a drop of soap to the wet & dry and a small amount of water, then start working the lap over the paper, you'll quickly see if it has high spots. Depending on the lap, you may use 120, 180, 240 grit to start with, then work down to 400 and 600 to finish.

The idea is to take the lap until it is fresh metal everywhere, then you know it's flat. Yes, it takes time and some elbow grease on an old lap, but once done you can take a stone from pre-polish to final without any cheating, and the polish goes in fast.

I rarely do this on my tin lap as it gets very little wear because coming off a trued copper pre-polish, both laps are accurate and flat.

Faceting Frank

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Re: please advise on lap choice
« Reply #22 on: October 31, 2019, 05:57:06 PM »
Just to give you all an idea on how effective polishing with a stationary lap is.
When I first started entering the AFG and US annual comps a few years back, I realised just how important a perfect polish was. Anything in the way of grooves or scratches that can be seen through a 10x loupe will lose points and that’s on every facet the judges find.
Also it’s very frustrating to come to the end of a difficult to cut stone and start to have problems with the polish. I’m not talking about scratches you can’t see with a 3x Optivisor, but ones that can be spotted with a 10x loupe.
So polishing all 4 entries in this years Oz comp with a stationary lap I scored 39.98/40. I wouldn’t have come close to that before, also its faster and makes it easier to tidy up minor meet point errors.

FlashGP

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Re: please advise on lap choice
« Reply #23 on: October 31, 2019, 07:34:49 PM »
Thanks Frank,

I'll give it a go on the next stone I polish.  I am about ready to convert my BAT lap into a prepolish lap because it keeps glazing up and throwing small specs of lap surface while polishing with 100k diamond.

I'm blaming subsurface damage from the initial cut nrrded to temove diamond when I had it machined.
Yours Sincerely
Flash (Gordon)

scratchie

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Re: please advise on lap choice
« Reply #24 on: November 01, 2019, 02:02:11 PM »
Flash,
I've always used a Battlap with 3000 diamond as a prepolish. Wipe any slurry off it frequently and always keep it with the slightest amount of oil on it. Your cosmetic cleaning pad will be ideal.
I find using a few specks of diamond powder better than other diamond preparations.
John

scratchie

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Re: please advise on lap choice
« Reply #25 on: November 01, 2019, 02:08:04 PM »
Frank ,
I have often had a problem with fine scratchies  on harder stones
when polishing - didn't seem to matter which lap I used .
Will certainly try your stationery lap method.
John

Giel

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Re: please advise on lap choice
« Reply #26 on: November 01, 2019, 06:28:17 PM »
Ah, bugger all means something like "almost nothing" in this case.  :)

Thanx everyone for the suggestions and advice, I will probably come back to read up on this thread when trying out the new polishing laps.
So use very little diamond, wipe of excess diamond, use very slow speeds on the lap, or no speed at all.
I will try out the mentioned methods on a few stones!






MakkyBrown

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Re: please advise on lap choice
« Reply #27 on: November 02, 2019, 07:16:35 PM »
Frank ,
I have often had a problem with fine scratchies  on harder stones
when polishing - didn't seem to matter which lap I used .
Will certainly try your stationery lap method.
John
Maybe it could be fine subsurface damage releasing particles on to your lap.


roughcreations

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Re: please advise on lap choice
« Reply #28 on: November 07, 2019, 10:20:18 AM »
I can’t remember where I came across this method of polishing with diamond, but it works and works well. I no longer use any other method for polishing stones with diamond. There is a lot of diamond on the lap, which is the opposite to what you would want if using the lap in the normal manner. I use 3k for pre polish in the normal manner on a Batt lap and 60k for polishing.

I move my polishing lap by hand. Just moving it back and forth while wiping the stone across the lap as you normally would. Just using the area shown with the arrows, the circular area is where the extra diamond mixed with baby oil is. The cutting area is almost dry, which is very important. The grooves in the lap will be full of diamond. But because you are wiping the stone from side to side, you are not running down the length of the grooves. Causing diamond to ball up and scratch.
I occasionally wipe the stone in the circular area to add more baby oil/diamond mix to the cutting area. This method will produce a perfectly flat facet and is surprisingly quick.
.
.
.
.
Frank.

Thanks Frank,
I have just tried your method on a recalcitrant mega-topaz I was having trouble with performing the final polish - worked a treat!
I should have bought a machine without a motor and saved some money, lol.

You can also see my 'poor man's diamond extender' in the background. Very good for cleaning the machine too.
RC
« Last Edit: November 08, 2019, 01:39:35 PM by roughcreations »

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