Insights based on Element Six’s Precision Machining Handbook
Choosing the right Polycrystalline Diamond (PCD) grade is not simply a matter of selecting the “hardest” option available. In real-world machining environments, PCD grade selection directly influences surface finish, tool life, edge stability, and overall production efficiency.
As outlined in Element Six’s Precision Machining: Giving Toolmakers a Competitive Edge handbook (covering PCD, PCBN, CVD diamond and single crystal diamond solutions), different PCD grades are engineered for very different outcomes. Grain size, microstructure, and processing behaviour all affect how a tool performs in application and how it can be manufactured.
This article breaks down key PCD grades and characteristics highlighted in the Element Six handbook, and explores how manufacturers and toolmakers can think more strategically about grade selection.
Why PCD Grade Selection Matters
PCD tooling is widely used for high-performance machining, particularly in applications requiring excellent wear resistance, reliable edge retention, and consistent cutting performance.
However, not all PCD behaves the same way.
Element Six highlights that PCD grade performance is strongly influenced by factors such as grain size and microstructure. These differences determine how the material responds to cutting forces, abrasion, heat, and impact, and also influence how easily the tool can be processed during manufacturing.
Selecting the wrong grade can result in:
- premature wear
- edge chipping
- inconsistent surface finish
- reduced productivity due to tool changes
- reduced process stability and repeatability
In high-performance machining environments, these are not minor issues. They directly affect production planning, part quality, and profitability.
Grain Size: A Key Indicator of Performance
One of the most useful ways to understand PCD grade behaviour is through grain size.
In general:
- Finer grain sizes support sharper edges and higher-quality surface finishes.
- Coarser grain sizes provide stronger wear resistance in abrasive machining conditions.
Element Six’s grade table illustrates this clearly, showing how PCD grades are engineered to meet specific machining demands, rather than being interchangeable materials.
CMX850: Ultra-Fine Grain for Sharpness and Mirror Finishes
In the Element Six handbook, CMX850 is positioned as ideal for milling and rough cutting of aluminium alloys where extreme chip resistance is required, and can also be used for machining titanium.
Its defining characteristic is its sub-micron grain size, which supports extreme edge sharpness and strong edge retention. Element Six notes that CMX850’s ultra-fine grain structure is suitable for applications where mirror finishes are required.
This makes it particularly valuable where surface finish requirements are high and where edge stability is essential.
Best suited for:
- high surface finish machining
- aluminium alloy applications requiring sharp edges
- precision environments requiring strong edge retention
CTX002: A Grade Designed for Complex Tool Manufacturing
Element Six describes CTX002 as ideal for profile routers and thread cutting tools, with potential use in wear part applications.
With an average grain size of 2 μm, CTX002 also includes increased cobalt content to support ease of processing. This is a critical point: in many applications, grade selection must account not only for performance in machining, but also for how efficiently and reliably the tool itself can be manufactured.
Element Six positions CTX002 as particularly suitable for complex tools where intensive processing is required.
Best suited for:
- complex tool geometries
- profile routers
- thread cutting tools
- wear part applications
CTB004: Fine Grain Balance Between Finish and Wear Resistance
According to Element Six, CTB004 is ideal for cutting aluminium alloys where high surface finish is required, alongside higher wear resistance.
Its average grain size of 4 μm provides a fine grain structure that Element Six notes offers an optimum balance between tool performance and resistance to abrasions and chips.
This makes CTB004 a strong option where manufacturers want high surface quality without sacrificing durability.
Best suited for:
- aluminium alloys requiring improved finish
- stable machining where wear resistance remains important
- applications requiring a balance of quality and tool life
CTB010: A Workhorse Grade for Roughing and Finishing
Element Six describes CTB010 as an ideal grade for roughing and finishing performed with a single tool. It is also highly recommended for low to medium silicon content aluminium alloys.
With an average grain size of 10 μm, CTB010 is positioned as a practical, production-focused grade. Element Six refers to it as a workhorse PCD grade, suitable for applications where a strong balance of toughness and wear resistance is required.
This kind of grade is valuable in manufacturing environments where consistency and reliability matter as much as performance.
Best suited for:
- low to medium silicon aluminium alloys
- roughing and finishing with a single tool
- general production environments requiring predictable performance
CTH025: Coarse Grain for Abrasive Machining Conditions
Element Six notes that CTH025 is suitable for machining high silicon aluminium alloys, metal matrix composites (MMC), tungsten carbides, and ceramics.
With an average grain size of 25 μm, CTH025 is positioned as a grade that offers optimum wear resistance for abrasive machining conditions.
This is particularly important because materials such as MMCs and high silicon aluminium alloys can cause rapid tool degradation. In these environments, grade selection becomes critical to maintaining tool life and process efficiency.
Best suited for:
- high silicon aluminium alloys
- MMC machining
- tungsten carbides and ceramics
- abrasive machining environments requiring maximum wear resistance
CTM302: Multi-Modal PCD for High-Demand Applications
One of the most technically interesting grades highlighted by Element Six is CTM302.
It is described as a multi-modal PCD with grain size ranging from 2 μm to 30 μm, delivering excellent wear resistance, edge strength, and quality, alongside outstanding abrasion resistance and good thermal stability.
Element Six lists application areas including MMC, high silicon aluminium alloys, high strength cast irons, and bi-metal applications.
This grade is clearly positioned for environments where multiple performance characteristics are required simultaneously, and where thermal and mechanical stability play a major role in achieving consistent machining results.
Best suited for:
- MMC machining
- high silicon aluminium alloys
- high strength cast irons
- bi-metal applications requiring edge strength and stability
A Practical Framework for Grade Selection
The Element Six handbook provides a useful reminder that PCD selection should be aligned with manufacturing priorities, not assumptions.
A simplified selection framework might look like this:
- Need mirror finishes and sharp edges? Consider ultra-fine grain grades such as CMX850.
- Need complex tool manufacturing and intensive processing? CTX002 may be a suitable fit.
- Need balance between finish and wear resistance? CTB004 offers a mid-range solution.
- Need a reliable production-grade option? CTB010 is positioned as a strong workhorse grade.
- Machining abrasive materials like MMC or high silicon alloys? CTH025 is designed for high abrasion environments.
- Need broad capability across challenging materials? CTM302 offers a multi-modal structure with thermal stability.
Conclusion: PCD Is Not One Material
As Element Six’s Precision Machining handbook makes clear, PCD grade selection is not a single-variable decision. Grain size and microstructure have direct consequences for surface finish, abrasion resistance, processing behaviour, and long-term tool performance.