Scratching lap questions

[Miquel]

Hello

Is my first participation in this forum. I am from Spain and excuse me my poor English expression .

I am learning to cut with an old lapidary in the Barcelona area (in really is my uncle), and he use only the jamb peg old French technique. He learn in thirties with French Jura regions artisans.

I install in home an equipment, and I am cutting only glass (to learn more) , but I have some questions.

1.- ¿Why the 3.000 grid diamond faceting top plates (from Kingley North) are so abrasive?. Now I am cutting and prepolishing at same time with that 3000 grit, and is too abrasive yet. The professional Swiss synthesized diamond disc at my teacher home, is not as abrasive that that, (but he don’t remember its grid). I think will be better to cut with a disc more fine than my 3.000 lap, but doesn’t exist.

2.- I am polishing with Dynalap cerium lap. That disc polishing very well (specially the scratches surfaces from my 3.000 disc…), but that duration is not good. One sheet has a duration two or three stones (5 mm. more or less). ¿Is that the normal Dynalap duration …?

3.- I have observed than the Dynalap can inclusively cut very little faces, for example: the little stars in crown. That is better than use the 3.000 Dynanalap with the problems that I explain. I think that procedure reduces the Dynalap duration further….. ¿ Has any oneexperience cutting little faces directly with Dynalap?

4.- I use also the Darkside lap with Battstick cerium. The problem is the polishing is very, very slow, and I need to recharge the lap very often. I think the problem is I use too water, but if the lap dried the polishing is not good. ¿Do I any think wrong?.

Thanks
Miquel from Barcelona

[pegatha]

Welcome to the forum Miquel, I don't have the experience to answer your questions but some one will.   Peg

[Aussie Sapphire]

Hi Miquel,

I hope you will get a lot more advice on this from others as well but a few thoughts:

Although we sell #3000 plated laps because customers ask for them, we would recommend using good quality #3000 diamond on a metal lap as being a better method - much more long lasting and predictable results. Traditionally here, faceters would use #3000 on copper for pre-polishing but you can use a few different types - we suggest a BATT lap from Gearloose for this step.

Although Dynalaps (or similar thin film laps) do wear out quite quickly, I think they should last longer than you are experiencing?  Perhaps too much pressure on the lap?

Re the slow polishing on the Darkside, I think perhaps this might be more of a pre-polish issue.  If the stone is ready for polish and you are using a suitable polish/lap combination, then usually the polish should come up quite quickly.  If it is happening very slowly, perhaps an indication that maybe the pre-polish is not quite good enough.  There has been quite a few discussions on the Darkside which may offer some other things to try - more/less water, more/less pressure, for example.

cheers
Leah

[Orange Pirate]

I use also the Darkside lap with Battstick cerium. The problem is the polishing is very, very slow, and I need to recharge the lap very often. I think the problem is I use too water, but if the lap dried the polishing is not good. ¿Do I any think wrong?.

Hi

How old is your Darkside™?
The reason I ask is because I have used two from new and the same thing happen with both, real bad scratching that drove me nuts(Cerium Battstick™ on quartz).  Although the second time round I noticed the pattern repeating. It wasn't my pre polish. I was pretty much cutting with pre polish and anyway, once I had 'tamed' the beast I no longer pre polished anywhere near as much.
The amount of water didn't make a difference (reducing the scratching), the amount of polish neither. Lap speed, pressure changes all resulted in a horrendous gouge like scratching.

But what I did noticed was every time the scratching started there was black something being shed from the lap. Remove the lap and scrub it under the tap and go again. Instantly the polishing would improve until the black stuff appeared again, so scrub again. Each time a good polish run would go longer between scrubs. Once the black stuff stopped, magic happened.
I have no idea what the black stuff is or even if it's capable of making a scratch but I do know this ritual worked for me. Twice.

Once 'the beast' has been tamed it polishes at an impressive speed that will put a smile on your face with minimal polish and a damp lap (I use a plant sprayer/mister). It now loves quartz.

Although the Darkside™, tourmalike relationship did not work out so well. I had to pull the old warped Lucite lap literally from the bin for that one. The Darkside™ wanted to pluck the facets of my tourmalike to death. It wasn't pretty. But that's another story.

This is my Darkside™ story and I don't know if that will work for you but I definatly recommend persevering with it. You will love it.

HTH
OP

[Aussie Sapphire]

Remove the lap and scrub it under the tap and go again. Instantly the polishing would improve until the black stuff appeared again, so scrub again. Each time a good polish run would go longer between scrubs. Once the black stuff stopped, magic happened.

Good idea - a good wash is an easy thing to try and may just fix the problem.

cheers
Leah

[FlashGP]

You can also try the Darkside with 60000 grit diamond.  Bob Boddington told me to mix I tiny bit of  diamond on the pointy end of a tooth pick with 3 or 4 drops of diamond extender (sewing machine oil also works) and smeer it over the lap.  Then wipe it most of it off with the lap spinning.

It works for me.  I use good quality paper napkins (3 ply from Ikea) cut into 2 x 1 inch rectangles as wipes.  The one I wipe the diamond off the lap, I keep and add a couple of drops of snake oil or diamond extender to so I can periodically re-charge the lap.  I use a second wipe with snake oil or diamond extender to clean the ground stone off the darkside and at the same time re-oil the lap.  I do this every facet or two, hence the need to recharge the lap periodically.   There is just enough lubricant on the lap to make it look skiny, again the wipe removes most of the oil.

You might be able to try something similar with the cerium and water.

I expect the black stuff is ground stone from the polishing process.  If left on the lap it will ball up and scratch the facet you are polishing.  I have observed the same thing happens with too much polish on the lap if the lubricant dries out.

The manufacturer recommends using slow lap speeds with the Darkside.  I have a Facetron with the speed dial marked 0 to 7.  If I try to go above speed 2, the Darkside scratches.  This could be a result of heating of the facet through friction on the lap surface.  You could try slowing down your lap if it scratches.

Hope some of this helps.

[Orange Pirate]

I expect the black stuff is ground stone from the polishing process.

Possibly but it did only occur on both laps just when first using them. Once both laps had some use the black stuff disappeared and did not return.

Who knows. But worth it.

Cheers
OP

[Miquel]

Thank you very much for the answers .

I have worked hard and I have made some progress. At the moment I am cutting only glass and commercial strass (Swarowsky).

In first time, I am polishing now OK with Darkside, I have discovered that I need to put a little quantity of Cerium Battstick very often, in really, every face. But not too, only brush softly the lap. The Battstick of cerium consumption is not excessive, I think.

Now, I am discovering also that the Cerium Dynalaps do not last long, BUT… , I can put cerium from the Battstick on it, (like it was a Darkside or other synthetic lap). I think the plastic thin lap duration is not for ever…, but its duration it’s improved a lot.

Something else. ¿Is there somebody that experiment cutting little faces (for example little stars facet in crown) directly with polishing lap?. I recognize the real problem for cutting, with polishing lap, is to scratch the lap, but if you use a Dynalap, that problem it’s not important, (if you don’t broke the lap, of course, hihihihi). I think the lap duration is not good, but you can put some quantity of Cerium with the stick (as I wrote). The sensation of cutting a little and precise faces in that way is very good. The control is better than cutting with a bad cutting lap, at least, with my old and imprecise machine.

Thanks

Miquel

[FlashGP]

Something else. ¿Is there somebody that experiment cutting little faces (for example little stars facet in crown) directly with polishing lap?. I recognize the real problem for cutting, with polishing lap, is to scratch the lap, but if you use a Dynalap, that problem it’s not important, (if you don’t broke the lap, of course, hihihihi). I think the lap duration is not good, but you can put some quantity of Cerium with the stick (as I wrote). The sensation of cutting a little and precise faces in that way is very good. The control is better than cutting with a bad cutting lap, at least, with my old and imprecise machine.

60,000 diamond polish will cut slowly and I have done this by accident a couple of times.  I find it better to use slower speeds on the pre-polish lap and pre-polish in small facets then finish them with the polish.  I pre-polish with 8,000 on a zinc lap, which cuts like 3,000 diamond on copper. 

If you are using a copper, tin or type metal lap and 3,000 diamond as a pre-polish and you have a spare pre-polish lap, try 8,000 diamond as a pre-polish on the spare lap.  This would also slow down the cutting speed for the small facets. 

Alternatively sand the other side of your pre-polish lap and use 8,000 grit on this side and keep the 3,000 grit on the other side.  You would need to use a thin plastic sheet between the lap and the master lap to stop the 3,000 contaminating the 8,000 side when you turn the lap over for the small facets.

[Aussie Sapphire]

Now, I am discovering also that the Cerium Dynalaps do not last long, BUT… , I can put cerium from the Battstick on it, (like it was a Darkside or other synthetic lap)
Miquel

Yes - this is true.  For these thin film type laps, you can recharge them some to extend life.  I had not heard of people using BATTstiks to do this but there is no reason why it would not work similarly to adding more polish via a slurry.

cheers
Leah

[Ghost]

Polishing is actually grinding, but with a much finer form of grit.
It is perfectly ok therefore to cut in very small facets, especially in softish material, with the polishing lap, although if you are too ambitious, it may be a bit slow.   With very small stones, this can even be the preferable method.
In creating a new facet, you will usually start grinding at a sharp point or edge, so be very gentle with the first touches to the lap so as to avoid damaging or grooving the polishing lap.
Welcome to ALF Miguel.   Glad to have someone from Spain with us.
Regards,
Ghost

[REXL]

Miquel, glass is very soft and it also can have faults in it that show up when polishing, I use glass to test some designs .(I have a good supply due to an accident with a couple of candleholders). I suspect that your scratches are happening early in the cutting and only showing when polishing,
Glass is so soft I cut it with a 1200 grit and then put an Ultralap on top and polish. I only ever use a 3000 or higher when cutting sapphire.
If possible suggest you try and get some quartz to learn on, it has less problems than glass because it is harder than glass but softer than some others.
I bet your English is better than my Spanish.
REX