A Guide to Cutting Stony Meteorites

Before we begin, I want to give a little background on my own cutting, so this will give some context to the tips and pointers I am going to offer below.

I use a Lortone Rock Rascal 6-inch lapidary saw. I paid about $300 for it. It is now discontinued by Lortone, but they are still available for purchase from some vendors as NOS - New Old Stock. It is the only rock saw I have personally used. I like this saw. I did some research before buying it and I considered several alternatives before deciding on this particular saw. I could have bought a bigger saw and budget was not a constraint - but I went with the 6-inch saw because I don't have much desire (or opportunity) to cut large specimens. The vast majority of the specimens I deal with are about the size of a golf ball (or smaller), so a 6-inch saw was all I needed.

I cut frequently and I have cut several types of material. I have cut some rocks, shells, and other non-meteorite materials, but I will limit my comments to cutting meteorites and tektites.

Materials I have cut - every type of OC one can imagine, highly weathered materials, fresh materials, carbonaceous chondrites (several types), mesosiderites, howardites, eucrites, and indochinites.

I don't cut irons. It's too labor intensive, time intensive, and it's hard on the equipment. So all of the advice below is geared towards cutting stony-type meteorites and some mesosiderites.

DISCLAIMER : I am not claiming to be an expert and these remarks are intended as unsolicited advice for newbies who are curious about cutting or would like to learn more about cutting. I do not claim that my methods and equipment are the best choice on the market. I use what I have and it works for me. Your mileage may vary.

SAW and CUTTING TIPS :

1. Bigger saws require bigger blades. Bigger saws make more noise and mess. Get a saw as big as you need - don't buy a saw that can cut a basketball-sized meteorite if you don't have access to such meteorites. Consider what you are going to need to cut and then decide what size saw to get. Keep in mind - half of the saw blade is under the table surface. So, a 6-inch saw has approx. 3 inches of useable cutting surface. This means the biggest meteorite you can properly cut in one pass on a 6-inch saw is about 3 inches in diameter. Replacement blades for larger saws are more expensive - another reason to get the proper size saw.

2. Avoid home improvement tile saws. I call these "Home Depot saws". Yes, they are cheap. And yes, they will cut meteorites. But, the blades are thick and are made for cutting materials like ceramic tile. Loss is not much of a consideration when cutting tiles for your shower surround. But, using that thick tile blade on a meteorite will result in a wide cutting swath of lost material and money. It's similar to swatting a fly with a baseball bat. If you want to lose half of every meteorite you cut, then buy a Home Depot saw. If you want a razor-thin cutting swath and minimal loss, get a true lapidary saw. Further proof of this is to take a look at any successful or experienced cutter - all of them use lapidary saws. (unless they cut irons, and then many use wire or band saws)

3. Don't use tap water as a coolant. Tap water contains chlorine, which will contaminate the material and result in an unstable specimen. Use distilled water only. Distilled water is cheap. You can buy it at Walmart for less than $1 a gallon. With a small 6" saw, a gallon goes a long way. It's well worth the investment. Your specimens will thank you and the people who end up owning those specimens will thank you.

4. A .012" kerf saw is plenty thin. Loss with a .012" blade is very minimal. There are thinner blades available, but some of them will not work with all saws. For example, there are ultra-thin blades that are .006" kerf. These blades are floppy and must be rotated at very high RPM's to maintain their rigidity during cutting. Always check your saw motor speeds and the size of your pulley before using one of these ultra-thin blades. I have tried both, and the .012" is plenty thin for me while still being rigid.

5. Everyone has their own ideas about what type of blade is best. I have tried the CBN blades (cubic boron nitride) that are supposedly designed for meteorites, and I didn't like them. I find that diamond blades cut much better than CBN blades. So, IMO, forget about CBN blades. I use the DiaLaser brand diamond-coated blades and they work very well for me. My next couple of blade purchases will be experimental and I am going to try a sintered Pro-Slicer blade. I will report back in the future about the performance of those blades.

6. You can dry cut a meteorite. I just don't recommend it for the majority of circumstances. If you have a very small and friable specimen that will not react well to getting wet, then you can dry cut. Keep in mind, dry cutting is hard on your blade and will result in a dull blade much faster than wet cutting. But, replacing a $30 blade might be a worthwhile trade off if you are cutting something fragile like Orgueil or something very valuable like a lunar or martian. 99% of the time, I cut wet.

7. Don't be in a hurry. Cutting meteorites is not a race. The faster you feed the specimen into the saw, the more likely the blade is to wander, resulting in a crooked or wedged cut. Feed slowly, consistently, and evenly. Cutting in a hurry will only result in poor cuts that require more work later to clean up. It's better not to leave a deep saw mark in the first place, than to spend time sanding it out later - which also results in more loss of material.

8. Don't be afraid to hand cut specimens. I've hand cut hundreds of specimens and have yet to cut my hand or fingers. (knock on wood) There are a wide variety of options of available for clamping specimens into a vise or jig that will hold the specimen during cutting. These result in nice straight even cuts. But, all of them have tradeoffs. First, some specimens are odd shaped or small, and they are difficult (or impossible) to clamp into a vise or jig. If you don't have a vise or jig, don't let that stop you from slicing. With practice, it is possible to make straight even cuts by hand. I own a sliding vise for slicing, but I rarely use it. I find it much easier to just hold the specimen in my own hands and I get better feedback during cutting because I can feel the specimen during the cut. I'm not saying that hand cutting is the best way to cut, I'm just saying that it works for me in many situations. Ultimately, the specimen itself may dictate what method is used to cut it.

9. If you do cut by hand - cut slowly and evenly. Do not feed to hard or quickly. Do not force the cut. Let the blade do the work and watch the cutting swath closely, especially in relation to the blade. A thin blade can flex in subtle ways that is not readily apparent, and this can result in an uneven cut. When the blade wanders in this manner, you will end up with slices that have a taper or wedged profile. Also, don't try to cut slices less than 1mm by hand, unless you can live with some breakage. Perhaps I am not experienced enough yet, but when I try to cut super thin slices by hand, it rarely works out well - that is where a feeding mechanism like a vise or jig comes in handy.

10. I guess I shouldn't have to say this, but for the record - wear safety goggles or safety glasses while cutting. Even if you wear eyeglasses, be sure to wear some impact-rated eyewear over those. You will save your eyesight and you will prevent your eyeglasses from being damaged.

11. If your saw doesn't have a light on it, get a "clamp lamp" or similar light fixture and set it up to illuminating the cutting area - with a focus on the blade zone. An adjustable desk lamp or shop lamp is good for this. If you want to safely make nice even cuts, you must be able to clearly see what you are cutting. Don't assume your garage that is sufficiently lit to cut plywood is bright enough to do detail cutting on small valuable meteorites - throw more light on the subject.

12. Keep a magnet handy. I have a magnet on the end of a pencil-sized wooden stick. I prop this up on the saw table during cutting and it helps prevent specimens from getting stuck to the blade or falling into the tank. It's also handy to collect crumbs and specks during cutting. If doing the latter, put a tiny ziploc bag over the end of the wand - to easily remove the crumbs later.

13. That little slot in the saw table that the blade passes through is too wide. Get a piece of thin, flat plastic and cut a small slit into it that will barely accomodate the cutting blade. Shape this piece of plastic to fit as a "template" that will drop onto the cutting table and can be removed easily. This will help prevent thin slices and pieces from dropping through the slot in the table and into the murky depths of the coolant tank. This little modification will pay for itself the first time is saves a thin slice of a rare fall from slipping into the tank.

14. Let the stone dictate where to cut. The shape, composition, and size of the stone will usually determine where to make the first cut. Carefully examine the stone prior to cutting and have a plan in mind - don't just start cutting willy nilly. Take notice of any fractures in the stone which may effect the cutting - if you cut across or along a fracture, the specimen will often crumble or a slice may break. Take into account the weathering state of the specimen as this may also effect the cutting.

15. Often you will have two choices for cutting a specimen - cutting it in a way which will expose the most surface area on the slices, or cutting it in a way that will produce the most slices. An example is an elongated or thin (or flat) specimen - if you cut it lengthwise along the narrow profile, you will yield pieces with the most surface area, but you will get fewer pieces. If you cut it widthwise across the longest dimension, you will get a loaf of bread type of affair - many pieces, but with less surface area on each. Which route is best is determined by a variety of factors that the cutter decides.

16. Have your oven on at 225-240F in advance of cutting. After cutting, take the specimens and put them directly into the oven without delay. Bake for 4-6 hours minimum, to purge any moisture from cutting. Some people like to chase the water out with alcohol prior to baking, but I have had good results without using alcohol and now I rarely use it.

17. After you are finished cutting, empty the coolant tank immediately, and then spin the blade dry. Keep your saw clean and tidy and don't let gunk build up between cuttings.

18. Saw marks are difficult to avoid and can be laborious to remove. As I said above, cut slowly and evenly and you will avoid deep saw marks. If you do get saw marks, keep some sandpaper handy in various grits from 100-600 - these grits are easiest to find at Wally World or home improvement stores. Start at 100 for deep saw marks on robust specimens, start at 200 or 220 if you have a more friable specimen. Place the sandpaper on a hard, level, flat surface and then place the specimen "face down" onto the sandpaper - press firmly and sand the specimen in a circular motion. Don't press too hard or the specimen may break or chip.

19. If you don't own a lap polisher, keep additional sandpaper handy in grits from 600 to 1500. Jeweler's rouge is also good to keep around - to achieve those hard glassy polishes.

20. If you aren't in the mood, don't cut. If you don't cherish your cutting time and love what you are doing, it will show in the results.

That's it for now. I am off to prepare more specimens for Galactic Stone & Ironworks. :)