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Rock Saw Ideas


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#1 Ramo

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Posted 10 August 2008 - 05:35 PM

I saw a guy at a flea market the other day with a home made rock saw that consisted of an electric motor, attached to a saw blade that was in an old ammo box, and he was cutting rocks just fine with it. Has anyone made their own rock saw, or does a tile saw work? I have some agates I would like to cut, and I thought a saw would be handy for removing large pieces of matrix from fossils.

Anyone have any ideas on this subject?
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#2 Guest_solius symbiosus_*

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Posted 10 August 2008 - 05:52 PM

A wet saw(tile) should work just fine for cutting agate, or any other stone.

#3 Auspex

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Posted 10 August 2008 - 06:12 PM

Agate grade (diamond) blades are the major expense; if you make a wet saw, be sure to match the RPMs to the blade recommendations, and build it tight so it doesn't wobble. Otherwise you'll quickly spend more on replacement blades than you might have saved with a home-made vs. quality commercial saw. For trimming shale or (soft) limestone matrix, slower speed with cheaper carbide-tipped blades should do fine. WEAR GOGGLES! Even your best Ghost Dance shirt won't protect you here!

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#4 Ramo

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Posted 10 August 2008 - 06:19 PM

I'm going to try a tile saw from Menards, for trimming limestone, and I'll try a couple small agates on it to see how they go. Thanks for the imput!!
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#5 Guest_solius symbiosus_*

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Posted 10 August 2008 - 06:22 PM

The price of a good blade has dropped considerably over the past years, but they are still expensive.

For occasional work, one of these would probably suffice ... for a while anyway.

http://ww2.harborfre...function=Search

#6 tracer

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Posted 10 August 2008 - 06:59 PM

I've used rock saws quite a bit, and I can't say I'd ever recommend a tile saw for agates, unless you're talking about trimming a thin slab of agate already cut by someone with a larger saw. When I cut agates, if the stone doesn't already have good grabbing surfaces on the sides, I use a diamond wheel to grind flats on either side, so that I can lock the stone securely in the "vise" attachment, that is connected to a screw which feeds the stone into the blade at a fixed rate. The diamond blades are oil cooled and lubricated, and a hood closes to keep the oil from being slung everywhere. If the rock isn't tightly secured, it can come loose and bind and ruin an expensive diamond blade. If the blade doesn't run perfectly true through the stone, you end up with a stone that then has to be worked a lot on a flat lap with coarse grit to get the surface perfectly flat for polishing. Many agates will polish very well, but not with shortcuts and not without the proper equipment. Once I've cut the stones, I usually run through a lot of different diamond grits on watercooled wheels and then final polishing on a flat lap with cerium oxide. Typical grits would be 60, 120, 240, 600, 1200, 3000, 8000, 14000, and then polish. If you try to take shortcuts, you end up with lines in the surface from the coarser grit that you didn't polish out before you went finer.

You can get by with borrowing someone's big rock saw for an afternoon and cutting your slabs so that you can then work with something like a trim saw and then a genie-type wheel system, at a minimum. I can tell you that some material just never polishes well, and always looks hazy. Petrified wood has very great variation in how well silicified it is, and some of it will really take a polish and some of it won't. Some stuff is just a waste of time. Non-homogenous stones require good technique, because the material varies in hardness. If you just want to learn about such things, buy a cheap tumbler and collect a bunch of different small rocks and try tumbling them. You will learn what polishes and what doesn't. It really helps to have someone show you how to do this stuff. Especially if you want to do things like cabochons. That involves hard wax dopping the trimmed stone to a dopstick and a certain degree of technique on the wheels to have it come out well done and symmetrical.

Back to your original question - you could hand trim a small agate on probably any cooled diamond tile saw, but the surface won't be pretty and you still have the problem of getting it well polished to look cool.
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#7 tracer

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Posted 10 August 2008 - 07:03 PM

just re-read the other posts. a water-cooled saw would be better for limestone fossil matrix removal, because it won't stain the remaining matrix. limestone is much softer than agate and doesn't polish anyway, so you trim off what you want to and then you're pretty much done, unless you want to carefully use an airscribe or other instrument to try to recreate a more natural-looking surface than a saw cut. I've used saws to cut stand-up flats on fossils in matrix, and it works great.
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#8 Ramo

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Posted 10 August 2008 - 07:15 PM

Thanks for the detailed reply Tracer. I'll probably just use the tile saw for cutting limestone matrix. I do have a bunch of Lake Superior and Field agates I would like to have cut, so I think I'll find someone with the proper equipment and make some kind of trade, or just pay to have them cut.
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#9 PaleoRon

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Posted 10 August 2008 - 08:16 PM

What kind of Kansas shark teeth would be involved in this agate cutting trade? Ptychodus? Cretodus? Cretoxyrhina? Do you just need them cut, or cut and polished?

#10 tracer

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Posted 10 August 2008 - 08:18 PM

Bowkill - I'm sorry to not have been encouraging on the simple, cheap solutions. I do think it's possible for people to make their own wheels and saws fairly economically, but the diamond blades and wheels just aren't cheap. I tried doing hand polishing, dremel tool polishing, etc. I also have hand-held lots of relatively small (2" or less) stones and carefully fed them through both water-cooled and oil-cooled trim saws. You can take a very well-cut stone face and spray something like gloss Krylon or use a lapidary epoxy or something on it and it will look OK, but not great. Even with all the proper equipment, some people who don't have very good "eye" can't seem to do a decent cabochon. I have a medium eye, I think. I'm no artist. The picture below, with the exception of the crinoid necklace, has all agate material. The freeform on the left is apparently fenestrate bryozoa in agate, which I found in the vicinity of Livingston, Texas. It's a good example of something that was hard to work, because the "mat" wasn't level in the agate, so it was hard trying to expose it everywhere without cutting through it anywhere. The ring is silver hand-cast, believe it or not, in a mold made of cuttlefish bone. The backplate of the setting was an old silver quarter. I had to use commercial sheet silver bezel material for the bezel. The agate illustrates another difficulty of cutting cabochons. It's a west Texas moss or plume agate with a little "geode" crystal pocket in the middle of the stone. The problem there is guessing and hoping how the pocket will end up when you try to center it in the stone as you remove material. The next item is a Brazilian agate ring, and making those is just sort of a pain. I carefully used a diamond hole saw (core drill) and a pan of water and block of wood to drill the hole in a slab of agate. Then I had to cut and polish away everything that didn't look like a ring, without breaking it. The last thing didn't photo well but it's just a pretty little Mexican agate. I guess my point in showing the things is that I couldn't have done any of them without having access to the right tools. But I do really like agate, and although many of them are nothing special inside, some of them are amazing, and it's fun cutting them and seeing what you have.

agates.JPG
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#11 Ramo

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Posted 10 August 2008 - 08:33 PM

PaleoRon, I don't have many Cretoxyrhina, and Ptychodus teeth, but I do have a few "extra" Squalicorax and Scapanorhynchus teeth around I could part with. Do you have the equipment to cut AND polish, or just cut?
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#12 Maryland Mike

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Posted 10 August 2008 - 08:38 PM

Solius suggestion to look for saw blades at Harbor Freight is a good one. If you have one in your area, get on their email list and watch for thier diamond blades on sale. They put them on sale periodically as well as diamond burrs and bits. You probably won't find them any cheaper elsewhere for a tile saw, at least when they put them on sale.
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#13 tracer

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Posted 10 August 2008 - 08:59 PM

Without mentioning any companies, I have tried using cheap diamond core drills and saw blades and haven't been at all satisfied with the result. All diamond tools are not the same. You can buy a 3/4" core drill ranging from maybe $8 to around $100 or so, and just from my saying that, you have to ask yourself, what's the difference? Well, I own both and used both. The cheap one, first of all, probably should have been called a "burr" instead of a drill, and it turned out not to cut a 3/4" hole. The bit may have been 3/4" starting out, but when someone brazed the diamond grit onto it, it got bigger. The expensive bit has diamond grit sintered throughout its face, so that more diamond is constantly being exposed as the bit wears, and the bit face was turned to the exact dimension after the grit was sintered into it, so it is precisely machined, and doesn't chatter or wander as much. It cuts a much smoother hole.

I guess it depends on what you're trying to do. If you have quite a few rocks to cut, and they're important to you in any way, then just be careful not to mess them up. It's really annoying to cut a rock and then look at it and realize the blade wasn't cutting well and running true.
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#14 PaleoRon

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Posted 10 August 2008 - 11:00 PM

PaleoRon, I don't have many Cretoxyrhina, and Ptychodus teeth, but I do have a few "extra" Squalicorax and Scapanorhynchus teeth around I could part with. Do you have the equipment to cut AND polish, or just cut?


I have a pretty decent setup. I have a slab saw, a trim saw, and a six wheel polishing unit that goes from 80 grit to around 14,000 grit. All of my equipment uses diamonds to cut and polish. I don't have a flat lap so anything I polish comes out with a dome and it's hard to polish anything over 1 1/2 inches across without losing a lot of the material. I am no expert cutter, I just dabble in cutting and polishing when it's too cold to dive for fossils. Here are a couple of pics of some stuff I messed around with. The banded Botswana agate was broken with a kind of a point so I had to cut it with a really high dome to get it to look ok. I hope the pics don't look too bad.

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#15 jax

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Posted 10 August 2008 - 11:52 PM

Solius suggestion to look for saw blades at Harbor Freight is a good one. If you have one in your area, get on their email list and watch for thier diamond blades on sale. They put them on sale periodically as well as diamond burrs and bits. You probably won't find them any cheaper elsewhere for a tile saw, at least when they put them on sale.

Harbor Freight has a 7 in diamond wet blade on sale for $19.99. You can get a a 1.5 HP tile saw with stand including 7in diamond blade for $199.99

I have had my eye on one of these. I have a few septrian nodules I would like to cut and polish.
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#16 tracer

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Posted 11 August 2008 - 06:05 AM

Jax - Make sure if you buy a saw that there's a way to get enough of the blade protruding to cut through the thickness of whatever it is you want to cut. If you buy a machine set up to cut thin stuff, then you might have difficulty dealing with a septarian nodule. P.S. on cutting those - some of the ones out West are very "agatey" and polish well. All of the ones I've seen from Texas were more like mudstone with calcite crystals and for those all I do is break them open and display them as is, since the material won't polish.
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#17 bone digger

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Posted 11 August 2008 - 11:26 AM

I bought a cheap $60 tile saw and it works great on any rock I've tried it on.

#18 PaleoRon

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Posted 11 August 2008 - 11:49 AM

The trim saw I use is the 6 inch rock rascal. It is a really good unit and you can get it with or without a motor. Here's a link I pulled up that shows the saw. It's about half way down the page.

http://www.rockpeddler.com/pg23.htm

#19 Jack the Collector

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Posted 13 August 2008 - 03:48 PM

I have saws from 18 inch down to 4 inch,each has its own use for what it cuts.I did over a year ago buy a "tile" saw that has a diamond blade from Home Depot,its called a workforce saw(7 inch blade) for $79.00 plus tax.I agree with all tracer stated in his post,but I have to say the workforce is a work horse.I give it a serious workout and then some.My main intent was for it to be a trim saw,now I use it to slab smaller rock as well and have not yet changed the blade!Naturally there are conditions to making such a saw a useful long lasting tool.I never rush any stone through,always take my time by keeping an even steady pressure on the stone.I make sure the blade stays very wet...and so am I after I am done using it.If you use water only,make sure to get the blade dry after use.....I however use a anti rust agent/coolant(mixed with water) in my water basin.The first few cuts should be made with a soft material,a brick or sandstone is best to brak it in.Both are what you need for "sharpening" the blade when needed.

Jack
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#20 tracer

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Posted 13 August 2008 - 09:20 PM

"Lots of the members are fossils themselves and the ranks aren't being replaced by younger folks."

Ouch! Are you like, young dude?
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