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Author Topic: Ebonite diamond lap review  (Read 3573 times)

RoughCreations

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Ebonite diamond lap review
« on: August 19, 2020, 07:19:09 PM »
This review follows on from a post by Giel:
http://aussielapidaryforum.com/forum/index.php?topic=6670.msg58504#msg58504

Part 1 : The Unboxing

I received two disks from Bert in the Netherlands today, postage took a month to Tasmania under the current pandemic conditions. I purchased a 20/28 (800 grit) and a 63/80 (200 grit) disk. The following are my first impressions of the disks. Note that I have no interest, financial or otherwise, with the manufacturer of these disks.

The disks were packaged very well, there's definitely no way that they could get damaged unless a steamroller ran over the package.



Upon picking them up and handling them, my first impression was that these disks are very well made. They are manufactured by a craftsman. My next thought was that there's certainly nothing rubbery here - The cutting surface is very hard, there is no noticeable "give" when pushing hard with a fingernail, there is no way I would have picked the disk surface to be made of a rubber compound.



Apparently they are made out of "ebonite", a rubber with 40 to 60% sulphur, which after vulcanisation becomes rock-hard.



Because the diamond is embedded in rubber, the particles sink/spring back in the rubber when cutting, that is reportedly why they leave a very fine finish for the grit size. There is about 100 carats of diamond powder in a coarse lap. (less in the finer grits)
These laps are apparently suitable for cutting all gem materials.




The "sintered diamond" ebonite layer is 3 mm thick, attached to a solid 15mm thick backing plate made of some sort of tough, reinforced phenol resin material. The 3mm layer of diamond impregnated cutting material is comparable thickness-wise with a typical sintered bronze lap. The longevity of the impregnated ebonite layer is unknown at this stage - only time will tell.



The disk width is 150mm, and the central hole sits snug on my Facetron. There is no way you would get any flex in these disks. If these disks cut even half as well as they feel in the hand, it will be a win.



Now, I must add that I have never been lucky enough to have used/owned a traditional sintered bronze disk before, I have wanted to, but they are near impossible to source in Australia, and prohibitively expensive from overseas. So my comparisons will be with diamond-impregnated epoxy topper discs, such as the Lightning Laps and also with the ubiquitous Chinese-made diamond plated steel topper disks.



I see these disks potentially filling the gap somewhere between thin, short-lived topper disks and long-lasting sintered bronze disks. Coming in at a fraction of the price of the bronze disks (assuming you can even get them), if these disks cut nicely and last even moderately well in comparison, then they will be very competitive.



I believe that these ebonite disks can also be re-surfaced by the user with a sheet of glass and some wet and dry paper, thereby extending their lifetime.

I cut mostly quartz, and given its brittle nature, I guess if these disks perform well with quartz, they should work with most materials.



Stay Tuned for Part 2: The Cutting Begins...

« Last Edit: August 21, 2020, 12:54:17 PM by roughcreations »
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MakkyBrown

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Re: Ebonite diamond lap review: Part 1
« Reply #1 on: August 19, 2020, 07:45:54 PM »
Interesting, what is the backer made out of ?
Looking forward to your comparison :)

Faceting Frank

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Re: Ebonite diamond lap review: Part 1
« Reply #2 on: August 19, 2020, 09:29:46 PM »
A very detailed description of them there.
Unusually thick, what's the reason for that?

RoughCreations

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Re: Ebonite diamond lap review: Part 1
« Reply #3 on: August 19, 2020, 10:09:34 PM »
Interesting, what is the backer made out of ?
Looking forward to your comparison :)
phenolic resins I believe.
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RoughCreations

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Re: Ebonite diamond lap review: Part 1
« Reply #4 on: August 19, 2020, 10:12:33 PM »
A very detailed description of them there.
Unusually thick, what's the reason for that?
I don't know. Maybe it had to be thick for sufficient stiffness plus some over-engineering? apparently the ebonite rubber compound doesn't adhere very well to aluminium so a different material was chosen.
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Giel

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Re: Ebonite diamond lap review: Part 1
« Reply #5 on: August 21, 2020, 04:54:26 AM »
Good to hear that your laps have arrived, I am looking forward hearing about your experiences with them!
They will need a little bit of breaking in, but not as much as a plated lap. I use slow speed 400-600 rpm (sometimes even slower)and a slow water drip enough to keep it wet. Use a light touch on the 800 grit, If you use more pressure on the 200 lap it will cut very fast.

It is as roughcreations says.
The ebonite has to be glued to a backer with a special glue. But that glue does not adhere well to metal.
The backer is made of "pertinax" it is a composite material made with phenolic resin  and sheets of fibres, it is pressed into a hard plate.
The pertinax bonds really well with that specific glue, that is why he uses it. The backer is thicker than usual to provide stiffness.
My friend told me that he could have glued the ebonite to a thin sheet of pertinax and then glue the pertinax to an aluminium backer.
But he said he could not really be bothered as it is working just fine as it is and he is not making them commercially anyway.
I have not experienced any bending or flexing of the lap myself.
You would think rubber equals a lap that is flexible, but apparently bowling balls are  made with ebonite,so you could say it is a sheet of bowling ball material with diamonds embedded in it.

I did sand a few of them flat, spend an afternoon marking the lap on the machine and walking back and forth to some wet sanding paper on glass. The laps are absolutely flat and true now, no flutter whatsoever on the dial indicator.

« Last Edit: August 21, 2020, 05:06:14 AM by Giel »

RoughCreations

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Ebonite diamond lap review
« Reply #6 on: August 21, 2020, 03:30:11 PM »
Part 2: First Impressions

I selected a nice big slug of smoky quartz to test with, about 20mm square. As mentioned before, I like to cut big smoky quartz. I’m cutting a Fusion 49 pavilion with a Classic Fusion crown from Andrew’s first book.



I bedded in my 200 grit lap by running a dopped quartz crystal slowly over a slow-turning quite wet lap (just past 1 on the Facetron speed dial).



I began by cutting a preform temporary centre point (96-24-48-72) at around 35 degrees by roughing in first with a 150 grit plated lap, then moving to a 180 grit plated lap.

I then cut with the 200 grit ebonite lap on 3 of the 4 pyramidal sides. The 200 grit ebonite disk quickly produced a very nice even matt surface, with no rogue scratches, and just as importantly, no observable chipping on the facet edges. I could run my fingernail smoothly down the two ebonite cut edges without it catching, nice. The finish was comparable to what I usually get with my slightly worn 600 grit plated disc.



I noticed a slight smell, reminiscent of the smell of my rear tyres after taking off too quickly in the wet (back when I first got my car licence).

I bedded in my new 800 ebonite disk as before, and went to work on the same 3 sides, working at slow speed with plenty of water. Don’t be fooled though, these little puppies bite. My protection is the fact that I am working with big facets, so cutting is usually a slow-motion affair for me.

In no time I had a fine finish on the 3 sides. No orange-peel, no pits, no rogue scratches. It's clearly ready to go straight to cerium oxide on my beloved Darkside lap. The finish with the 800 ebonite is comparable to what I normally get with my 1200 grit diamond-impregnated epoxy topper lap, but even more uniform.





The fourth side (using plated disks) was problematic. I will have to go back to 180 as there are some small pits that are not coming out with my 600 grit. The 150 pulled some chunks out that I thought I had fixed at the 180 stage. My normal process of cutting often results in me going back and forth between grits, and I have grudgingly accepted this, but I am now starting to realise that it doesn’t have to be this way.

Now, I’m always a bit suspicious of reviews that are all positive, and have nothing negative to say. Ummm, …. , ummm : OK, I know - the disks are a bit thick so the top surface is level with the top of my splash-guard, so things can get a bit damp if you run them fast. There.



These disks are curiously retro – the component materials belong to times gone by: phenolic resins, vulcanised rubbers (rubber bowling balls were introduced in 1905, but synthetic plastic balls dominated by the 1970’s). Pertinax paper for reinforcement - a “traditional material with a new future” according to the German manufacturer. That’s it: the materials all seem to come magically together to produce a traditional disk with a new future.

There are a lot of disks available out there, but most seem to be thin topper laps these days, consumables effectively. I recently started using 3mm thick Lightning Lap toppers (mentioned earlier) which I quite like. They are AUD $100 each, so not cheap, and the diamond impregnated resin layer is barely 0.5mm thick from what I can tell. The ebonite disk “business layer" is 6 times thicker, and it can be re-dressed by the user. Not much scope doing this with a thin topper lap..

Disk manufacturers are obviously capable of making affordable long-lasting, performance disks if they want to. If Bert can make these wonderful disks in his shed, why can’t we see some more commercial offerings like this?

I will continue to test the performance of these ebonite disks, but sometimes you just know when you are on to a good thing.
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Giel

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Re: Ebonite diamond lap review
« Reply #7 on: August 21, 2020, 05:29:04 PM »
Quote
I noticed a slight smell, reminiscent of the smell of my rear tyres after taking off too quickly in the wet

I thought it smelled similar to cutting onyx. Don't worry, those are vapors from the ebonite, because it is new.
That smell wont last and soon you wont smell it when cutting.
Imagine the smell when vulcanising these things!  :o

The cutting action will slow down a little bit after breaking in so it wont cut as agressive as it does now.

MakkyBrown

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Re: Ebonite diamond lap review
« Reply #8 on: August 22, 2020, 08:17:50 PM »
Finish looks pretty nice :) How fast does the 200 cut?

Faceting Frank

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Re: Ebonite diamond lap review
« Reply #9 on: August 22, 2020, 08:38:22 PM »
The finish you mention about not leaving rouge scratches is good. Because as you get to the finer grits, cutting them out can be a real pain.
I feel that its not going to produce sharp edges to the facets, but that wont be a problem if your going from them to say a 3000 grit BATT lap.

RoughCreations

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Re: Ebonite diamond lap review
« Reply #10 on: August 23, 2020, 01:00:34 PM »
Finish looks pretty nice :) How fast does the 200 cut?

With plated, I use 150 (for roughing-out sometimes) 180, 600 and 1200 for most of my cutting of large quartz. I would compare the ebonite 200 with a slightly-worn 180 plated disk purely in terms of speed of cutting.
RC
« Last Edit: August 23, 2020, 01:25:00 PM by roughcreations »
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RoughCreations

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Re: Ebonite diamond lap review
« Reply #11 on: August 23, 2020, 01:20:52 PM »
I feel that its not going to produce sharp edges to the facets, but that wont be a problem if your going from them to say a 3000 grit BATT lap.
Hi Frank, good question. I find it difficult to quantify the sharpness of my edges after an 800 ebonite finish. They seem sharp to me, bearing in mind that I haven't gone to my final polish on cerium oxide (Darkside lap) yet during my testing.
What physical property of a disk determines the sharpness of a facet edge? If it is purely a function of the effective hardness of a disk's substrate, then it is likely other formulations (metallic bronze etc) holding the diamonds may be superior in this regard. These ebonite disks are very dense, flat, and the substrate is quite hard - just like a bowling ball, as mentioned earlier.
RC
« Last Edit: August 23, 2020, 01:23:12 PM by roughcreations »
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xcvator

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Re: Ebonite diamond lap review
« Reply #12 on: August 23, 2020, 02:49:22 PM »
You might be able to get a spray hood made with a 3d printer. I had 1 made for my slant cabber, I put pics in the gallery but have no idea how to put it here   ::)








Images added by admin (using the Medium BBC code)
« Last Edit: August 24, 2020, 08:44:30 AM by Aussie Sapphire »

Faceting Frank

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Re: Ebonite diamond lap review
« Reply #13 on: August 23, 2020, 04:20:08 PM »
 Start your post by entering all the text. Go to your gallery and select the picture, below it is a box with codes in it. Select the third code down by dragging the curser along it so the entire code is highlighted. Press Ctrl C, click the back arrow at the top left of the screen till your back to your post. Click on the end of your text and press Ctrl V. The code will appear in your text, press post.

Dihusky

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Re: Ebonite diamond lap review
« Reply #14 on: August 26, 2020, 04:42:57 PM »
Very interesting Roughcreations, excellent review. Love to try one of these against my 1200 sintered, looking at the photos the off lap finish might be much better so allows one to skip direct to polish. Depending on the material I normally have to go to either 3k or 8k pre-polish.

It would be interesting to see if they get embedded with stone chips which can happen with sintered.

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