# ISO Cutting Tool Material Groups (P, M, K, N, S, H) Reference

> Source: https://netray.co/tools/cnc-cutting-tool-iso-material-group-reference
> Publisher: Netray (netray.co), AI and integration engineering for ERP and manufacturing systems.
> Section: Free Tools

## Short answer

Map common workpiece materials to the ISO P, M, K, N, S and H groups used on carbide insert and end mill catalogs.

## Category

manufacturing

## Industry

Machining

## Audience

- CNC programmer
- Tooling engineer
- Machinist

## Tool

**Kind:** worksheet

**Mode:** reference

**Columns:**

#### Workpiece material

**Key:** material

**Type:** text

#### Example designation

**Key:** example

**Type:** text

#### ISO group

**Key:** group

**Type:** text

#### Catalog colour

**Key:** colour

**Type:** text

#### Machining note

**Key:** note

**Type:** text

**Rows:**

**Material:** Low carbon steel

**Example:** AISI 1018, S235

**Group:** P

**Colour:** Blue

**Note:** Gummy, long chips. Use chip breaker geometry.

**Material:** Free machining steel

**Example:** AISI 12L14, 11SMn30

**Group:** P

**Colour:** Blue

**Note:** Good chip control, high speeds possible.

**Material:** Medium carbon steel

**Example:** AISI 1045, C45

**Group:** P

**Colour:** Blue

**Note:** General purpose group for coated carbide.

**Material:** Alloy steel (soft or annealed)

**Example:** AISI 4140, 42CrMo4

**Group:** P

**Colour:** Blue

**Note:** Reduce speed as hardness rises.

**Material:** Alloy steel (pre-hardened)

**Example:** 4140 at 28-34 HRC

**Group:** P

**Colour:** Blue

**Note:** Strong edge and heat resistant coating.

**Material:** Austenitic stainless steel

**Example:** AISI 304, 316

**Group:** M

**Colour:** Yellow

**Note:** Work hardens. Keep feed up, avoid rubbing.

**Material:** Precipitation hardening stainless

**Example:** 17-4 PH

**Group:** M

**Colour:** Yellow

**Note:** Condition dependent, tougher when aged.

**Material:** Duplex stainless steel

**Example:** 2205 (UNS S32205)

**Group:** M

**Colour:** Yellow

**Note:** High strength, high cutting forces.

**Material:** Gray cast iron

**Example:** ASTM A48 Class 30

**Group:** K

**Colour:** Red

**Note:** Short chips, abrasive. Often run dry.

**Material:** Ductile (nodular) cast iron

**Example:** ASTM A536 65-45-12

**Group:** K

**Colour:** Red

**Note:** Tougher than gray iron, coated carbide.

**Material:** Aluminum alloy (wrought)

**Example:** 6061-T6, 7075-T6

**Group:** N

**Colour:** Green

**Note:** Sharp uncoated or PCD edges, high speeds.

**Material:** Aluminum alloy (high silicon cast)

**Example:** A390, A356

**Group:** N

**Colour:** Green

**Note:** Abrasive silicon, PCD tools extend life.

**Material:** Copper alloys

**Example:** C110 copper, C360 brass

**Group:** N

**Colour:** Green

**Note:** Brass is easy, pure copper is gummy.

**Material:** Plastics

**Example:** Delrin (POM), nylon, PEEK

**Group:** N

**Colour:** Green

**Note:** Sharp edges, low heat, avoid melting.

**Material:** Titanium alloy

**Example:** Ti-6Al-4V (Grade 5)

**Group:** S

**Colour:** Orange

**Note:** Low speed, high coolant, sharp edges.

**Material:** Nickel based superalloy

**Example:** Inconel 718, Inconel 625

**Group:** S

**Colour:** Orange

**Note:** Work hardens, ceramics at high speed.

**Material:** Cobalt based alloy

**Example:** Stellite, Haynes 25

**Group:** S

**Colour:** Orange

**Note:** Very abrasive and tough.

**Material:** Hardened steel

**Example:** AISI 4340 at 50 HRC

**Group:** H

**Colour:** Grey

**Note:** CBN or fine grain carbide.

**Material:** Hardened tool steel

**Example:** AISI D2 at 58-62 HRC

**Group:** H

**Colour:** Grey

**Note:** CBN inserts, rigid setup, light cuts.

**Notes:** Group assignments follow the ISO 513 style grouping used by major insert catalogs. Individual manufacturers subdivide each group (for example P10 to P50) and may place borderline alloys differently, so confirm in the catalog you buy from.

## Content

**Intro:** Insert and end mill catalogs sort every grade by six colour coded ISO groups. Knowing which group your workpiece falls in is the first step to choosing a grade, geometry and starting speed. This reference lists common materials with their group.

**Sections:**

#### How to use the reference

**Body:** Search for your workpiece material or alloy designation, note the ISO group letter, then open the tooling catalog at that group. Grades are labelled with the group letter and a number, where lower numbers favour wear resistance and higher numbers favour toughness. Export the table if you want a reference page in your tooling standard.

#### What the six groups mean

**Body:** P is steel, M is stainless steel, K is cast iron, N is non-ferrous metals and plastics, S is heat resistant superalloys and titanium, and H is hardened steel. The colour code is blue, yellow, red, green, orange and grey respectively. The groups reflect how chips form and what tool wear mechanism dominates, not just hardness.

**Bullets:**

- P blue: steel
- M yellow: stainless
- K red: cast iron
- N green: non-ferrous and plastics
- S orange: titanium and superalloys
- H grey: hardened steel

#### Using group data in a tooling database

**Body:** Store the ISO group on every material record in your ERP or tool crib system. That lets a program or a planner filter approved insert grades by material instead of keeping a separate spreadsheet. It also helps when a customer changes the material on a drawing, because the affected tools and cutting data are easy to find.

#### Common mistakes

**Body:** Do not assume all stainless steels behave alike, since free machining 303 is easier than 316, and do not use a steel grade on titanium because heat concentrates at the edge. Another common error is treating hardness as the only factor: pre-hardened 4140 at 30 HRC is still a P material, while 50 HRC steel moves to H.

**Cta:** If material and tooling rules are scattered across spreadsheets, we can show how an ERP-connected assistant could answer which tool to use for a given part and material.

**Faq:**

#### What does P M K N S H stand for?

**Answer:** They are the six ISO material groups used by cutting tool makers: P for steel, M for stainless steel, K for cast iron, N for non-ferrous metals, S for heat resistant alloys and titanium, and H for hardened steel.

#### Which group is aluminum?

**Answer:** Aluminum alloys are in the N group, shown in green. High silicon cast aluminum is abrasive and often needs PCD tooling, while wrought alloys like 6061 and 7075 are machined with sharp, polished carbide.

#### Which group is Inconel and titanium?

**Answer:** Both belong to the S group, shown in orange. They are machined at much lower cutting speeds than steel because of heat and work hardening, and need rigid setups and plenty of coolant.

#### Can one insert cut several groups?

**Answer:** Some multi-purpose grades list more than one group, for example P and M, but performance is a compromise. For production work, pick the grade that is rated for your group and operation type.

## Search terms

iso material groups p m k n s h, insert material group chart, iso 513 cutting tool groups, carbide insert material classification, p m k n s h machining, which insert for stainless steel, insert grade selection chart, workpiece material group for tooling

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