Discs and abrasives for roughing and polishing gemstones: which ones to use and where to buy them?
- Oscar Bautista
- 3 days ago
- 4 min read
Updated: 3 days ago
The information below applies to a wide variety of gemstones but does not apply to diamonds, as their cutting process is different.
In my daily work, I use three types of discs for cutting gemstones: roughing discs, faceting laps, and polishing laps.
The main difference between the diamond discs I use for roughing and faceting lies in the grit, and the choice depends on the stage of the process and the type of stone (always based on its hardness).
On the other hand, gemstone polishing discs are made of different materials and are used with abrasives that must also be selected according to the hardness of the gemstone.
Therefore, in this guide, you'll find:
Let's start with the first step, where you'll learn which discs I use to roughen gemstones.
Diamond laps for grinding gemstones
There are 60, 80, 100, 180, 260, 320, 360, 400, and 600 grit diamond discs on the market that can be used to grind gemstones.
However, I typically use diamond discs with 320, 360, 400, and 600 grit: the 320, 360, or 400 grit discs for grinding corundum (ruby and sapphire) and the 600 grit disc for other gemstones.
The reason I avoid using other discs is quite simple: when using a 60-grit disc, the stone is visibly scratched. This means I have to use other discs to smooth the surface.
To summarize, in the following table you can find the discs I use to roughen gemstones and some ideas of sites or platforms where you can buy them:
The roughing process is carried out exclusively with water, and to make it more efficient and sustainable, I suggest installing a drip system on your faceting machine that allows you to recycle the water.
Now, learn about the discs I use in the next phase of gem cutting.
Diamond faceting laps
For faceting gemstones, you can use 1200, 2000, and 3000 grit diamond laps. The one I use most often is the 1200 grit, although it all depends on the gemstone and the desired result.
In my experience, the 1200 grit diamond lap is useful for faceting most gemstones, while the 2000 grit lap may be more appropriate for faceting opals, sphalerites, and other soft gemstones.
Below are some suggestions on uses and the sites or platforms where you can purchase these materials:
Just like in the roughing process, in the gemstone faceting phase you only need to use water along with these diamond discs.
The importance of using an aluminum base when roughing and faceting gemstones
Gemstone roughing and faceting laps typically have a diameter of 15 to 20 cm and a center hole ranging from 12 to 13 mm, depending on the supplier. The size you choose depends on your faceting machine.
The thickness of the lap can also vary, and here's an important tip: since this is a thin lap, you may need to use an aluminum disc as a base.
This means you need to install an aluminum disc as a base and place the diamond roughing or faceting disc on it.
These discs (aluminum bases) can be found quite easily and are also available on platforms such as Amazon:
Finally, let's move on to the last step, where you'll find out which discs and abrasives I use to polish gemstones (yes, at this stage it's necessary to apply abrasives to the disc).
Discs and abrasives for polishing gemstones
To polish gemstones, I use a Tin disc, a Copper disc, and a felt disc. Of course, there are other materials on the market, but these are the three I use every day.
Tin disc for polishing gemstones
The Tin disc polishes almost all types of gemstones and works quite well with cerium oxide. Diamond powder can also give good results, especially when it comes to corundums (ruby and sapphire).
Copper disc for polishing corundums
The Copper disc is specifically designed for polishing corundums and, due to the hardness of these stones, should be used with diamond powder.
Felt disc for polishing cabochons
The felt disc polishes cabochon-cut stones and can be used on both faceting and cabochon machines. The abrasive I usually use in this case is Cerium oxide.
Below are some examples, with suggested platforms where you can purchase them:
There are also ceramic discs, leather discs, and even phenolic discs specifically for polishing opals that work with cerium oxide.
The important thing is to follow the manufacturer's specifications, use the appropriate amount of water or abrasives, and experiment until you find the combination that gives you the desired results.
