What Are Diamond-tipped Cutting Tools Made Out Of?

Ever wondered what exactly a “diamond-tipped” cutting tool is made of from its cutting edge to its core?

Diamond-tipped cutting tools are advanced composite instruments. Their cutting edge is made from specific grades of synthetic, industrial diamond—not natural gems. This diamond layer is bonded to a tough tungsten carbide substrate, which is then typically attached to a main body made of high-strength tool steel.

What Kind of Diamond Is Actually Used in These Tools?

When you hear “diamond-tipped tool,” does it mean a tiny piece of a brilliant gemstone is attached to the end?

The diamonds used in cutting tools are almost exclusively man-made, engineered materials, not natural gemstones. These synthetic diamonds fall into three main categories: Polycrystalline Diamond (PCD), which is a tough composite; Monocrystalline Diamond (MCD), a single pure crystal for ultra-fine finishes; and Chemical Vapor Deposition (CVD) Diamond, a highly pure diamond coating.

Polycrystalline Diamond (PCD): The Industry Workhorse

Imagine taking thousands of microscopic synthetic diamond grains and fusing them together with a metal binder (typically cobalt) under immense heat and pressure. The result is Polycrystalline Diamond, or PCD¹. It isn’t a single, clear crystal, but rather a solid, composite mass of interlocked diamond particles.

This structure is its greatest strength. Because the crystals are randomly oriented, PCD doesn’t have a weak direction or a natural cleavage plane. It wears uniformly and predictably, no matter the direction of the cut. Think of it like a block of high-strength concrete aggregate versus a single large stone; the aggregate is tough and resists chipping from any angle.

Consequently, PCD is exceptionally tough and versatile, making it the go-to material for high-volume machining of non-ferrous and highly abrasive materials.

• Industry Case Study: In the automotive industry, manufacturers use PCD-tipped milling cutters for machining aluminum alloy engine blocks and cylinder heads. A typical carbide tool might wear out after machining a few hundred parts, leading to frequent downtime for tool changes. In contrast, a single PCD tool can often machine tens of thousands of the same parts, drastically increasing production efficiency and ensuring consistent quality over long runs.
• Application Focus: It excels at cutting through materials like:
  • High-silicon Aluminum
  • Copper and Brass
  • Carbon Fiber Reinforced Polymer (CFRP)
  • Wood composites like MDF and particleboard

It is important to note that PCD is available in various diamond grain sizes, measured in microns. The specific grain size and diamond concentration can significantly affect the tool’s performance, balancing edge sharpness against abrasion resistance. Therefore, you should always consult your tool supplier to select the optimal PCD grade for your specific application and material.

Monocrystalline Diamond (MCD): For Ultra-Precision Finishes

Unlike the composite nature of PCD, Monocrystalline Diamond (MCD)² is a single, continuous synthetic diamond crystal. It has no grain boundaries and no binder material—it is pure, uninterrupted diamond. This purity allows it to be sharpened to an incredibly fine and precise cutting edge, far sharper than what is possible with PCD.

The primary goal of using MCD is not to remove large amounts of material, but to achieve an extraordinary surface finish, often described as a “mirror finish.” However, this perfection comes with a trade-off. As a single crystal, MCD has natural cleavage planes, making it more brittle and susceptible to chipping if subjected to shock, vibration, or interrupted cuts.

• Industry Example: MCD tools are critical in manufacturing high-technology components. For instance, they are used to machine the aluminum platters for computer hard drives. These platters must be incredibly smooth to allow the read/write head to float just nanometers above the surface. Only an MCD tool can produce the required mirror-like, defect-free finish. Similarly, it’s used for creating optical-quality surfaces on acrylic lenses and metal mirrors for scientific instruments.

Chemical Vapor Deposition (CVD) Diamond: The High-Tech Coating

What if you could take a tough, conventional tool and give it a pure diamond skin? That is the essence of Chemical Vapor Deposition (CVD) Diamond. This process involves “growing” a thin but highly durable film of pure diamond directly onto a substrate, which is typically tungsten carbide.

In a vacuum chamber, gases like methane are broken down, allowing carbon atoms to settle and form a pure, binder-free diamond film on the tool’s surface. This creates a cutting edge that combines the extreme hardness and low friction of pure diamond with the underlying toughness of the carbide tool body.

Because it lacks the metallic binder found in PCD, CVD diamond is chemically inert and extremely resistant to abrasive wear, making it uniquely suited for machining very aggressive materials.

• Application Focus: CVD diamond tools have proven invaluable for machining highly abrasive non-metallic materials where the binder in PCD could be preferentially worn away. A prime example is the machining of graphite electrodes used in Electrical Discharge Machining (EDM). Graphite is notoriously abrasive and quickly wears down even carbide tools. A CVD diamond coating, however, provides a protective, ultra-hard layer that can extend the tool’s life by a factor of 10 to 20 times in this application, ensuring the complex electrode shape remains accurate.

What Is the Rest of the Tool Body Made From?

Now that we know about the diamond cutting edge, what about the rest of the tool? Since that diamond layer is often incredibly thin, what gives the tool its actual shape and strength?

The body of a diamond tool is a strategic combination of materials. A super-tough tungsten carbide substrate typically sits directly behind the diamond layer to provide critical support, while the main body and shank of the tool are usually made from high-strength tool steel for cost-effectiveness and machinability. These parts are then joined using specialized high-temperature processes.

Tungsten Carbide: The Tough Substrate Supporting the Diamond Layer

Diamond is the hardest material known, but it’s also brittle—much like glass. On its own, a thin layer of diamond would shatter under the intense forces of cutting. This is where tungsten carbide comes in. It acts as the ultimate support system.

Think of it like the steel rebar inside a concrete pillar. The concrete provides a hard, wear-resistant surface, but the rebar inside gives it the strength and flexibility to keep from cracking under pressure. Tungsten carbide serves this exact purpose for the diamond layer. It is incredibly hard itself, yet it possesses far greater toughness (resistance to chipping and impact) than diamond³.

This combination of properties makes it the perfect material to serve as a substrate, or the immediate backing layer for the diamond cutting edge. During manufacturing, the PCD layer is often sintered directly onto a thicker tungsten carbide base, creating a single, inseparable composite tip. This tip has the hardness of diamond on the surface and the toughness of carbide right behind it.

• Industry Example: Look at the small, indexable inserts used in CNC milling or turning. The tiny, sharp cutting point is diamond, but the bulk of that replaceable tip—the part that gets clamped into the tool holder—is solid tungsten carbide. This design allows the brittle diamond edge to withstand immense cutting forces because it is fully supported by its tough carbide partner.

Tool Steel: Forming the Main Body and Shank

So if tungsten carbide is the direct support, what is the rest of the tool made of? For most tools, the answer is high-quality tool steel.

Why not make the entire tool out of tungsten carbide? Two main reasons: cost and machinability.

1. Cost: Tungsten carbide is significantly more expensive than steel.
2. Machinability: Steel is much easier to machine into the complex shapes needed for tool bodies, like the long shank of a drill bit or the large disc of a circular saw blade.

Therefore, manufacturers use a “best of both worlds” approach. They use the premium PCD/carbide composite only where it’s needed—at the cutting point. The rest of the tool’s non-cutting structure, like the body and shank, is made from strong and reliable tool steel.

• Analogy: Consider a professional socket wrench. The small socket that grips the bolt is made from an extremely strong chrome-vanadium steel alloy to prevent it from stripping. The long handle you turn, however, is made from a different, less expensive steel. It would be needlessly expensive to make the entire handle from the same material as the socket. Diamond tools follow the same logic.

How They Are Joined: A Look at Sintering and Brazing

Creating a finished diamond tool involves two distinct joining processes that bring these different materials together.

Sintering – Creating the Cutting Tip

Sintering⁴ is a high-tech manufacturing process that uses intense heat and pressure to fuse powdered materials together without melting them. This is how the diamond (PCD) layer and its tungsten carbide substrate are bonded into a single solid piece. The powdered materials are pressed together in a mold and heated until their atoms bond, forming an incredibly strong and seamless connection.

Brazing – Attaching the Tip to the Body

Once the PCD/carbide tip has been created through sintering, it must be attached to the larger steel tool body. This is done through brazing⁵, a high-temperature joining process.

• The Process: An alloy with a lower melting point is placed between the carbide tip and the steel body.
• The Heat: The entire assembly is heated until the brazing alloy melts, flows into the tiny gaps between the parts, and then solidifies upon cooling.
• The Result: This creates a powerful metallurgical bond, much like high-strength soldering, that permanently welds the cutting tip onto the tool body.

So, when you see a tool like a PCD face mill or a boring bar, you are looking at a product of this two-step process: one or more individually sintered PCD/carbide tips that have each been expertly brazed onto the precision-machined steel tool body.

Are These the Same Diamonds Used in Jewelry?

Considering that these tools use genuine diamond, why can you buy a diamond-tipped saw blade for a fraction of the cost of a diamond engagement ring?

No, the diamonds used in cutting tools and jewelry are fundamentally different in both origin and purpose. Industrial diamonds are synthetic materials engineered for physical properties like hardness and are typically produced as imperfect crystals or powders. In contrast, gem-grade diamonds are valued for their visual beauty—their clarity, color, and natural rarity.

Industrial-Grade vs. Gem-Grade Diamonds

The core difference lies in what each type of diamond is designed to do. One is a high-performance industrial material; the other is a precious decorative object. Their paths from creation to application could not be more different.

• Industrial Diamonds are almost entirely synthetic, created in labs using processes that replicate the high-pressure, high-temperature (HPHT) conditions deep within the Earth. The goal is to produce diamond material with optimal functional properties, quickly and in large volumes.
• Gem-Grade Diamonds are traditionally valued for being natural and mined, with their rarity being a key part of their value. While lab-grown gems are now common, their creation process is much slower and more controlled than that for industrial diamonds, aiming for visual perfection.

Think of it like quartz. A handful of common beach sand is made of quartz crystals, perfect for making concrete. This is the industrial-grade equivalent. A large, perfectly clear, flawlessly cut quartz crystal displayed in a museum is the gem-grade equivalent. Both are the same chemical compound, but their form, function, and value are worlds apart.

Function Over Flawless Appearance

When an engineer selects a diamond for a cutting tool, the checklist of requirements is completely different from a jeweler’s.

What do engineers look for?

1. Extreme Hardness: The defining characteristic, allowing it to cut nearly any other material.
2. Abrasion Resistance: The ability to withstand being worn down while machining abrasive materials like composites or concrete.
3. Thermal Conductivity: This is a critical, often overlooked property. Diamond is one of the best thermal conductors on Earth, five times better than copper. It rapidly pulls heat away from the cutting edge, preventing both the tool and the workpiece from overheating and getting damaged.

What is completely irrelevant for an industrial diamond?

• Color: A yellow or brown tint from nitrogen impurities doesn’t affect hardness.
• Clarity: Internal flaws, cracks, or inclusions are unimportant. In PCD, a structure full of grain boundaries is actually a strength.
• Size: A bonded mass of tiny, sharp crystals is often tougher and more effective than one large, single point.

Industry Case Study: When machining carbon fiber reinforced polymer (CFRP) for an aircraft fuselage, the material is extremely abrasive, like cutting through fine sandpaper. A tool with a large, gem-quality diamond would quickly develop a worn flat spot. In contrast, a PCD tool exposes thousands of microscopic, razor-sharp cutting edges. As some crystals wear down or break away, new sharp edges underneath are exposed, allowing the tool to maintain its cutting ability for much longer. The tool’s “ugly,” composite structure is precisely what makes it functionally superior for the job.

Why the Cost is Drastically Different

The enormous price gap between a diamond drill bit and a diamond necklace comes down to simple economics: supply and demand, driven by the differences we’ve just discussed.

Mass Production vs. Natural Rarity

The global output of synthetic industrial diamond is staggering, estimated in the billions of carats per year. It is a mass-produced industrial commodity, manufactured in factories around the world. The supply is vast, consistent, and designed to meet industrial needs.

In sharp contrast, the supply of natural gem-quality diamonds is limited to what can be discovered and mined from the Earth. This inherent rarity is the primary driver of their high value. Even the market for lab-grown gems, while growing, operates on a much smaller scale and with a focus on slow, perfect crystal growth that is far more costly than industrial production.

The Goal of Manufacturing

The process to create industrial diamond powder is optimized for one thing: high-volume output at the lowest possible cost.

The process to grow a single, large, flawless gem in a lab is optimized for perfection. It requires weeks of stable, energy-intensive operation to produce a single stone, making the cost per carat exponentially higher. You are paying for the time, control, and energy needed to achieve beauty, not just the raw material itself.

Conclusion

In summary, a diamond-tipped cutting tool is far more than just a piece of diamond. It is a highly engineered system where each material is chosen for a specific purpose. The process starts with a carefully selected grade of synthetic diamond—like PCD, MCD, or CVD—to form the cutting edge. This diamond layer is then critically supported by a tough tungsten carbide substrate, which provides the strength to withstand immense cutting forces. Finally, this composite tip is joined to a cost-effective and durable tool steel body. This intelligent combination of materials creates a tool that is immensely powerful and durable, while the use of industrial-grade, not gem-grade, diamond makes it an economically viable solution for modern manufacturing.

References

1. Polycrystalline Diamond, or PCD¹ – An in-depth guide from ZYDiamondTools explaining the properties and applications of PCD tools.
2. Monocrystalline Diamond (MCD)² – ZYDiamondTools’ technical guide to MCD tools, their uses, and their benefits for achieving mirror finishes.
3. toughness (resistance to chipping and impact) than diamond³ – A ZYDiamondTools article directly comparing the characteristics of PCD and traditional carbide tools.
4. Sintering⁴ – Wikipedia’s detailed explanation of the sintering process, covering its principles and applications in manufacturing.
5. brazing⁵ – The Wikipedia page for brazing, explaining the process, materials, and its advantages as a joining technique.