Cutting materials: carbide, HSS, coatings and ISO 513
Why the yellow cast should not go into the blue part — the material groups that guide your tool choice
The right blade in the wrong material wears out in minutes; the right blade in the right material runs a whole series. The choice of cutting material is therefore not a detail but a decision that determines both quality runtime and economy. To make the choice systematic the tool industry has a common language: the type of cutting material any coating and a color code that matches the workpiece.
§From HSS to hard metal and beyond
High-speed steel (HSS) is tough and cheap and withstands shocks and interrupted cuts well — it is still used for drills taps and many mills. Carbide (sintered tungsten carbide) is harder and withstands far higher cutting speeds and heat but is more brittle. It is most often supplied as replaceable inserts so you can index the insert to a new edge instead of grinding. For the hardest and fastest tasks there are also cermet ceramic CBN and PCD (diamond) — each with its own application and price.
| Cutting material | Strength | Typical use |
|---|---|---|
| HSS | Tough cheap tolerates shock | Drill, tap, mill at low Vc |
| Carbide | Hard high Vc | Turning plates for turning and milling |
| Ceramic / CBN | Very hard, heat-resistant | Hardened steel high production |
| PCD (diamond) | Extremely hard. | Aluminum and non-ferrous abrasive metals |
§Coatings extend life
Most modern inserts are coated with a thin, hard layer that increases wear resistance and reduces friction. Titanium nitride (TiN) is the classic golden coating. Titanium aluminum nitride (TiAlN/AlTiN) tolerates more heat and is used where it goes fast or dry because it forms a protective oxide layer at high temperatures. Coatings can reduce built-up edge (BUE) — the material that otherwise sticks to the cutter and ruins the surface. A coating does not make a wrong insert right but it makes the right insert last longer.
§ISO 513: the colors that match the workpiece
To make it easy to choose parts, ISO 513 divides the workpiece materials into six main groups, each with its own colour, and tool suppliers colour-code their cutting edges accordingly. The groups are not just about what the material is, but about how it behaves when cut. A cutting edge designed for the tough, sticky group M (stainless steel) has a different geometry and coating than one for the short, hard-wearing group K (cast iron).
| Group | Colour | Materials |
|---|---|---|
| P | Blue | Steel (unalloyed, low and high-alloyed) |
| M | Yellow | Stainless steel (austenitic, duplex) |
| K | Red | Cast iron |
| N | Green | Non-ferrous metals: aluminium, copper, brass |
| S | Brown | Superalloys and Titanium |
| H | Grå | Hardened steel and hard materials |
- 01Choose cutting material based on item, cutting speed and whether the cut is interrupted
- 02Coating increases service life but does not replace correct blade selection
- 03Turning plates are reused by turning to a fresh egg — save on changes
- 04Color psychology and aesthetics.
“Hard blade soft head: know your material before you choose your tool.”