How to Choose CNC Diamond Engraving Bit for Stone Carving Projects

  The CNC diamond engraving bit plays a crucial role in achieving precision, durability, and high-quality surface finishes. Choosing the right CNC milling bit ensures smoother engraving, longer tool life, and reduced risk of breakage. For professionals working with granite, marble, quartz, or other hard stones, understanding how to select the right CNC bits, router bits, and cylinder bits is essential for efficient operation.

Below are three key factors you should always consider before selecting your CNC diamond engraving tools.

1. Selecting the Right Shank Diameter

The shank diameter determines the bit’s overall strength and stability during stone engraving. Choosing a proper shank size helps maintain tool rigidity and prevents breakage under heavy load.

• For reliefs within 20mm depth, it is recommended to use an 8mm shank. This offers sufficient stability for shallow to medium-depth carvings.

• For deep reliefs over 20mm, a 10mm shank provides greater structural strength and stability, reducing vibration and the risk of snapping.

• If your CNC engraving machine is powerful and supports high-speed cutting, a 12mm shank can be used to ensure the bit maintains accuracy and balance even at high spindle speeds.

A strong and well-matched shank helps your CNC bits maintain cutting precision and withstand the demanding nature of stone carving.

2. Choosing the Proper Tip Size

The tip size of the engraving bit directly affects both carving precision and tool durability. In stone work, where materials are extremely hard, the balance between detail and endurance is especially important.

• As long as engraving accuracy allows, choose a larger tip to extend the bit’s lifespan. For example, if a 6mm tip meets your precision requirements, avoid using smaller 3mm or 4mm tips.

• Larger tip sizes offer better heat dissipation, more robust cutting edges, and longer service life under the stress of engraving stone.

• Smaller tip bits are only recommended for fine detailing or delicate patterns that require extra precision.

In short, for most relief carvings on stone, the largest possible tip size that satisfies precision needs will deliver the best overall performance.

3. Determining the Correct Cutting Length

The cutting length (also called flute length) should always be chosen based on the engraving depth and the flatness of the stone surface. An incorrect cutting length can cause friction between the shank and the stone, damaging both the tool and the material.

• For an engraving depth of 26mm, select a bit with a 30mm cutting length to keep a safe margin.

• For 15mm depth, a 20mm cutting length is sufficient.

• Always ensure there’s enough clearance so the bit’s shank doesn’t touch or grind against the stone surface.

Choosing a suitable cutting length helps maintain consistent cutting pressure, reduce vibration, and protect both the CNC diamond engraving bit and your CNC router.

4. Practical Tips for Stone Engraving

• Always use CNC diamond engraving bits designed specifically for stone materials such as granite, marble, or artificial stone.

• Inspect bits regularly and replace them once the diamond edge shows visible wear.

• Adjust the spindle speed and feed rate according to the bit size and stone hardness.

• Keep the working area clean and use adequate water cooling to prevent overheating.

Conclusion

Selecting the right CNC diamond engraving bit for stone carving is not just about tool size — it’s about achieving the perfect balance between precision, strength, and longevity. By paying attention to the shank diameter, tip size, and cutting length, you can ensure efficient performance and longer tool life in your stone engraving projects.

Whether you are working with granite, marble, or engineered stone, choosing the proper CNC bits, router bits, or cylinder bits will help you produce clean, detailed, and professional-quality carvings every time.