A lapidary saw is a machine that cuts gemstone material with an abrasive saw blade. Generally, lapidary saws feature a motor-driven diamond abrasive blade, a vise or clamp to hold the stone, a material feed mechanism, and a lubrication system.
Visit a lapidary shop and typically you’ll see a slab saw and a trim saw. These are the two most common lapidary saw configurations but there are other interesting machines that do useful things as well.
Slab Saws
Slab saws are great for cutting stone slices. This agate slice is translucent held up to light.
Slab saws are used to cut slices off of rough rock, cut open geodes, and trim bigger rocks down into smaller shapes for further processing. They have circular saw blades with diamond grit embedded in the perimeter. Typically, the saw blade, lubrication system and material feed mechanism are enclosed in a cabinet with a hinged lid.
The stone is clamped in a vice on the feed carriage which slowly moves the material toward the stationary saw blade. Once the stone has moved through the cutting blade, the cut piece falls off and the material has to be re-positioned for another cut.
This saw has a transparent lid that shows the cutting in action. The cut rock falls off at about 2:24.
A slab saw without a mechanical material feed. This saw would also work well as a trim saw.
Trim Saws
Instead of relying on a mechanical feed carriage trim saws are set up for manual feed by the operator. These saws are smaller and have thinner blades than slab saws but they are similar in that the blade is stationary and the material is pushed into the blade for cutting.
Trim saws are intended to trim stone slabs and slices into rough shapes for cabochon cutting and lapidary carving.
A cabochon preform is cut on this trim saw. The operator is guiding the material into the blade manually.
Drop Saws
Another good machine for slabbing is a drop saw. Instead of mechanically feeding the material into a stationary saw blade, the stone is clamped in place and the rotating blade is lowered into it by an arm attached to a pivot point.
These saws can have functional advantages over slab saws when cutting difficult materials such as jade.The blade is pushed down against the material by gravity with the option of adding or subtracting weight depending on the stone material.
A drop saw making easy work of slabbing coprolite
Band Saws
No other lapidary saw can produce detailed cuts in gemstone material quite like a band saw with a diamond blade. Band saws designed for cutting stone are equipped with a lubricating system to keep the blade cool and clear the kerf.
Diamond band saw blades are shaped like a rubber band. The cutting surface on one of the thin edges of the band is embedded with diamond grit. The wide inner surface contacts and is driven by two wheels, one of which is motor driven. Cutting material rests on the table which is perpendicular to the blade. Material is fed into the blade manually.
Watch how some common lapidary materials are cut with this diamond band saw.
Ring Saws
Similar to the band saw, the ring saw can be used for cutting intricate details in gemstone materials. However, the blade is more rigid than a band saw blade and takes the form of a thin, circular ring.
A series of small wheels drive the blade and also keep it aligned and in place. The blade is encrusted with diamond grit and depending on the saw design it can cut in any direction. This means it usually isn’t necessary to turn the slab in order to make a curved cut.
Ring saws work best on thinner slabs due to the circular profile of the blade and corresponding circular kerf. The thicker the slab the more pronounced the circular kerf will be. It is possible to use this shaped kerf to ones advantage by cutting at an angle when preforming cabochons.
Demo of jasper cutting on a ring saw by Youtuber Kate Richbourg. Skip ahead to about 17:00 where the stone cutting gets going.
Wire Saws
Imagine mounting a loop of metal cable onto a band saw frame instead of a band saw blade. This is how a wire saw functions. If this cable is covered with diamond grit then conceptually you have a wire saw.
Although small sized wire saws are not commercially available for use in a lapidary shop, large scale machines are used extensively at quarries and stone yards where it would be impossible to use other types of saws. It’s worth mentioning here because at some point it may become a practical lapidary saw technology for small shops if some enterprising individual decides to develop a good tool.
The wire saw concept demonstrated at a stone yard