What type of grinding wheels can I use on my flexible shift to grind agate?

Hello everyone!

Thanks to everyone here, I now have a working water drip system in my grinding cabinet. Thanks!!

I have 2 questions!

My first question is what type of grinding wheel or discs(with mandrel) can I use with my flexible shaft to grind agate?

Also are there cushion rubber wheels that have coarse enough grit to cut stones with the hardness of 7 and still not creat a shock to the stone a person is cutting. I am thinking about the stone called Larimar.

Thanks as always, everyone’s suggestions and ideas are always appreciated.


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You should probably go look at a lapidary supply catalog. I would suggest Kingsley North to start. Follow what manufacturer specific products they offer to their manufacturer’s websites for more information. I can’t imagine trying to grind, sand and polish lapidary material with a flexshaft…Rob

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Diamond tools would work, but they need water to cool and lubricate. This could be a problem with a flex shaft. I have worked with Diamond tools in a small bowl of water, but only at slow speed and throughly cleaning the flex shaft afterwards. Still not the best practice.

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I took a look at the Kingsley North website. There are a few lapidary tools that can be flex shaft mounted. Following is a link to a Foredom stone carving kit that appears to be able to work a stone once it is rough shaped. Initial sawing and grinding will be the problem on a flex shaft. There are flex shaft mounted diamond tools, but as already pointed out by rone, you will need water to use them. Equipping a small lapidary bench can be done fairly inexpensively. Take a look at the KN website and those of the manufacturers that they represent for ideas. I started with a single arbor and tools that could be mounted on it. It has now grown to take up a quarter of my shop. Good luck…Rob


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I like the nova points for stones. I’ve heard of using vaseline or mineral oil rather than water to lube them, but I’ve never tried that. I use a water drip I rigged up and do initial grinding on another machine.

Ben Brauchler

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The standard lapidary diamond wheels that have a 3/32 or 1/8 mandrel work very well. You can easily use any 100 to 400 grit wheel, most of the 600 grit plated wheels will not work well. There is not enough plating on that size grit to stand up the runout of most flex shafts, most micro motors will work with that fine a grit though. The nova points work very well for sanding the grinding burr scratches they and the the grinding wheels need to water to lubricate them.

An easy water setup is to use a small dish of water and a kitchen sponge. Put the sponge in the dish and fill the dish with water just below the top of the sponge. When the stone gets dry, wipe it on the sponge. You will be doing about as much wiping as grinding but it is easy and fast.

The rubber wheels that are use to smooth silver and gold work very well to further smooth the stone. These wheels are available in several shapes, with, and without mandrels. They are available in soft and hard rubber. Some people like one, some like the other, both work. They can be used dry but I would ware a mask using any wheel dry on stone.

Depending on how fine a finish you want, diamond compound on hard felt will give you as good a polish as you are willing to work for. There are several different diamond polishing products available for stone, it is mostly personal preference.

There are several books available on gem stone carving, you might want to read several of them for more ideas.


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Get a p100 respirator and cut wet and in a well ventilated area that can be cleaned easily or there is a 100% chance you will develop lung problems very quickly! It only takes one day of exposure to cause permanent lung damage. I’ve seen someone develop severe asthma after a single weekend of exposure to rock grinding. People lie and say it takes decades, that complete nonsense. This hobby is 1000x worse than smoking and many people I talk to not only caugh like smokers but develop lung cancer. Even with water, there is shit all suspended in the air when you work, especially with a flex shaft. You just don’t see it unless the sun shins at the right angle. So many in my club and on the forums develop it, its not a coincidence even though they mostly deny it. For small things, use diamond plated burs in your flex shaft and then the nova points to finish it off. With that said, unless you want to get into this seriously, it is very expensive to do it completely safely but 99% of people don’t do it safely and ignore the long term damage they do. Cabs are cheap, can just buy them pre-made.


Hi everyone!
I want to thank everyone for all the great ideas and suggestions. I totally agree with the respirator. I have built a hooded cutting box with a water feed to the inside, so I am completely cutting with water. I use to use the sponge method, however have now built my own box to cut in.
My work is with specialty stones that are no larger than the size of a 50 cent piece however mostly are quarter in size and down. So that is why I am using a flex shift, plus it does not take up a lot of space.

Thanks again for everyone’s help.


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How do you hold the stone when you are working on it?

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If is small it can be put on a clay or wax mound in a glass bowl or if a little larger , hand held.

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I am often cutting small 4 - 8 mm stones. I find that I can superglue the rough to the end of a nail that has been ground flat. Once you are done polishing, you very carefully heat the nail as far away from the stone as you can until the stone falls off. This works as long as the stone isn’t damaged by the heat. Agate can probably take it. I have also used regular dopping wax, museum wax and even red pitch on the end of a nail, sharpened dowel or pencil to hold the stone as you work on it. In the end, whatever works, well works. Good luck…Rob

Hello meixner,

Thank You Thank You!!

That is a problem I was starting to have with some of the small beautiful stones I am working on. My fingers even with gloves were having difficulty holding these stones. Your suggestions really gave me some additional ideas. That is the reason I use a flexible shift, I can control it better. I have cut stones on regular sized equipment back in the 60’s and 70’s. I know this is much easier and I feel I have much better control. I have figured a way to make my own small sanding drums which has saved me a lot of money.

Thank you again, your suggestions are very helpful.

I wanted you to know that and say thank you.


I often say that, with a few exceptions, there is no one right to do most of what we do. If you find a way that works for you, then do it. Most of the small stones that I cut are in the 4 - 8 mm size range and are almost always round. I can’t hold them freely in my hand nor do they lend themselves well to a traditional wooden dop and dopping wax. What works for me is to trim the rough down to be close to the size that I want and then grind and sand one smooth surface that will be the back of the stone when done. I superglue it to a mandrel of some sort. It may be a nail head or a nail cut down and filed square or a custom mandrel that I have turned on my small lathe. As long as the round end of the mandrel is equal to or smaller than the desired finished size of the stone it will work. Holding the mandrel in my hand, I then work the rough stone until it is kind of round on the sides but still flat on top. Then I chuck the mandrel in a cordless drill, pull the trigger and hold the stone to the grinding wheel carefully preshaping it. This goes fast because the surface speed includes the speed (RPMS) of the drill since I am left-handed. You would have to run in reverse if you are right-handed. Then it is just a matter of working my way down the grinding, sanding and polishing wheels until it is done and hopefully something like the size that it is supposed to be. If not, I just adjust the stone or the bezel when it comes time to set it. This works for much larger stones too, as long as they are round. You then hang the stone attached to the mandrel from a pair of tweezers, I use third hand tweezers with a base. Heat the nail with a soft flame until the stone falls free. Be careful what you let it fall on. Most harder fine grained stones seem to take the heat, but there are some softer, coarse grained ones that don’t. Freeforms are all done by hand if they are big enough to hold and more common cabochon shapes are done with dops and dopping wax. All this is a lot of fun. Good luck…Rob

Good Morning Bob!

It sounds like you have experimented over the years like I have. As you said it is great fun and I find myself always learning. I enjoy doing free form myself. I enjoy trying to see how mother nature has created the stone and they all seem to have their own firm or design. Here in Michigan we have the Great Lakes to enjoy. As the glaciers over the millions of years have bought tons of rock to the Great Lakes to tumble and to be found, there is treasure trove of different stones to found and worked with.

Thank you for sharing, have a nice weekend.



Rob I apologize!!! I said Bob, didn’t mean to do that.



I have been Bob to many. I found most of my semiprecious rock rough in my Mom’s cellar. I inherited over 2,000 lbs. of it when she died. Dad had collected for years and never really did much with it. I have given a lot of it to our local rock club and to the school district in which we live. I have enough to last a long time. I am nearly 72, so it will be our boy’s burden to bare when I am gone…Rob

Another thing you should be aware of is some agates are radioactive so it is very important to be clean. I have bought agatized minerals many many times that are radioactive. The lapidary feild is filled with old-timers that are the kinds of people that think just because theyve done something and haven’t died then its 100% healthy. Many of the people are poorer and older rural types that don’t believe in safe practice. Prior to cutting any rough, I have my geologist research scientist friend check out the pieces with his Geiger counter and 2 other types of radiation detectors that detect the other types of radioactivity that Geiger counters cannot test for. You’d be surprised how many pieces are unsafe. I purchase a lot of small pieces of rough for stone inlay work and about 1 in 30 pieces I can’t use. I’ve also bought many jaspers and agates from the same finds/types that weren’t radioactive but then other samples were. For anyone doing this in the future, please work outside and with a p100 respirator at the minimum. Radioactive dust is not just harmful if breathed in the way silica dust is but if you simply touch something and then touch your face or eat you can destroy your health.