How To Make An Opal Cutting Machine On The Cheap

This was primarily a challenge of creativity, which is something I enjoy doing as a Mr. Fix-it kind of guy. It also helps that I have a very large accumulation of “stuff” for materials. If you want to build a wet grinding setup at very low cost instead of investing $800 - $1000 in a new grinding machine than this article is for you.

It is not intended that anybody attempts to duplicate what I have created but rather to recognize that you can “do it yourself.” I made errors but that is part of creative process and maybe you will learn as much from my mistakes as from the successes. This setup worked well for cutting my rough Opal that I had laying around.

opal cutting machine completed with bucket

So, let’s create a wet grinding setup. The first thing we need is grinding or polishing wheels, about 3-6 of them in different grits. I’ll leave the actual grit recommendations to others but let’s say something on the order of 100, 220, 400, 600, and then a flat plate for buffing.

If I had an open budget I would buy a new machine already set up and ready to go. Dropping down one notch, I would love to have new 8 inch diamond wheels but those suckers are really expensive at $175-$300 US each. A new 6 inch diamond wheels run $100-175. So if you are talking about 4 or 5 wheels, that’s real money.

Let’s go to the other end of the economic scale. I searched eBay for about a month or so looking for USED stone or diamond wheels. This is a bit tricky because there is some real junk out there. If somebody stopped using them, they did it for a reason. Please shop carefully. Ultimately I bought 6 wheels in varying diameters and grits and a flat plate from three different auctions and got all of that delivered for under $100.

The next thing needed is a metal shaft to mount the wheels on and pillow blocks to hold the shaft. I just happened to have a long 6 inch shaft and a pair of 2 inch pillow blocks on hand. Pillow blocks are the bearings the shaft rides in on the ends of the shaft. In retrospect, the 1/2 inch diameter was a poor choice since most of the stones had 0.5 or 1 inch holes. However, it was what I had on hand so I used it. Since I live on a tiny rock in the middle of 93 million square miles of salt water, I don’t always have the resources I’d like. Finding bushing for the big holes down to 1/2 inch was a challenge. Ultimately, they were all plastic, some pretty soft and not the best choice, but the only choice.

The next thing I needed was a sort of pan or tray to catch the water coming off the wheels. It needs to be something not made of steel. Don’t want to deal with rust. I had an old plastic pan lying around that was just a few inches shorter than the shaft I had so that seemed a reasonable choice.

The next thing was a spray shield. This again needs to be non-corrosive like plastic, aluminum, or copper. Checking around, I had an old section of very large copper roofing gutter. It had a really weird configuration but I just used several mallets and some muscle to change the shape into what I wanted. I cut it to length on a band saw and then used an angle grinder to make cuts to fold some end tabs.

Then I made a wood base to hold the plastic pan and spray shield in place. I added big wood blocks at the ends to mount the pillow blocks. I put it all together and mounted a pulley on the end of the shaft. I had an old ½ horse motor and put a 3 step pulley on that. Didn’t know what speed I wanted the wheels to run at so it was just, put it together and see what happens. This is what it looked like.

opal cutting machine

The next thing was to rig up a water supply for the wheels. Typically this is done with a water pump. However, the objective here is minimum cost so I went with the absolute simplest approach, a bucket with a drip line. The drip line is moved to the desired location by moving the paper clip. Yep, really, really cheap and it works great.

opal cutting machine with buket water gravity feed

After some trial and error, I decided I had too many wheels on the ? inch shaft and two of the wheels appeared to be out of balance or maybe the soft plastic bushings were out of round. For whatever reasons, there was some pretty severe vibrations, so I removed several of the wheels.

opal cutting machine completed

This is what I finally ended up with after 6 months of use and changes. There are three grinding wheels, a flat plate, a thin saw blade and two wire brushes. The flat plate is a worn out 1200 grit diamond. I used spray glue to attach a piece of 600 wet/dry silicon carbide paper from the local hardware store. CAUTION, use a VERY light coat of spray. Notice also I brought the cover down lower because there was excess water spray off the wheels.

If this were my only grinding machine I would have put a polishing pad on the flat plate.

This entire setup cost less than $100 because I had the “stuff” laying around to put it all together. It is quite sufficient as a basic machine and I can change the configuration or type and number of wheels at any time.

Forum member maulbuick

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