Cutting ToolsTool materials

ISO 513 — the P M K N S H classification

How ISO 513 sorts carbide, ceramic, diamond and cBN cutting materials by application. The six main groups and their colours, what the numbers 01 to 50 mean, the letter symbols such as HW, HC and CA, and how to read a designation like HC-P10.

LiveUpdated 11 October 20265 min read

ISO 513 main groups and their colours

Main groups: P, M, K, N, S, H: 6
The widest range of application groups: P01–P50
Current edition, the fourth; confirmed in 2018: 2012

Insert boxes and catalogues mark grades with a letter and a number such as P25 or K10, often with a coloured stripe. They come from ISO 513, the standard that tells you which work materials a cutting material is meant for and whether it leans toward wear resistance or toughness. It is the first filter when choosing a grade.

What the standard does — and does not do

ISO 513 covers hard cutting materials for tools with defined cutting edges: hardmetals (cemented carbides), cermets, ceramics, diamond and cubic boron nitride. It classifies them by application, not by composition or measured properties. Its introduction states that it was not possible, at the time of publication, to standardise hard cutting materials by their characteristics, so the standard limits itself to their application. The standard defines no test, so where a particular grade sits on these scales comes from its maker’s catalogue.

The current version is ISO 513:2012, the fourth edition. ISO last reviewed and confirmed it in 2018.

Six main groups

The main groups are named after the work material, each with an identification colour.

GroupWorkpiece materialApplication groups

P blueSteel: all steels and cast steels except austenitic stainlessP01 … P50

M yellowStainless steel: austenitic and austenitic-ferritic (duplex) steel and cast steelM01 … M40

K redCast iron: grey, spheroidal-graphite and malleable cast ironK01 … K40

N greenNon-ferrous metals: aluminium and others; non-metallic materialsN01 … N30

S brownSuperalloys and titanium: heat-resistant Fe, Ni and Co based alloys; titanium alloysS01 … S30

H greyHard materials: hardened steel, hardened cast iron, chilled cast ironH01 … H30

01: wear resistance, higher speed50: toughness, higher feed

ISO 513:2012 main groups, identification colours and the span of their application groups. Only P runs to 50; M and K stop at 40; N, S and H stop at 30.

Group	Colour	Work materials
P	blue	Steel: all kinds of steel and cast steel, except stainless steel with an austenitic structure
M	yellow	Stainless steel: austenitic and austenitic-ferritic (duplex) steel and cast steel
K	red	Cast iron: grey, spheroidal-graphite and malleable cast iron
N	green	Non-ferrous metals: aluminium and other non-ferrous metals; non-metallic materials
S	brown	Superalloys and titanium: heat-resistant alloys based on iron, nickel and cobalt; titanium and titanium alloys
H	grey	Hard materials: hardened steel, hardened cast iron, chilled cast iron

What the numbers mean

Within each main group, application groups are numbered 01, 05, 10, 15 and so on: P01 to P50, M01 to M40, K01 to K40, N01 to N30, S01 to S30 and H01 to H30.

Low numbers mean a more wear-resistant cutting material, for higher cutting speeds.
High numbers mean a tougher cutting material, for higher feeds.

The footnotes to the standard’s table say exactly this: increasing speed calls for increasing wear resistance, increasing feed for increasing toughness. A K10 grade is therefore meant for cast iron at high speed and light feed; a P40 grade for steel at lower speed and heavier feed, where toughness matters more than wear resistance.

Letter symbols for the cutting material

A second set of letters names the type of cutting material.

Symbol	Cutting material
HW	Uncoated hardmetal, mainly tungsten carbide (WC), grain size ≥ 1 µm
HF	Uncoated hardmetal, mainly WC, grain size < 1 µm
HT	Uncoated hardmetal, mainly titanium carbide or nitride (TiC, TiN or both); also called cermet
HC	Hardmetals as above, but coated
CA	Oxide ceramic, mainly aluminium oxide (Al₂O₃)
CR	Oxide ceramic, Al₂O₃, reinforced
CM	Mixed ceramic, Al₂O₃ with components other than oxides
CN	Silicon nitride ceramic (Si₃N₄)
CC	Ceramics as above, but coated
DM	Monocrystalline diamond
DD	Polycrystalline diamond without binder
DP	Polycrystalline diamond with binder
BL	Cubic boron nitride with low cBN content
BH	Cubic boron nitride with high cBN content
BC	Cubic boron nitride as above, but coated

Reading a full designation

The full designation is the material symbol, a dash, and the application group. The standard’s own examples:

HW-P10: uncoated carbide, WC grain ≥ 1 µm, for steel, toward the wear-resistant end.
HC-K20: coated carbide for cast iron, in the middle of the K range.
CA-K10: aluminium oxide ceramic for cast iron, toward the wear-resistant end.

HCCutting materialCoated hardmetal

KMain groupCast iron

20Application groupin the middle of K01–K40

K01K05K10K15K20K25K30K35K40

← wear resistance, higher speedtoughness, higher feed →

The three example designations taken apart. The scale shows where the application group sits in its main group's range. Pick an example to compare.

Using it in practice

Find the main group from the work material. An austenitic stainless steel is M, not P, even though it is steel.
Choose the position on the scale from the operation. High speed and light feed point to low numbers; heavy feed and a need for toughness point to high numbers.
Pick a grade whose published range covers that position, then confirm it with the maker’s own cutting data.

To decode the rest of an insert’s designation — shape, clearance, tolerance, size — use the insert code decoder.

Sources (7)

Every value and quotation on this page comes from the documents below.