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Author Topic: Resin-bonded scissor-grinding lap  (Read 8548 times)

RoughCreations

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Re: Resin-bonded scissor-grinding lap
« Reply #15 on: May 05, 2024, 04:52:12 PM »
I saw a video about someone that was making his own rubber lab with silicon carbide grit and flex seal liquid clear, seem very economical and could be used for the 80/180 grinding. cannot source flex seal liquid in my country tho : https://www.youtube.com/watch?v=NPOmJwgH6TQ

That's a coincidence, I watched that same video a week ago!
That Flex Seal rubber is actually not bad stuff, if you can get past the bad TV commercials, lol. It is composed of styrene butadiene copolymer, which is basically car tyre material.
Looks like we can get cans of Flex Seal paste (rather than the liquid) here in Australia, a bit thicker than the gunk in the video, but should also work in a lap I reckon.

Quote
I've prepared a piece to measure grinding speed and will take macro shot of the result of each steps to compare once I get all of them. but metal being softer maybe the red/brown ones are not suited for gemstones

Looking forward to your results,

RC
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TheRockThief

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Re: Resin-bonded scissor-grinding lap
« Reply #16 on: June 02, 2024, 10:30:16 AM »
So I tried all of them.

The green ones are flat, well balanced and cut well.

the red ones are wobbly, reading the digital dial is impossible because of that, also they were all contaminated, there is several spot that do "tik tik tik" and make deep scratches on the stones.

As for surface finish, they are finer than regular disc.

the 80 green resin lap makes a finish between a 180-320 grit electroplated lap
the 320 green resin lap makes a finish equivalent to my 600 grit on a copper lap.
the 600 green resin lap makes a finish between 1200-3000

They cut as fast as their equivalent electroplated lap, which surprised me, and they are a lot quieter (I can't use the 320/80 electroplated lap at night since I live in an appartment)

I wonder how they will wear over time, will they become uneven with deeper spots? time will tell. if they do last a long time it will be very economical.
a 80 topper is almost destroyed each time I make a D20 dice, those topper cost 20$

I've prepared blank and I will do a video with macro shots comparing the finish on those lap and "normal" laps

Haven't faceted a whole thing with them yet.
« Last Edit: June 02, 2024, 10:32:31 AM by TheRockThief »

MakkyBrown

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Re: Resin-bonded scissor-grinding lap
« Reply #17 on: June 02, 2024, 09:21:12 PM »
The red wobbly ones I'd lap the cutting side flat using 220# silicone carbide on a sheet of glass. Figure of 8 actions for a bit then rotate 90 degrees, repeat . Then put it on the lathe and machine the back flat.

I have an 800 and it orange peels on sapphire so your 600 might do the same.
MB


Alaskan

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Re: Resin-bonded scissor-grinding lap
« Reply #18 on: June 02, 2024, 09:56:21 PM »
On multi-use laps my easiest to use and reuse are the basic 8" Corian from Annie at sales@sierragems.net using a hard wax on the surface while rotating and a thin slurry of Diamond powder from 600 to 50,000. Not a pro like you guys but seeing clean facets. I use one lap to cut the last meets with 3000 then wash the Corian lap with alcohol and go to 8000 for the meet then another lap for 14 K and another to 50 K. I tried my copper lap as another test then quit... scratches - will scrape the surface with a razor blade while turning slowly then dedicate the copper to 600. I recommend the 8" Corian... I think you will be pleased with them. Cheers.

PS: I have 5 of these laps for fine grit and use musical instrument oil for the slurry- the Corian laps do come in 6".
« Last Edit: June 02, 2024, 10:19:41 PM by Alaskan »

RoughCreations

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Re: Resin-bonded scissor-grinding lap
« Reply #19 on: June 03, 2024, 12:10:24 PM »
So I tried all of them.
Thanks for reporting back to the Forum

Quote
The green ones are flat, well balanced and cut well.
Excellent news.
Quote
the red ones are wobbly, reading the digital dial is impossible because of that, also they were all contaminated, there is several spot that do "tik tik tik" and make deep scratches on the stones.

As per what MB said - lap them, then turn them on a lathe if required. For your 80 grit red one, I wouldn't worry if the dial indicator whips around, just ignore it - you would be almost pre-forming at that coarseness anyhow.
Quote
As for surface finish, they are finer than regular disc.
the 80 green resin lap makes a finish between a 180-320 grit electroplated lap
the 320 green resin lap makes a finish equivalent to my 600 grit on a copper lap.
the 600 green resin lap makes a finish between 1200-3000

They cut as fast as their equivalent electroplated lap, which surprised me, and they are a lot quieter (I can't use the 320/80 electroplated lap at night since I live in an appartment)

I wonder how they will wear over time, will they become uneven with deeper spots? time will tell. if they do last a long time it will be very economical.
a 80 topper is almost destroyed each time I make a D20 dice, those topper cost 20$
I would expect them to cut a little slower with use, that has been my experience with my resin. When you want some extra pace, expose some new diamonds as per previous posts.

Quote
I've prepared blank and I will do a video with macro shots comparing the finish on those lap and "normal" laps
Sounds good, look forward to some pictures.

RC
« Last Edit: June 03, 2024, 12:30:48 PM by RoughCreations »
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RoughCreations

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Re: Resin-bonded scissor-grinding lap
« Reply #20 on: June 03, 2024, 12:26:24 PM »
On multi-use laps my easiest to use and reuse are the basic 8" Corian from Annie at sales@sierragems.net using a hard wax on the surface while rotating and a thin slurry of Diamond powder from 600 to 50,000. Not a pro like you guys but seeing clean facets. I use one lap to cut the last meets with 3000 then wash the Corian lap with alcohol and go to 8000 for the meet then another lap for 14 K and another to 50 K. I tried my copper lap as another test then quit... scratches - will scrape the surface with a razor blade while turning slowly then dedicate the copper to 600. I recommend the 8" Corian... I think you will be pleased with them. Cheers.

PS: I have 5 of these laps for fine grit and use musical instrument oil for the slurry- the Corian laps do come in 6".
Sounds like you have got a good system going, stick to it if it's working!
Will have to chase down a Corian lap at some stage, and add it to my arsenal of laps, lol.
I have been cutting a very recalcitrant Tasmanian topaz, and am also cutting some disobedient Tanga rhodolite garnets at the moment. I am winning the battle with the garnets, they like to chip at the facet edges, dragging the chip across the facet, and ploughing a big groove. ???
As to the topaz, I lost the battle I am sad to say. I tried everything: pulled out old laps from the bottoms of my drawers, changed direction, speed, polishing medium, lubricant, pressure, - you name it. There was something about the topaz, certain facets (probably aligning with the cleavage) would not polish, in fact polishing would create a worse surface the longer I persisted. I wasted too much time and just left some scratches on some of the large 30 degree facets. Luckily this stone was just another 'cube illusion' test cut, so no biggie. It's strange, as I have cut a lot of topaz, not so much Tasmanian though, and it is usually very well behaved.

RC
« Last Edit: June 03, 2024, 12:33:48 PM by RoughCreations »
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Alaskan

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Re: Resin-bonded scissor-grinding
« Reply #21 on: June 03, 2024, 10:11:57 PM »
Rough Creations on laps and problems with material that won't stop scratching or molecular disintegration - a plague without solutions - books on polishing by names of known, polish the brain more than the intended material but one theory that seems best is damaged layers below the surface caused by too coarse a grit when preforming or sawing. (Of course you know all this)
I have a couple well-worn 220 and 240 steel for coarse cutting the ears off of sawn square chunks but beyond that it seems to pay to form on as small a grit as I can and raise the rpm to compensate for the extra time it takes to get the preform.
Sorry for being verbose.  I learned somewhere of using CDs or DVDs as laps when a really crappy day of scratches and disintegration is in the works - a slurry of Diamond on a CD Disc can work magic but then it could be just slapping the TV clears up the image. I wanted some clarification on how you guys use 'lap speed' as I find myself cutting slower than probably is necessary and then speed up to 70% on the rheostat. I logged an image of my set-up in the file - becoming Diogenes' barrel with three dogs keeping me company. Cheers - fun communicating with you guys down under.

PS: trombone musical instrument oil works best for me - olive oil - mineral oil - too thick -  WD40 seems too thin.
« Last Edit: June 03, 2024, 10:34:25 PM by Alaskan »

RoughCreations

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Re: Resin-bonded scissor-grinding lap
« Reply #22 on: June 05, 2024, 10:47:42 AM »
(Alaskan's setup - Patriot 8 Faceting Machine)
« Last Edit: June 05, 2024, 01:03:58 PM by RoughCreations »
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Alaskan

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Re: Resin-bonded scissor-grinding lap
« Reply #23 on: June 06, 2024, 06:49:28 AM »
Polishing P5 & P6 on Vol #1 pge 30 of MB's Supernova design and having to change the mast setting to reach the zircon - earlier my incorrect impression was some part of the material was softer because it seemed to cut faster but now seeing the need to manually raise and lower the mast height to contact/cut the material is directly connected to the dop... index number. The dop appears to be bent in milliseconds of angle. Almost finished - transferring tomorrow which should prove or disprove this. Meanwhile 'chasing meets.' Maybe I should take up woodwork?

MakkyBrown

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Re: Resin-bonded scissor-grinding lap
« Reply #24 on: June 06, 2024, 12:10:28 PM »
There will always be error Alaskan, it's just a matter of how hard you look. A lot of my dops are slightly bent, I have hand piece run out, platen run out, lap run out etc etc. And index wheels are sometimes not cut accurately(not uncommon as they are only as accurate as the machine that cut them). If you are not planning to become a competition cutter find a middle ground where the stones will look next to perfect by eye but not take you weeks to cut.With most designs if you round to the 0.1 of a degree they should still perform well and perhaps make it easy for you to cut them. With your digital display, cut to the point of change to a new angle. The encoder on your machine uses a code wheel with lots of little lines on it. The point of change to a new angle is far more accurate than a 1/10 of a degree. Do this for the girdle and first tier then use meets. Cut a few stones and don't worry if your meets are a bit off, your stones will still looks beautiful, and you will get some reward for all your efforts. Increased accuracy will come with time.
Cheers
MB

MakkyBrown

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Re: Resin-bonded scissor-grinding lap
« Reply #25 on: June 06, 2024, 12:13:37 PM »
Alsakan, there will be no issues if you round the supernova crown angle to 1/10 degrees.
MB
« Last Edit: June 06, 2024, 12:18:16 PM by MakkyBrown »

Alaskan

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Re: Resin-bonded scissor-grinding lap
« Reply #26 on: June 06, 2024, 09:31:21 PM »
Thanks for the direction MB, the number of tenths on my dial indicator versus the digital display tripping to the next tenth appear as 10 to ~12 on different positions of the index wheel and then lowering further to touch on a bent dop was not noticed until later. Your explanation and other's experiences here is much appreciated and valued. There is something magic with turning raw material into glass with rainbows.
« Last Edit: June 07, 2024, 09:11:15 AM by Alaskan »

 

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