My New Meteorite Saw

I have had a great adventure the last couple weeks. My old diamond saw that I made about 30 years ago final died and I needed a new one. There is nothing on the market to go out and buy that will do what I want from a diamond saw. So I took a week or so to think about the design and made a few sketches of ideas and then spent the last week making the saw. Of course this was the last two weeks of March.

Paul said, “You have to take a lot of pictures for an article unless you are keeping the design a secret.” Well, there is no reason to keep it secret. There is nothing really new that was not in the other saw it is just a lot better. Thirty years ago I had to make a saw fast. I used a lot of welding on parts and used really scrap stuff from the garage to put the old saw together. Not this time.

I had the time to do this right and make it the way I wanted so I did no welding. No brazing either it is made from aluminum and a few hard wood spacers. The only plastics are the splash covers of clear acrylic and the motor and pulley cover and blade cover made of black ABS.

First let me say that I made nearly every part except the actual machine screws that hold it together. The aluminum plate and angle I had in the garage from taking apart some old pieces of printing equipment. I had been holding on to this metal from years ago when I got out of the printing business. The whole cost for this saw was under forty dollars and that is because I had to buy the pump for the coolant. I had two pumps but after sitting for 20 years neither worked.

I used the motor and pulley mechanism from the old saw since that part I had well engineered 30 years ago. But the broken belt that provoked this whole thing forced me to modify the pulleys. They were a strange double groove vee belt type deal that I could not find a replacement for anywhere. So I took the pulleys and turned them down to get rid of the middle peak and make them into a normal single vee design.

I had two thick aluminum plates that were the side frames from a huge old photo typesetting machine. They were 1/4 inch thick and would make a great saw top structure. There was a hole in the middle of the plates and I decided to utilize the hole for the coolant to drain off the saw. I have become annoyed too many times by having to drain the saw after use and having to pull the saw apart to change the blades. And then there are the times that the thin slice of meteorite slides right down into the coolant tank and I had to take the saw apart to retrieve the slice. So the plan for this saw was to spray coolant onto the blade and let it be completely exposed above the top of the saw structure; much like a commercial chop saw. I would have to recirculate the coolant and I needed to keep big pieces of rock out of the tub that would be under the saw. I did not want pieces of rock jamming up the pump. This will all be pretty easy to understand by looking at the attached images.

I had an old piece of electronic equipment that I had torn down but I had kept the case from and it had six round ventilation screens. I took those and made them into filter screens by placing them onto a plate of aluminum that covered the big drain hole in the saw top. So nothing big enough to clog my pump or coolant spray nozzle would make it to the tub that had the recirculating coolant. Also no slices or pieces of rock will ever fall anywhere with the new saw.

For years I have written about how I attach the meteorites to a mandrel with dop wax and make slice after slice by moving the mandrel over with a screw pushing mechanism. I am still using that system but this is much more refined. The new saw has much tighter tolerances and the whole mandrel motion mechanism can be removed and replaced with a table cutting platform for when slices are diced down to smaller size pieces.

I had used a rolled threaded rod of large diameter and coarse thread in the old saw. This time I machined the threaded rod for the mechanism that advances the stone into the blade. I used a small diameter shaft and cut fine threads into. It is much smoother and I have a lot more control and none of the periodic error that I had with the old rolled threaded rod. I would turn the handle to advance the stone and it would not move for half a turn and then it would advance the other half rotation. I have none of that with the machined threads I cut. The trade off for using a thin diameter rod however is that I have much less support in the whole carriage the moves forward and back. So to avoid any sagging when cutting a heavy rock I have installed an “antisag pin” from the bottom of the carriage to the frame of the mechanism below. The round end of the pin rides smoothly on the bottom frame rail and there can be no sagging under load. The addition of an un-threaded rod parallel to the threaded rod is another improvement. There can be no up and down or twisting motion of the carriage as it moves forward and back past the blade.

Since the whole blade was to be exposed above the saw top plate I decided that I could use an 8 inch blade as well as the 6 inch size I have been using. So I designed the blade cover so that it would have wide enough sides to cover the last portion of the 6 inch diameter blades and be thick enough to handle the 8 inch blades with some room to spare. I drew up patterns on cardboard and cut them out then transferred the contours to 1/8 inch thick ABS plastic and cut out the two sides. ABS plastic has a textured side and a smooth side so I had to turn the pattern over for one of the sides so they would both have the attractive texture when glued up. I made an assembly jig with a board and finishing nails to hole the plastic sides down in alignment and let me wrap the band of plastic around the edge for the top of the blade cover. I stacked blocks made of foam core the correct thickness in between the two side pieces and glued the assembly together.

I love working with ABS plastic it cuts easy and breaks straight if you score it on both side. And it glues together with solvent type glue so the pieces are welded as if they were one piece when it drys. I made the motor and pulley cover the same basic way. Patterns cut from cardboard and the pieces glued using my right angle picture framing clamps and small hobby speed clamps.

I had thought about making a fiberglass tank to contain the coolant within the middle of the saw. But decided to take aluminum angle and cut it and rivet it down to the saw top plate and create a wall. I had been storing a big can of assorted aircraft rivet for 30 – 40 years and had used a few from time to time but this was my chance to make use of them. The hard aluminum alloy rivets would give me a fantastically strong connection and would never rust. I also sprayed the inside of the wall area with a plastic sealer so the coolant could not leak.

I worked the project as sub-assemblies. I made the cross motion mechanism with the carriage and support as an assembly of its own. I had the motor and pulley and blade arbor mechanism as another assembly. I just needed to integrate the various sub-assemblies into the finished saw design. I already had the cross motion mechanisms and carriage made so I could mark the saw top plate for where it would be located. Then I cut and folded the coolant wall aluminum angle to leave spots where components would later be mounted.

Having the ¼ inch thick top plate let me tap all the mounting holes for the various items that needed to be mounted. I used mostly brass screws to avoid rusting but could and may switch them out for stainless steel screws. But I don’t think there will be much galvanic activity between the dissimilar metals of aluminum and brass. After all I am using distilled water with a little alcohol which is nearly electrically neutral for chemical action. And the saw should drain to nearly dry quickly after use. But, I did not want to use steel screws within the coolant tank area. I figure I will need to take it apart from time to time and do not want to fool around with corroded screws.

I had been annoyed with the old saw that it did not have nice knobs to turn for making the motion of the stone laterally or into and out of the blade. So I had some scrap exotic hardwood (the species I no longer remember, but it was nice wood). I turned it into knobs and think I made nice attractive contours that will make the saw nice to look at and pleasant to use. There is a knob that locks the aluminum mandrel holder into the cross motion mechanism. There is a knob that holds the mandrel in position after it has been moved over for the next cut. Two additional knobs were needed one for the end of the lateral motion adjustment screw and one on the crank of the forward and backward motion threaded rod. It took a lot of time to turn the knobs but I am happy with the way they look and work.

I was a lot more interested in the appearance of the saw this time. I was concerned that it worked well first off, but I wanted something that was nice to see also. Over the last 15 years I have been asked to cut meteorites on camera on two occasions and to be perfectly honest I was not proud enough of the saw I had to feel great when using it on camera. But, this saw I think is pretty attractive and well engineered.

The images will tell you the rest of the story on the construction. So I will move on the the next annoying part of the old saw I was going to try and remove from this design. I have cut rocks long enough to expect that there will be spray everywhere. But, I am tired of being soaking wet after a couple hours of work. So one of my goals with this saw was to make covers that would give me visibility while still containing almost all the coolant.

I was pretty sure that I could heat acrylic plastic and bent it using the heat gun I have for shrink insulation. So I made templates again out of cardboard for the size and shape of my shields and then cut them after they were correct from 1/8 inch clear acrylic. I heated the plastic with the heat gun then bent the straight folds of two of the shields using wooden blocks to apply pressure and make the bends. For the large shield that folds back out of the way on a hinge I heated the plastic and used the same template I used for the curve of the blade cover, but with some alterations to give me a drip lip on the front edge and a flat vertical portion to raise it to the correct height. It needed to be higher than anything else near the stone so I had plenty of room. I wanted the front shield to just be a little higher than the drip lip of the curved swing able shield over the middle of the saw. You can see the finished shields in the pictures. I made a shield for the left side of the saw just to keep the remaining spray that when in that direction but it needed no heating and bending.

The coolant needed to be squirted at the edge of the blade near where the stone was being cut. But I did not want a huge stream. So I cut off a length of copper tubing saved from an old refrigeration unit that I had saved the compressor out of. I needed a vacuum pump for high voltage rarefied gas illumination experiments 20 years ago. I cleaned up the copper tubing and formed it into a curve that mimicked the contour of the blade cover because it would be next to the blade cover when installed. I took a tiny tubular rivet from my clock making supplies and would use that as my nozzle for the coolant sprayer. It had an opening of only about 30 – 40 thousandths of an inch. It would nicely restrict the amount of coolant dispensed and make a good stream. I drilled a tiny hole in the side of the copper tubing near the end which I had bent to cross over in front of the blade. I soldered the tubular clock rivet into the hole and closed the copper tube with solder at the same time. Down at the other end of the copper tube I soldered a thick brass plate with two holes to the side of the copper tube to mount the copper coolant supply tube to the saw frame. The tube now very solidly mounted just needed a piece of plastic aquarium tubing and a pump to make it work.

There is little else to describe. I needed to change the AC electrical cord for the saw motor. After 30 years it was due for a change. I run the saw off a Variac to control the speed a little bit and have used the switch on the Variac, so I just made a waterproof plastic box on a plastic stand for the cord to motor wire connections.

So that is it, I got some 8 inch diamond blades that were still thin and put one on and made my first cuts. I picked one of the most fractured pieces of Al Haggounia that I could find and mounted it on a mandrel. I made seven cuts one after the other moving right across the width of the stone. The slices were so smooth that they almost did not need to be lapped. It cut with so little stress that the slices did not fall apart on the fractures. I got rock mud all over the saw but proved it worked. I keep it clean and probably always will because this may be the big home engineering project of my life.

I hope some of the readers found this interesting I know it was pretty far from the normal discussion of meteorites and probably was pretty dry stuff. But, maybe it gave some enthusiasts a few ideas for saws of their own.

As a fun experiment I got to the very end of a stone and decided to see if I could split the last remaining little bit attached to the mandrel. So here is a shot of that piece after cutting. The feeler gauge is .014 inches and the rock slices on each side are only about .028 inches. I left it slighted uncut so it would hold together for photos.