TaeguTec NC Material Classification: Understanding the TT Grade System

TaeguTec, a major South Korean cutting tool manufacturer, uses its own material classification and grade designation system that differs from the standard ISO 513 P/M/K/N/S/H color-coded system used by most Western manufacturers. For machinists and engineers who are selecting TaeguTec inserts for the first time, understanding the TT grade system, the NC material codes, and how they map to ISO application categories is essential for making correct tooling decisions. This article provides a comprehensive guide to the TaeguTec classification system.

The TT Grade Naming Convention

TaeguTec designates its carbide grades using a prefix code that indicates the coating technology, followed by a numeric identifier that specifies the position within the application range. The most common prefixes include TT for standard CVD-coated turning grades, TTG for PVD-coated turning grades, and TTM for milling-specific grades. The numeric codes typically follow a pattern where the first digit indicates the primary material group and the remaining digits indicate the specific grade within that group.

For example, TT8020 is a CVD-coated grade for steel turning where the 8 indicates the CVD coating generation and 020 indicates the toughness-to-wear-resistance balance. TT5525 is a newer-generation CVD grade for general-purpose steel turning. TT7050 is a PVD-coated grade for stainless steel machining. Understanding these codes allows you to quickly identify the intended application without consulting the full catalog.

NC Material Classification System

TaeguTec’s NC (Numerically Controlled) material classification extends beyond simple grade naming to include a systematic categorization of workpiece materials. The NC system uses a two-part code: a letter group indicating the material family and a numeric code indicating the specific material condition.

The second and third digits in the NC code indicate the specific material condition. For example, NC210 represents normalized 1045 steel, NC220 represents cold-drawn 1045, and NC230 represents quenched and tempered 1045 at 28 to 32 HRC. This granularity allows TaeguTec to provide application-specific grade recommendations rather than generic ISO-class suggestions.

Primary Turning Grades

TaeguTec’s current turning grade lineup for steel includes several key products. The TT5525 is a CVD-coated grade with a multi-layer TiCN/Al2O3/TiN coating stack on a medium-grain substrate rated for ISO P15-P30. It is the most versatile grade in the lineup and is recommended as the first choice for general steel turning operations. The coating thickness is approximately 8 to 10 micrometers, and the substrate hardness is approximately 1500 HV.

The TT8020 uses a newer-generation CVD coating with enhanced alumina crystal orientation, similar in concept to Sandvik’s Inveio technology. It is rated for ISO P10-P25 and offers superior wear resistance for continuous cutting operations. The TT8015 is the hardest variant in the CVD turning line, rated for ISO P05-P20, targeting high-speed finishing of carbon steels at speeds above 350 m/min.

For stainless steel, the TT7050 PVD grade uses an AlTiN nano-layer coating on a sharp-edged substrate, rated for ISO M15-M30. Its primary advantage is resistance to built-up edge formation when machining austenitic stainless steels such as 304 and 316 at moderate speeds of 150 to 220 m/min.

Cutting Parameter Guidelines by NC Code

TaeguTec publishes recommended cutting parameters linked to its NC material codes. The following table provides representative parameters for the most common NC codes when using CNMG 120408 inserts with the HM chipformer:

Chipformer Designation System

TaeguTec uses a chipformer naming system that indicates the operation type and feed range. The HF chipformer handles heavy roughing at feeds of 0.30 to 0.60 mm/rev. The HM chipformer covers medium roughing and general turning at feeds of 0.20 to 0.45 mm/rev. The MM chipformer is for medium finishing at feeds of 0.15 to 0.30 mm/rev. The ML chipformer handles light finishing at feeds of 0.08 to 0.20 mm/rev. Each chipformer features progressively lighter edge preparation, from the HF’s 30 to 40 micrometer T-land to the ML’s 10 to 15 micrometer hone.

Grade Selection Decision Tree

TaeguTec recommends the following decision process for grade selection. First, identify the NC material code for your workpiece. Second, determine whether the cut is continuous or interrupted. For continuous cuts, select the hardest grade in the recommended range for maximum speed. For interrupted cuts, move one step toward the tougher end of the range. Third, match the chipformer to the operation type based on depth of cut and feed rate.

For example, turning 4140 steel shafts with keyways (interrupted cut) would proceed as follows: NC310 material code suggests TT5525 or TT5535. The interrupted cut condition moves the selection toward TT5535 for its tougher substrate. The roughing operation at 2.5 mm depth of cut and 0.30 mm/rev feed indicates the HM chipformer. The final specification would be CNMG 120408-HM TT5535.

Milling Grade System

TaeguTec’s milling grades use the TTM prefix and follow similar logic. The TTM5525 is a CVD-coated milling grade for steel at ISO P20-P35, suitable for face milling and shoulder milling operations. The TTM7050 is a PVD-coated grade for stainless steel milling. The TTM3030 targets cast iron milling at ISO K15-K30. Milling grades use thinner coatings than turning grades to maintain sharp cutting edges, with typical coating thicknesses of 2 to 4 micrometers for PVD and 4 to 6 micrometers for CVD.

Price-Performance Positioning

TaeguTec grades are typically priced 20 to 35 percent below equivalent Sandvik Coromant or Kennametal grades, while delivering approximately 85 to 95 percent of the performance in standard applications. This price-performance ratio makes TaeguTec attractive for high-volume production environments where insert consumption is a significant cost factor. In many job shops and contract manufacturing facilities, the TT5525 grade serves as the default steel-turning grade, providing acceptable performance across a wide range of materials at a competitive price point.

Conclusion

TaeguTec’s NC material classification and TT grade system provides a structured approach to cutting tool selection that, once understood, enables efficient and accurate grade matching for any machining application. The NC codes provide more specific material identification than the generic ISO P/M/K/N/S/H system, and the TT grade numbering convention encodes useful information about coating generation and performance positioning. By mapping your workpiece materials to NC codes and following TaeguTec’s decision tree for grade and chipformer selection, you can optimize tool life and productivity while benefiting from TaeguTec’s competitive pricing structure.