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Author Topic: Resin-bonded scissor-grinding lap  (Read 353 times)

RoughCreations

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Resin-bonded scissor-grinding lap
« on: May 24, 2021, 05:33:21 PM »
For those of you, like myself, where too many disks are never enough, I present the Chinese-made resin-bonded scissor-grinding lap.

I was first alerted to these laps by MakkyBrown, he had bought one on AliExpress from "Brushless Motor Store", however they appear to be available generally on the net, too, such as https://www.moresuperhard.com/2/grinding-laps-for-gemstone.html. Makky can provide his opinions on this disk, too I am sure. The manufacturer also states these are suitable for gem material (see below).

I ordered an 80 grit version aimed at initial shaping of my large quartz pieces, and got it landed in Australia for just over AUD $100. I normally wouldn't go anywhere near that coarse a grit in electroplated disks for shaping quartz, due to the microfractures that can be created, but these disks are more like sintered disks in nature, and cut much more gently for the given grit size. In fact, an 80 grit electroplated topper disk would probably grind your nice piece of quartz into a pile of paving sand quick smart.











This little beastie is built like a tank and weighs a tonne - mine came in at 834g for 150mm diameter. They seem well-made and have a nice finish. They are a very thick lap, my 80# is 16.5mm, including 3.5mm of diamond-bearing layer on the 13mm alloy base plate.

It fits my Facetron nicely, with the disk surface at exactly the same height as the top of my splash-pan (will have to run slower to avoid too much mess).

The manufacturers guff reads:
Quote
Resin bond diamond grinding wheel, high grinding efficiency, low resistance, good wear resistance, not easy to wear, high grinding accuracy, can process all kinds of high hardness materials and metal materials 2. Resin combined with advanced technology, high-quality diamond production, uniform sand particles, not easy to drop sand, has extremely high hardness and is not easy to burn the workpiece, good concentricity, the wheel will not swing. 3. Grinding wheel with high concentration of 150%, longer service life, hard and durable. 4. Can process high hardness materials, metal materials, especially materials that are difficult to process with ordinary abrasives. Can be used for rough grinding, fine grinding and polishing. This grinding wheel is specially used for grinding hairdressing scissors, hair clippers, clothing scissors, jade, agate, sapphire, quartz, ceramics, etc.

My first experience with my new 80 disk went very well. I started cutting a large smoky citrine in a square Fusion 5x5 design, 22mm wide. The progress was smooth and fast, with no chipping of note - nice.



The disk is pretty flat and runs true, with no obvious peaks or troughs. The feel while cutting is gentler than I was expecting for such a coarse quoted grit size. The rate of material removal is what I was hoping for with big quartz facets such as I have with this stone.
Some of you may remember that I purchased some of Bert's vulcanised rubber disks from the Netherlands a while back, I still use these rubber laps as my primary disks (200# and 800#), and they are both going strong (see link to old post below). This 80 grit, whilst certainly smooth to cut with, isn't the silky smooth experience of Bert's fine disks, even allowing for the coarser particles in the coarser disk. It would be interesting to compare this with Bert's 80 down the track.

https://aussielapidaryforum.com/forum/index.php?topic=6707.msg58851#msg58851

RC
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FlashGP

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Re: Resin-bonded scissor-grinding lap
« Reply #1 on: May 24, 2021, 05:57:57 PM »
Thanks RC,

They look interesting and easier than making our own.

I have had a go at making a 600 grit resin bonded silicon carbide lap. As an experiment.  It works, but I need to dress it flat.  My work bench has a small slope in the step treads I used for it.  As a result the lap has a slight lean.  But otherwise it seems successful.  20 gems sc to 50 gems liquid glass.  Takes about 12 hours to set about 5 mm thick on a worn out topper lap.

Regards
Flash

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Flash (Gordon)

RoughCreations

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Re: Resin-bonded scissor-grinding lap
« Reply #2 on: May 24, 2021, 08:08:41 PM »
I have had a go at making a 600 grit resin bonded silicon carbide lap. As an experiment. 

I need to have a go at a DIY lap myself. I have the gear, I bought some 320 grit diamond powder a while back, have epoxy and some copper powder -just need to stop analysing it so much and just do it.
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MakkyBrown

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Re: Resin-bonded scissor-grinding lap
« Reply #3 on: May 24, 2021, 08:29:27 PM »
I have the 80,320,and 800. Still figuring them out. 800 is a great prepolish on softer materials but will start to give hints of orange peel on sapphire. Cuts a lot finer than my 800 sintered. 320 is probably a pretty good cutting lap and could probably got too 3k off it on most materials. They are quiet well behaved and produce a lot less deeper scratches than metal laps.
My 320 did have a scratchy/high spot but i think that has now disappeared.Not bad for about $100 each delivered.
MB

FlashGP

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Re: Resin-bonded scissor-grinding lap
« Reply #4 on: May 25, 2021, 08:53:11 PM »
RC, the Lightning laps don’t seem to use copper as a carrying medium.

Given diamond is carbon based I expect it will be happy enough bonding (hanging out) with the carbon atoms in the epoxy.

I used liquid glass because Bunnings no longer sell Wattyl 7008 epoxy floor sealer, which I expected would work well.
Yours Sincerely
Flash (Gordon)

RoughCreations

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Re: Resin-bonded scissor-grinding lap
« Reply #5 on: May 26, 2021, 10:09:35 PM »
RC, the Lightning laps don’t seem to use copper as a carrying medium.

Given diamond is carbon based I expect it will be happy enough bonding (hanging out) with the carbon atoms in the epoxy.

I used liquid glass because Bunnings no longer sell Wattyl 7008 epoxy floor sealer, which I expected would work well.

Very true, I have a Lightning Lap and it definitely has nothing resembling copper or other metal powder in it, looks like a fairly simple construction. I do like the idea of using stuff from the hardware store where possible. You have the right idea - starting it simple.
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