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| Smaller 3 Head Machine |
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| Very Good at Polishing Marbles |
This 3 head machine uses 145 RPM gearmotors with just enough torque to make small spheres. I would
not recommend using this machine with steel cups and silicon carbide grits because I think it is too slow. But, with
diamond cups and a water drip, as pictured, the speed doesn't matter much because the machine can be left to run untended
for the 30 to 45 minutes that each stage takes. It easily makes spheres up to about 2" with the right size cups.
This machine comes with a water drip system (no bottle) and a set of diamond/resin cups, including 150 and 800 grits and a
set of wood polishing cups. I charge $160 for this machine, including shipping.
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| 2 Head Machine |
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| These are Core Drills Modified to Use as Grinding Cups |
This 2 head machine, with the modified core drills, is very good and quite fast at the initial rounding
of a sphere rough. It can make round a 1" quartz sphere in less than 5 minutes! It does not include a water drip
tube since the 2 head configuration requires attention most of the time anyhow and because it is so fast. These particular
motors are 180 RPM gearmotors that, unfortunately are not very reliable. It seems that, the larger the sphere, the faster
they fail. I have been using these particular motors on this machine for more than 3 years with no problem but other
machines have had the motors fail early. Replacement motors are available, online, for $4.95 from my source. I
sell this machine, with one pair of modified core drills, for $ 140, including shipping. The core drill pair can
be sized from 12 mm to 32mm. Personly, I don't do much smoothing or polishing on the 2 head machine, but those cups
are available.
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| This Machine is Capable of Spheres up to 5 Inches |
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This machine is capable of spheres up to about 5", maybe bigger. These are 60 RPM gearmotors.
This picture shows a set of polishing cups that use rings cut from flexible diamond/resin polishing pads. This method
of velcro-attached rings is very convenient and works very well for the larger spheres but not very good for spheres under
about 2.5". I recommend doing the coarse grinding with diamond cups which could be brazed or which could be made from
those grinding cups used for granite surfaces. The granite grinding cups can be 2.5", 3", 4" or even 5" in diameter
and are quite a bit less expensive. The cost of this machine with a water drip, but no cups would be $160 plus $25 shipping.
The cost of grinding and polishing cups will depend on their size. This machine could be used with pipe fittings as
grinding cups with silicon carbide grits, as well.
| Rock Grinder with 4" grinding cup |
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When you make spheres, even small ones, it is almost always necessary to do some grinding on the rock to
make it ready for the sphere. I have found that these small motors with this 4" grinding cup will do a good job
of shaping sphere roughs up to about 2.5". I'll sell you this machine, with a water drip tube, for $90, including
shipping. If you are into making cabs or want to make larger spheres, this grinder would not be suitable, but it does
do a good job on the smaller ones.
| 6 Inch Swing Arm Rocksaw |
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| Very Convenient for Sphere Preforming |
This little swing arm saw can use a cheap (less than $3) diamond blade and is very convenient for the preforming
of spheres. As you can see, the rock is clamped in a manner that allows you to easily cut a cube, if you wish, or to
cut directly a hexagon or octagon shape that can be re-clamped to make the other cuts for a sphere. It is not real powerful,
but you can cut a 2" sphere preform in a fairly short time. Maybe as little as 30 minutes for an easy cutting material.
It sets in a dish pan (not included) and uses an aquarium pump (included) for the water flow. I certainly would not
recommend this saw for preforming large agate spheres, but it really does a nice job on the smaller ones. I can
sell this saw for $130, plus $15 for shipping.
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