Seco Grade Chart & ISO Equivalents

Seco writes the ISO class into the grade code, which makes comparison across brands unusually straightforward. Here is the range, plus what the Duratomic claim actually buys you.

How a Seco grade code is built

Seco codes a grade by its application family first, then its position within that family. Two letters do the work:

• TP — turning, P class. The steel-turning line: TP1500, TP2500, TP3500, TP4000, with “1” variants (TP1501, TP2501, TP3501). The four digits are the ISO class, written out: 15 = P15, 25 = P25, 35 = P35, 40 = P40.
• CP — turning, M/S class. CP500 is the stainless and heat-resistant alloy grade.
• TS — turning, stainless. TS2500 sits alongside CP500 in stainless work.
• CBN / CM — hardened steel. CBN300 for the H class.

One practical advantage: Seco’s numbers are transparent. TP2500 is a P25 grade. You do not have to consult a chart to know where it sits — the code tells you.

Common Seco grades and their ISO classes

Seco revises its grade range between catalogue generations and the TP / CP / TS families have been through several. The ISO classes above follow the manufacturer's published positioning; availability of a specific code should always be confirmed at quotation.

Duratomic: what the name is actually claiming

Duratomic is Seco's alumina coating process. The claim is texture control in the Al₂O₃ layer — growing the crystals in a controlled orientation rather than randomly, then treating the surface. Seco positions the benefit as enhanced flank-wear resistance and a smoother, more predictable wear progression rather than a step change in peak performance.

Two things follow for a buyer:

• Predictable wear is worth more than maximum wear resistance in production. A tool that fails at a known point can be changed on schedule. A tool with variable life forces you to change early or scrap parts. If you are running unattended or lights-out, this is the property to buy.
• A coating claim you cannot verify is marketing. Alumina layers can be grown in controlled orientation by more than one plant. What separates them is whether the thickness and adhesion are consistent batch to batch. That is measurable, so we measure it: ball-crater for thickness, Rockwell indentation for spalling.

The numbering convention is your leverage

Because Seco writes the ISO class into the code, you can compare across brands without a lookup table. A quote offering “an equivalent to TP2500” is offering a P25 grade. Ask what the cobalt content and grain size are, and ask what coating thickness will be delivered — those three answers tell you whether it is genuinely the same class of tool or just a similar label.