[meteorite-list] Lessons from the Saw - Cutting Meteorites for Newbies and Curious Onlookers

From: Galactic Stone & Ironworks <meteoritemike_at_meteoritecentral.com>
Date: Sat, 29 May 2010 19:14:50 -0400
Message-ID: <AANLkTikE5xC5-f41n__JZl5rH6TgX82Ki_jTb6I7Xnes_at_mail.gmail.com>

Hi Listees, Listoids, and Lurkers!

I just past my first anniversary of owning a lapidary saw and I am
preparing to cut some unidentified NWA material that is likely a
howardite or eucrite. Cutting material like a howardite is very
different than cutting something harder like most H-chondrites. This
got me to thinking - I often asked the List about various aspects of
cutting and polishing, and rarely would I get any useful answers. A
small handful of people did contact me in private to give me some
pointers, and I would like to thank them again for sharing their
wisdom with a rookie cutter. But, in public on the List, you could
hear crickets and see tumbleweeds blowing by as I waited for answers.
A long-time veteran collector and List member told me the reason is
because the skills involved when cutting meteorites are learned
through trial and error, and they are akin to "trade secrets" - no
successful cutter is going to divulge these techniques because it
amounts to helping out the competition.

Well, a year later, I am a pretty good cutter - or so I am told by
several people who have used my cutting and polishing services. I can
make nice even cuts and I can produce a hard polish that is mirror
smooth. Recently, I started shopping around my services as cutter to
collectors and dealers who don't own saws. In the process of doing
so, I had a lot of questions thrown at me - about cutting,
preparation, blades, coolants, sanding, polishing, etc.

This List has been very gracious to me over the 3 years I have been
here, so I wanted to contribute some knowledge back into the List -
for the benefit of the newbies, lurkers, and people who are
considering whether or not to purchase a saw.

First, 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, 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 area. 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
falling 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 do some more cutting and polishing. :)

Best regards and happy cutting!

MikeG

http://www.galactic-stone.com

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Mike Gilmer - Galactic Stone & Ironworks Meteorites
http://www.galactic-stone.com
http://www.facebook.com/galacticstone
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Received on Sat 29 May 2010 07:14:50 PM PDT