Engineering a New Saw

Paul and I are heading out for vacation in a couple days and with that on my mind I have been unable to think of anything really great to write about for this month.

I thought , “go back and look at what you have written on before and see if that gives you any ideas.” Wow, I knew we had been doing the magazine for a while but we are at 91 months. That’s a pretty long run and we will keep on going of course.

The one thing I have been thinking a lot about is making a new saw. I have been using the current one for many years. I have gotten some ideas and seen some innovations on commercial saw that I think are nice and its time to build a new one. I like the idea of lowering the specimen onto the blade instead of feeding the specimen through the blade. And I have been thinking for a long time about being able to rotate the clamped specimen so that I can cut the entire circumference then work into the middle gradually. I have never liked the way the edge breaks off at the end of the cut. It makes for more lapping and it chips out a portion of the fusion crust. But, mostly rotting the specimen will allow me to have less blade drag during the cutting. Right now I have to really watch the feed rate or the blade will stall. On bigger stones the area of blade contact gets really large. The .006 thickness blades want to stop with any feed rate faster than dead slow when there is a lot of contact surface. I know if I was using a coolant other than distilled water it would be better, but with meteorites that is not going to happen. So rotating the specimen will let me spiral in to the middle and give me better control. It should also control blade drift and keep from making curvy cuts.

I will need a special rock clamp and am still thinking about that. I am about ready to make a three prong vise sort of like a reverse gear puller. It will be compact in size and be what is mounted to rotate. The entire vise assembly will lower down past the blade. More of the blade will be exposed so it will be a messy saw without covers. That is a part that really troubles me. I don’t like getting so exposed to the wet nickel rich mud, and getting soaked with coolant is annoying but I like to catch the slice as it comes off the saw. So I guess I will have to make some kind of cup like device to have the slice gently fall into when the cut is completed.

I thought years ago when I made the current saw that I would be ok with the occasional large meteorite that I would have to make a few cuts on with the larger saw. But, I find now that we have many larger meteorites to cut that can not be sliced on the current trim saw. I do not like making cuts with the full thickness blade on the big saw. But, the saw I built a decade ago and have written about will not handle chunks bigger than a couple inches thick. That was OK for most of what we had to cut back then. Now we have big NWA’s to slice and I have to make many cuts on the big saw to reduce them to chunks that will go on the trim saw.

I waste about an 1/8 of an inch in each of those cuts on the big saw.

If I have near three inches of blade exposed above the deck of the saw and rotate the specimen in the clamp I can cut 4-5 inch thick meteorites without ever resorting to the big saw. If I arrange the whole clamp and lowering mechanism so that is will also move laterally in and out from the blade then I can make repeated slices of any thickness without reclamping the specimen. I have been utilizing a micrometer system for years to gauge the thickness of slices and that is even easier to continue with this new saw scheme.

I could probably invest in a commercial saw but frankly there is always something that I want to do that no commercial machine will handle. That was the reason for me making the semiautomatic machine I have now. But, I never was trying to cut 6 -10 kilogram meteorites a decade ago. Now my cutting schedule is fuller and my time to do it more restricted. I need to get streamlined and efficient again. I can easily move the stepper motor drives over to the new saw for automated feeding and two pullies and a belt can be driven for rotating the specimen. I think I will stay with the pumped distilled water coolant system I use now, where the water is squirted directly onto the blade rather then filling a sump with coolant. It is less messy in the long run and less wasteful of distilled water.

I have thought for a while about putting a water filter and purification system in the garage and I think I will do that. A small faucet system is cheap and will make all the water I need. I really only need to get rid of the chlorine. Especially since the slices are immediately moved to desiccant after cutting.

My biggest problem is deciding the main drive for the blade. I am using a small belt drive with a rather tiny AC motor that I speed control with a Variac. I am afraid that is will not have the power I need since it does stall rather easily in the saw I have now. I have lots of motors to chose from but not many that will run well with changing the voltage for speed control. I have some DC motors too and one of them my prove to be a better choice. The power supply for that will be easy to make also.

The hardest part of the entire project will be the rock vise itself and the support that lowers it past the blade. But, I think I have figured it out. It is the support that can not have any flexure that I am concerned about. I am going to hang a lot of weight out off the end of the clamp and want it to rotate but it can not dip at all because the blade would no longer be inline with the kerf on the other side as it rotated. Also as the weight comes off with removing slices the support must always maintain a constantly perfectly perpendicular orientation to the blade. No relaxing or sagging can be allowed in the support. Centering the meteorite mass between widely spaced support frames that run on heavy treaded rod for lateral movement across the blade will do it but it will take some engineering and precise welding and brazing.

I am really looking forward to starting the construction of this saw. I will keep you posted with pictures in a future article. Maybe by issue 100 of the magazine I will have it completed. Time does fly by so I better get started. The meteorites will not cut themselves.

Till next month, Jim

As always if you  have something to tell me you can reach me here jim@meteorite.com

About the Author

James Tobin
The Meteorite Exchange, Inc. was born in 1996 with meteorite.com and Meteorite Times Magazine in 2002. Still enthusiastic about meteorites and all things related to them, we hunt, collect, cut and prepare specimens. We travel to gem shows and enjoy meteorites as much now as in the beginning. Please feel free to share any comments you have on this or any of our other sites.
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