C2, C6 and K10 help describe where a cutting grade may be useful. They do not uniquely specify its cobalt percentage, grain size, hardness or processing recipe. Start with the application label, then compare the supplier's named grade and measured properties.
C-Grades and ISO Numbers Run in Different Directions
Within the traditional C1–C4 and C5–C8 families, lower C numbers generally favor tougher cutting conditions; higher numbers favor finishing. ISO application numbers run the other way: lower numbers generally favor wear resistance, while higher numbers cover tougher conditions. Ranges overlap. See page 2 of Kennametal's cutting-tool blank guide.
| Label | How to use it |
|---|---|
| C2 | A traditional class commonly associated with cast iron and non-ferrous machining; identify the supplier grade |
| C6 | A traditional steel-cutting class; check its operating range |
| K10 | A position within an ISO cutting application group; it is not a powder formulation |
These labels narrow a search. They do not make different suppliers’ grades interchangeable. Record the full manufacturer designation alongside the application class, then compare the properties and operating conditions relevant to your part.
Why C2 Does Not Mean One Composition
Two examples from page 1 of the same Kennametal guide demonstrate the variation:
| Named Kennametal grade | C-class | Cobalt, wt.% | Hardness, HRA |
|---|---|---|---|
| KFF05 | C2 | 5.5 | 92.2 |
| KFS64 | C2 | 10.0 | 91.8 |
These are manufacturer nominal values, not NOC specifications or acceptance limits. Kennametal recommends application assessment and field trials. The differing cobalt and hardness values show why C2 alone is insufficient to select a composition.
What ISO 513 Covers
ISO 513:2012 classifies hard cutting materials for machining by chip removal. Its scope includes carbide, ceramics, diamond and boron nitride. It explicitly excludes applications such as mining/percussion tools and wire-drawing dies. A cutting-tool application code therefore should not be treated as a complete specification for a wear part or mining button.
Substrate, Binder and Coating Still Matter
At a fixed binder content, finer WC grain generally increases hardness. At a fixed WC grain size, more binder generally increases toughness while increasing susceptibility to plastic deformation. A coated cutting grade combines its substrate and coating; the application label alone does not describe either completely. These relationships and their conditions are explained in Sandvik Coromant's cutting-tool material guide.
Use the manufacturer's full grade designation when comparing products. Do not infer a universal meaning for each digit of a proprietary code or assume that matching application labels guarantee matching performance.
Turning an Application Goal into a Powder Request
Give the powder supplier the intended part and operating conditions, alongside the reference grade. Ask the supplier to identify the proposed composition, particle-size measurement method and range, relevant impurity limits, and the properties that will be checked after processing.
For a finished component, agree on the test method and acceptance limits as part of the specification. For powder, agree on what the powder certificate reports. Keep those two sets of measurements distinct: a powder label cannot by itself certify the properties of a sintered and coated cutting tool.
The practical sequence is application → named candidate grade → agreed powder and processing requirements → tested component. The grade code is the beginning of that conversation.