How to Use Diamond Discs for Faceting: From Coarse Grit to Polishing Perfection

Faceting gemstones is both an art and a science. Whether you are working with sapphire, quartz, topaz, or other gemstones, mastering the use of diamond discs is key to achieving a flawless finish. In this post, we’ll explore step by step how to go from coarse grits all the way to ultra-fine polishing using diamond paste, so your stones shine like professional gems.

Here’s a video explaining How to Use Diamond Discs for Faceting from my YouTube channel GottaPics

Understanding Diamond Discs and Grit Sizes

Diamond discs are the backbone of gemstone faceting. They come in various grit sizes, which determine how coarse or fine the cut will be. Here’s a quick overview:

• Coarse Grit (80–220): Removes material quickly, shapes the stone, and prepares it for finer grits.
• Medium Grit (400–600): Smooths out scratches from coarse discs and starts refining the facets.
• Fine Grit (1200–3000): Produces a near-polished surface, removing minor scratches and preparing for diamond paste.
• Ultra-Fine Grit & Diamond Paste (6000, 14000, 60000): Used for final polishing to achieve a mirror-like finish on hard stones like sapphire.

Knowing when to switch grits and how much pressure to apply is essential to prevent unwanted scratches or uneven surfaces.

Step 1: Shaping with Coarse Grit

Start with the coarsest grit disc, usually around 80. This stage is for shaping the stone and creating the initial facets.

Tips:

• Keep the stone moving to avoid gouges or flat spots.
• Use a consistent, gentle pressure. Hard pressing can break the stone, especially delicate sapphires.
• Frequently check the facets with a loupe to ensure symmetry.

Coarse grit is aggressive and removes material quickly, so it’s the foundation of your faceting work. Think of it as rough sculpting before fine detailing.

Step 2: Refining with Medium Grit

Once your facets are shaped, move to medium grit, typically around 400–600. This step is all about removing scratches left by the coarse disc and starting to refine the stone’s surface.

Scenario Tip:

• Hard stones like sapphire might need longer on medium grit because scratches from coarse discs are deeper.
• Softer stones, such as quartz, can move faster to the next grit.
• Always clean the stone and disc between grit changes to prevent cross-contamination. Even a tiny remaining coarse particle can ruin your fine polishing.

Step 3: Fine Polishing with High Grit Discs

After medium grit, switch to fine grit discs (1200–3000). This is where the stone starts to shine. Each pass removes the micro scratches from the previous stage, bringing the surface closer to a polished look.

Tips for Sapphire and Other Hard Stones:

• Sapphire is very hard, so fine grit might take longer than expected. Patience is key.
• Work systematically on each facet, ensuring you maintain the angles and symmetry.
• For multi-colored stones, observe how the light interacts with facets to detect scratches.

Step 4: Final Polish with Diamond Paste

For a true mirror finish, you’ll move to diamond paste, typically in stages: 6000, 14000, and finally 60000.

Step-by-step:

1. Apply 6000 grit paste on a soft felt or leather lap. Polish all facets evenly.
2. Move to 14000 grit paste for a higher shine. This stage removes the fine scratches left by 6000 grit.
3. Finish with 60000 grit paste, especially for sapphires or any gemstone where a flawless polish is desired.

Scenario Tips:

• Use light pressure to avoid rounding the facet edges.
• Keep the lap clean; any grit from previous stages can scratch your stone.
• For sapphires, always check under strong light to see if all micro-scratches are gone.

Common Challenges and How to Avoid Them

• Scratches from previous grit: Always clean both stone and disc before moving to finer grits.
• Uneven facets: Keep the stone moving consistently and maintain correct angles.
• Overheating: Hard stones like sapphire can crack if friction generates too much heat. Use water or lubricant when recommended.

Choosing the Right Disc for Different Stones

• Sapphire: Very hard—requires patience, fine grit discs, and high-quality diamond paste for mirror polish.
• Quartz or Topaz: Softer stones polish faster, but watch for chipping at edges.
• Multi-colored or delicate stones: Take extra care at coarse stages to prevent fractures.

Conclusion

Mastering diamond discs and the proper grit progression is essential for professional-quality faceting. From coarse shaping at 80 grit to ultra-fine polishing with 60000 grit diamond paste, every stage matters. Each stone has its personality, so learning to adapt the process to sapphire, quartz, or topaz ensures the best results.

If you want a visual demonstration of all these steps, check out my latest YouTube video embedded above. You’ll see exactly how I go from rough shaping to a flawless polished finish using diamond discs on my faceting machine.

Pro Tip: Keep a log of grit progression for each type of stone you work on. Over time, you’ll develop a workflow that saves time and produces consistently beautiful gems.