Material Guide

Why group the materials at all

ISO 513 sorts workpiece materials into six groups by machining behaviour rather than by metallurgy. Two alloys with quite different compositions belong in the same group when they load, heat and wear an edge in the same way — and that is the only similarity a machinist needs when selecting a tool.

The value of the grouping is diagnostic. If you know the group, you know in advance which failure mode is most likely, which parameter is the sensitive one, and which coolant strategy is worth the trouble. The ISO Material Classification guide covers the classification itself; this page covers what each group does to a tool.

P — steel

The largest group: unalloyed, low-alloy and high-alloy steels, plus cast steel. Chips are generally long and continuous. The dominant wear mechanism is crater wear on the rake face, driven by temperature at the chip-tool interface.

What works: a stable, uninterrupted cut at a moderate speed with a chip load high enough to keep the edge shearing. Steel is forgiving of a wide parameter window, which is precisely why steel jobs so often run far below their capability. Free-machining and low-carbon grades tend towards built-up edge at low speeds; raising the speed usually cures it.

M — stainless steel

Austenitic, ferritic, martensitic and duplex stainless steels. Two properties dominate: they work-harden rapidly, and they conduct heat poorly, so the heat stays at the edge.

What works: a positive, sharp geometry and a chip load deliberately on the high side — the edge must get under the previously hardened layer rather than skimming it. Never dwell in the cut, never let the tool rub, and avoid re-cutting a surface that has already been passed over lightly. Rigidity and abundant, well-aimed coolant matter more here than in P-group work. Duplex grades combine the work-hardening tendency with higher strength and are correspondingly harder again.

K — cast iron

Grey, nodular (ductile) and compacted graphite irons. Chips are short and break naturally; the wear mechanism is abrasion, not heat, because the graphite structure and any cast skin act as an abrasive.

What works: hard, wear-resistant edge preparation and a stable cut. Cast skin and sand inclusions are the real hazard — the first pass on an unmachined casting is an interrupted cut through abrasive material, and it should be taken deeper than the skin rather than skimming along it. Many cast-iron operations run dry: the chips do not need flushing, and thermal cycling from intermittent coolant can crack an edge.

N — non-ferrous

Aluminium alloys, copper, brass, bronze and non-metallics. Cutting speeds are an order of magnitude above the ferrous groups; the constraint is not heat at the edge but getting the chip out of the flute and the spindle's ability to turn fast enough.

What works: low flute counts with large chip space, sharp positive geometry, high polish in the flute to prevent adhesion, and generous chip evacuation — through-spindle coolant or air blast. Aluminium's characteristic failure is welding to the edge: a built-up edge forms, breaks away with a piece of the coating, and the surface finish collapses. High silicon content changes the picture, adding hard abrasive particles to an otherwise gummy matrix.

S — heat-resistant superalloys and titanium

Nickel and cobalt-based alloys, and titanium alloys. These retain their strength at temperature — which is the point of them — so the heat generated in cutting stays concentrated in a very small zone at the edge instead of leaving in the chip.

What works: low cutting speed, a firm chip load, and constant engagement. Notch wear at the depth-of-cut line is the characteristic failure; varying the axial depth between passes spreads it rather than concentrating it at one point on the edge. Titanium adds chemical reactivity and a low elastic modulus: the material springs away from the tool and back into it, so rigidity and a sharp edge matter enormously, and high-pressure coolant is frequently the difference between a viable process and a scrapped part.

H — hardened materials

Hardened and tempered steels above roughly 45 HRC, hardened cast irons and chilled irons. Hard milling replaces a grinding or EDM operation, and its economics depend on holding a very stable, light cut.

What works: light radial and axial engagement, high rigidity, minimal stickout, and edge preparation appropriate for the hardness. Deflection is the enemy: a hard material does not yield, so anything that moves is the tool. Interrupted cuts and re-entry into a partially cut region are far more damaging here than in soft material. See the Hardness Guide for what the hardness figure implies.

Summary — failure mode by group

Material recommendations, ISO application ranges and recommended workpiece hardness for EUROCUTPRECISION tools are pending final manufacturer confirmation and are not published on any product page until they are confirmed. The guidance above is general practice for solid carbide milling and applies to the material, not to a particular tool.