8 Easy Steps to Cut A Diamond

Are you a lapidary beginner looking to cut diamonds at home? Such a project is not impossible, but it requires specialized knowledge, craftsmanship, and equipment. You will also need to practice a lot before you can master the art of diamond cutting.

This article with show you how to cut a diamond using a faceting machine. Aside from sourcing the right equipment, you will also need to set aside at least 5 hours to cut and polish a diamond from its rough form to its finished state. Each diamond shape has its own cutting technique. Here, I will show you how to cut a brilliant round diamond.

You will need:

  • Faceting machine
  • Water
  • Various faceting laps
  • Flat working surface

Step by Step Guides on How To Cut A Diamond

Step 1: Map out the angles

Map out the angles

Before cutting a diamond, thorough planning is required. A diamond with an excellent cut has greater economic value.

Planning entails studying and mapping out the diamond’s angles and orientation to determine the best way to cut the stone. In addition to aiming for a perfect cut, you also want to minimize waste and make the best use of the stone.

This first step enables you to identify the rough’s tetrahedral plane and appropriate faceting angles. I recommend watching this helpful video to learn more about planning a rough diamond for the perfect cut.

Step 2: Dop the diamond

Dop the diamond

The next step is dopping your selected rough diamond. Dopping is simply the process of securing the stone onto a dopping stick to cut the diamond.

First, you will need to prepare the stone to mount it on a suitable dop stick. To get started, place a coarse lap onto the master lap on the faceting machine.

Set the faceter to high speed. Hold the stone in between your thumb and index finger and bring it to the surface of the lap. Slightly press the stone against the coarse lap to cut that initial flat surface that will enable you to mount the stone onto the dopping stick.

Next, wipe both the stone’s flat surface and dop stick head using a cotton ball and a few drops of methylated spirit. Do this thoroughly to ensure that the stone adheres to the dop stick head.

Follow the instructions to prepare the epoxy. Once it is ready, drop a small amount on the dop stick, and then attach the dop to the stone’s flat surface. Allow the epoxy to cure for 1-2 hours for the best outcome.

Pro Tip: Be sure to turn on the machine’s tap to allow water to flow and lubricate the spinning lap.

Step 3: Round the Stone For Girdling

Round the Stone For Girdling

Girdling is the process of forming the stone’s girdle. To do this, you first have to set the stone on the quill to lower the stone onto the grinding lap gradually.

To get started, set the machine’s index wheel on freewheel and the protractor to 90 degrees. Secure the coarse lap firmly on the master lap. Learn about how a faceting machine works.

Next, insert the dop stick with the stone into the quill and tighten the chuck if necessary. Loosen the coarse height adjusting wheel and raise the swarf tray. Then lower the head assembly such that the stone touches the edge of the coarse lap. Tighten the coarse adjusting wheel to secure the head assembly in place.

Now that you have the assembly set up, the next step is rounding the stone. To do this, use the micro height adjuster to lift the stone off the spinning lap. Then, set the machine at the highest speed and turn on the tap to medium flow.

Now, gradually lower the head assembly using the micro height adjuster until the stone touches the lap and produces a grinding sound.

Rotate the head assembly counterclockwise. Continue grinding until you hear the grinding sound change. This sound lets you know that you are getting closer to the maximum cutting depth set on the index wheel and protractor.

Step 4: Check Your Progress

Check Your Progress

Lift the stone off the lap and look at what’s happening. You’ll notice some parts of the stone have been ground but not others. Still, at this point, you should see some rounding effect.

Continue lowering the dop and grinding until the stone begins to look reasonably round. Always stop to examine your work until you feel comfortable with what you’re doing.

Pro Tip: Use your Vernier clip to check if your stone is out of round. It is important to get your stone as close to perfectly round as possible. Even the smallest variations can cause costly facet size mistakes.

Step 5: Cut the Pavilion Main Facets

Cut the Pavilion Main Facets

Set the coarse lap on the machine and adjust the speed to medium. Be sure to turn on the water for lubrication; the entire lap should be completely wet.

We are cutting a brilliant round diamond, which typically has eight pavilion facets. You will set the protractor at a 42-degree angle and the index at 96 degrees to cut the first facet. Set the index at 12, 24,36,48,60, and 72 to cut the subsequent pavilion facets.

After you are satisfied with the outcome of the first pavilion facet cut, move on to the next facet. Cut this subsequent facet at the next index setting, which is 48 degrees. Continue with this procedure until all the facets are cut at the set angle.

Remember to check your stone as you facet. Ensure that the facets do not meet at the center, as this means that you have cut the stone too deep without leaving space for cause correction.

Step 6: Pre-Polish the Pavilion And Girdle

Pre-Polish the Pavilion And Girdle

Now that you have cut the girdle and pavilion, it is time to polish up the diamond’s rough surface to remove dust and other contaminants. Use a damp cloth to clean the gem and the other parts of the machine.

Replace the coarse lap with the pre-polish lap. Start by pre-polishing the girdle. With the protractor still set at 90, adjust the index to 2. This low height allows you to only lightly polish the stone without removing too much material from it.

Move the stone back and forth, taking very light half sweeps across the lap. After the first sweep, check the stone. A well pre-polished girdle should be smooth and without any visible inclusions. If necessary, swipe the stone again across the lap to achieve a smooth surface.

Next, pre-polish the main pavilion facets. Adjust the protractor to 42 degrees and the index to 96. The diamond should only barely touch the lap. Pre-polish the facets as you did the girdle.

Finally, after pre-polishing the facets and girdle, replace the pre-polishing lap with a polishing lap. Follow the same procedure to polish the facets and girdle to achieve a perfectly smooth surface.

Step 7: Cut the Pavilion Break Facets

Cut the Pavilion Break Facets

The break facets are smaller than the main facets, so you want to be very gentle when cutting them.

Install a pre-polish lap on your machine and set the protractor to 43.7 and index to 2. The diamond should only barely touch the lap. Gently cut the first break facet at index 2 and the next one at index 10. Because break facets are small, make half instead of full swipes across the lap. A few swipes are enough to cut these small facets.

Polish the break facets before moving on to cut the main crown facets. Adjust the index to 2, ensuring that the stone only touches the lap. Swipe the stone halfway across the lap once or twice, then lift and check for smoothness. Lower and polish the stone again for an additional two to three seconds to achieve a smooth surface.

Step 8: Cut the Crown

The process of cutting the crown is similar to cutting the pavilion. But, you first need to turn the diamond over so that the crown faces outward. Use your faceting machine’s transfer tool to dop the diamond on the other side accurately.

After installing the new dop, set the protractor at 90 degrees and the index at 2. Lower the dop until the girdle facet lays flat on the lap. Then, tighten the dop, readjust the index to 96, and inspect the stone. The tips of the main facet should be well aligned, an indication that the dop is oriented.

Now that the dop is set, it is time to cut the crown. Install the course lap and set the protractor to 35 degrees and the index to 96. Use the same procedure to cut the pavilion facets to cut this first crown facet and subsequent crown facets. After cutting all the facets, pre-polish and polish the crown using the appropriate laps.

That’s it! You have now cut your diamond. Below are some extra tips to help make the diamond cutting process more efficient.

Extended Tips

  • Before attempting to cut a stone, inspect it for crevices. The presence of cuts and inclusions in a rough diamond can make the cutting process problematic.
  • Apply gentle pressure to avoid over-cutting the stone. Many lapidary hobbyists make the mistake of using the same lap to cut different facets, pre-polish and polish. For a perfectly cut diamond and to minimize wastage, change the laps accordingly.
  • Hand-control is among the most challenging aspects of the faceting process. You might set your machine accurately but still end up over-cutting, under-cutting, or causing other errors. To minimize these errors, be sure to check your progress after every few swipes on the lap.

Summary

The art of cutting diamonds requires a great deal of patience and practice. Everyone faces challenges when starting, but with time, you will cut your diamonds to perfection. Keep your hand pressure light and listen out for the faceting sounds to minimize errors that could throw off your diamond cutting process.

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