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Beginning Lapidary, Part 1: Cutting Cabochons

Learn what it takes to make a cabochon, and the best saws and techniques to use for the job

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Why bother with cutting your own stones?  I mean, there are plenty of beautiful stones available for purchase already. But if you’ve ever had that idea for a piece of jewelry that you have yet to create simply because you haven’t found the right stone for it, then you’ve already felt the pull of lapidary. Imagine having the ability to custom cut and shape your own stones! 

I know the equipment can seem intimidating. But once you know some basic terminology and tools, you’ll be surprised how quickly the rest will follow. Consider this primer your first step toward cutting gorgeous stones.

What it Takes to Make a Cabochon

Shown below are the basics steps needed to turn rough rock into a cabochon; each step requires a different lapidary machine or unit.

If you don’t have all the equipment, you can skip some steps to get started right away. For example, if you don’t have a slab saw, skip the rough stage and purchase pre-cut slabs. 

By working with what equipment you do have, you can start cutting stones while building your lapidary setup piece by piece.

Lapidary equipment_cabochon 1
STEP ONE: Rough rock stage
Acquire a chunk of rock as it comes from the ground.
Lapidary equipment_cabochon 2
STEP TWO: Cut slab rock stage

A slice of rough rock; the thickness of the slice determines final height of the cabochon.

 

To make this, you need:

 

A slaw saw to cut slices from a rough rock. Or, skip it: If your rough rock is small enough, you can trim or grind it directly.

Lapidary equipment_cabochon 3
STEP THREE: Trim & grind the preforms

A piece of slab trimmed to size, prior to final shaping; the shape of the preform matches final outline of the base of the cabochon

 

To make this, you need:

 

A trim saw to cut preforms from slabs, and a grinder to shape the preforms. Or, if slab is small enough, you can grind and polish it directly.

Lapidary equipment_cabochon 4
STEP FOUR: Grind & polish the cabochon

A final shaped and polished piece of stone that is now ready to be set into a piece of jewelry.

 

To make this, you need:

 

A grinder to shape your preform into a cabochon, and a polishing unit to shine it. Or, skip it: Some preforms, (such as raw gem drusy) need little to no grinding or polishing.

Quick-Start Guide to Basic Lapidary Machines

Good to know: Lapidary saws require special oil-based or water-based lubricant to cool and lubricate the saw blade as it cuts through the stone. Consult your manufacturer’s instructions for recommended lubricants.

The lubricant is generally held in a reservoir under the saw’s cutting table. The bottom of the saw blade dips into the liquid. As the blade spins, it picks up the lubricant, continually delivering it to the slice being made through the stone.

A good guideline for ideal saw operation (whether slab or trim) is to ensure that your blade is approximately 3 times as large as the stone that you’re cutting. If your stone is too large for your blade, the friction could harm your machine or break your blade.

Lapidary equipment_saws 1

Trim Saw

  • Cost range: $150–$2,000
  • Purpose: Used to cut or trim slabs down into usable pieces of stone called “preforms”; can also be used to trim pieces of stone to shape for inlay, intarsia, etc.
  • Good to know: Trim saws only cut straight lines. To make a curved line, you need to make a series of overlapping straight cuts first, and then complete and refine the curve using grinding wheels.

Slab Saw

  • Cost range: $700–$15,000
  • Purpose: Used to cut medium and large pieces of rough rock into manageable slices called “slabs”
  • Good to know: To achieve even slices through the rough, slab saws make use of a feed system. An adjustable clamp is used to secure the rough rock and keep it straight in the machine. This clamp slides along a track, slowly pushing the rock against the cutting surface of the saw blade. Large slabs can take hours to cut, so for a large saw, an automatic feed is nearly essential. 

How to buy saw blades 

Saw blades come in a variety of sizes, thicknesses, and “kerfs” (the width of the line that is cut through the stone by the saw blade). The kerf is generally wider than the blade’s thickness due to abrasion. Match the thickness of your blade to the type of stone that you’re cutting. Hard stone needs a thicker blade that is less likely to break; valuable gem-quality stone benefits from a thinner blade to ensure a less wasteful kerf.

There are two types of cutting edges: sintered and bonded. Sintered blades contain abrasive throughout the cut-ting edge, helping them last longer. Bonded blades have abrasive bonded only to the exterior of the cutting edge and are generally less expensive than sintered blades.

Decode those numbers 

Saw blades have four measurements: outside diameter, blade thickness, arbor hole, and kerf (cutting width). You’ll need these numbers to buy the correct blade for your machine. 

For example, the above saw blade has:

  • 4"x.004x1⁄2x.007  
    • a 4-in. (10.2 cm) diameter
    • a 0.004-in. (0.10 mm) blade thickness 
    • a 1⁄2-in. (13 mm) center arbor opening 
    • and a 0.007-in.(0.18 mm) kerf

    For more information, view our lapidary glossary page

    Ready to invest in your own equipment? Check out this list of manufacturers and suppliers to start you on your way. 

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