Introduction
Selecting the right carbide grade for a machining operation is one of the most consequential decisions a manufacturing engineer makes. The ISO carbide grade classification system — P, M, K, N, S, and H — provides a universal language for matching cutting tool materials to workpiece materials, but translating these broad categories into actionable cutting parameters requires detailed reference data.
This comprehensive reference article compiles recommended cutting speed (Vc), feed per tooth (fz), feed per revolution (f), depth of cut (ap), and width of cut (ae) ranges for each ISO grade class across turning, milling, and drilling operations. We also include cross-brand grade equivalents from Kyocera, TaeguTec, and Korloy to help you quickly identify comparable grades when switching suppliers or optimizing an existing process.
All parameters presented are general starting recommendations. Actual values must be adjusted based on machine rigidity, tool holder type, coolant delivery, workpiece condition, and required surface finish.
Understanding the ISO Carbide Grade Classification System
The ISO 513 standard classifies carbide cutting grades into six main categories based on the primary workpiece material they are designed to machine. Each category is identified by a letter and a color code, with numerical suffixes (01, 05, 10, 20, 30, 40, 50) indicating the position on the wear resistance vs. toughness spectrum. Lower numbers favor wear resistance and higher cutting speeds; higher numbers favor toughness and interrupted cuts.
| ISO Class | Color | Primary Workpiece Material | Key Machining Challenge |
|---|---|---|---|
| P | Blue | Steel, carbon steel, alloy steel, ferritic/martensitic stainless | Built-up edge, crater wear, high cutting temperatures |
| M | Yellow | Austenitic stainless steel, duplex stainless, manganese steel | Work hardening, chip control, thermal conductivity |
| K | Red | Cast iron (gray, ductile, compacted graphite) | Abrasive wear, chipping, discontinuous chip |
| N | Green | Non-ferrous metals (aluminum, copper, brass, plastics) | Built-up edge, surface finish, low melting point |
| S | Orange | Heat-resistant alloys, superalloys, titanium, nickel-base | Extreme work hardening, high temperature strength, poor conductivity |
| H | Gray | Hardened steel, chilled cast iron, hard-facing materials (45-65 HRC) | Extreme abrasion, high temperatures, tool deflection |
Within each class, the numerical suffix indicates the application range:
- 01–05: Finishing to light roughing, high speed, low feed, high wear resistance
- 10–20: General-purpose turning and milling, medium speed and feed
- 30–40: Roughing and interrupted cuts, lower speed, higher feed, high toughness
- 50: Heavy roughing, severe interruptions, very tough grades, low cutting speed
Turning Cutting Parameters Reference
The following table provides recommended starting parameters for external longitudinal turning with carbide inserts. Values assume rigid setup, through-tool coolant where applicable, and standard insert geometries (CNMG, DNMG, SNMG, VNMG).
| ISO Class | Workpiece Material | Vc (m/min) | f (mm/rev) | ap (mm) | Coolant |
|---|---|---|---|---|---|
| P01 | Carbon steel < 800 N/mm² | 300–450 | 0.08–0.15 | 0.2–1.0 | Emulsion or MQL |
| P10 | Carbon/alloy steel < 1000 N/mm² | 200–350 | 0.10–0.25 | 0.5–3.0 | Emulsion |
| P20 | Alloy steel < 1200 N/mm² | 120–250 | 0.15–0.40 | 1.0–4.0 | Emulsion / Flood |
| P30 | Alloy steel, forged, scaled | 80–180 | 0.20–0.50 | 2.0–6.0 | Flood coolant |
| P40 | High-alloy steel, heavy roughing | 50–120 | 0.30–0.70 | 3.0–8.0 | Flood coolant |
| M10 | Austenitic stainless, solution treated | 150–250 | 0.08–0.20 | 0.3–2.0 | High-pressure coolant |
| M20 | Austenitic/duplex stainless | 100–180 | 0.12–0.30 | 0.5–3.0 | High-pressure coolant |
| M30 | Duplex/superduplex, cast stainless | 60–120 | 0.15–0.40 | 1.0–4.0 | Flood + high pressure |
| K05 | Gray cast iron, continuous cut | 250–400 | 0.08–0.15 | 0.3–1.5 | Dry or emulsion |
| K10 | Gray cast iron, general turning | 180–300 | 0.10–0.25 | 0.5–3.0 | Dry or emulsion |
| K20 | Ductile cast iron (GGG) | 120–220 | 0.12–0.30 | 0.5–3.0 | Emulsion |
| K30 | Cast iron with sand inclusions, CGI | 70–150 | 0.15–0.40 | 1.0–4.0 | Flood coolant |
| N10 | Aluminum alloys > 6% Si | 500–1500 | 0.08–0.20 | 0.3–2.0 | Dry or MQL |
| N20 | Aluminum, copper, brass | 300–800 | 0.10–0.30 | 0.5–4.0 | Dry or emulsion |
| S05 | Titanium alloys (Ti6Al4V), continuous | 60–100 | 0.08–0.15 | 0.3–1.5 | High-pressure coolant |
| S10 | Inconel 718, solution treated | 40–80 | 0.10–0.20 | 0.5–2.0 | High-pressure coolant |
| S20 | Nickel-base alloys, aged | 25–55 | 0.12–0.25 | 0.5–3.0 | Flood + high pressure |
| S30 | Waspaloy, Rene, cast superalloys | 15–35 | 0.15–0.30 | 1.0–3.0 | High-pressure coolant |
| H05 | Hardened steel 58–65 HRC, finishing | 80–150 | 0.05–0.12 | 0.1–0.5 | Dry or air blast |
| H10 | Hardened steel 50–60 HRC | 50–100 | 0.08–0.18 | 0.2–1.0 | Dry or air blast |
| H20 | Hardened steel 45–55 HRC, roughing | 30–70 | 0.10–0.25 | 0.3–1.5 | Dry or emulsion |
Key takeaway for turning: ISO P20 and M20 grades are the workhorses of general machining, offering the best balance of wear resistance and toughness for most steel and stainless steel applications. Always start at the lower end of the Vc range and increase gradually while monitoring tool wear.
Milling Cutting Parameters Reference
Milling parameters differ significantly from turning due to the interrupted nature of the cut and multi-tooth engagement. The following values are for indexable end mills and face mills with carbide inserts, assuming a radial engagement ae/D ratio of 0.3–0.5 for general milling.
| ISO Class | Workpiece Material | Vc (m/min) | fz (mm/tooth) | ap (mm) | ae/D Ratio |
|---|---|---|---|---|---|
| P10 | Carbon steel < 800 N/mm², finishing | 200–350 | 0.08–0.15 | 0.5–2.0 | 0.2–0.4 |
| P20 | Carbon/alloy steel, general milling | 120–250 | 0.10–0.25 | 1.0–4.0 | 0.3–0.6 |
| P30 | Alloy steel, roughing, scale | 60–150 | 0.15–0.35 | 2.0–6.0 | 0.5–1.0 |
| M10 | Austenitic stainless, finishing | 120–200 | 0.06–0.12 | 0.5–2.0 | 0.2–0.4 |
| M20 | Stainless steel, general milling | 80–150 | 0.08–0.18 | 1.0–3.0 | 0.3–0.5 |
| M30 | Duplex stainless, roughing | 50–100 | 0.10–0.25 | 1.5–4.0 | 0.4–0.7 |
| K10 | Gray cast iron, face milling | 200–350 | 0.10–0.20 | 1.0–4.0 | 0.5–1.0 |
| K20 | Ductile cast iron, general | 120–220 | 0.12–0.25 | 1.0–3.0 | 0.4–0.7 |
| N10 | Aluminum alloys, high-speed milling | 1000–3000 | 0.05–0.15 | 0.5–5.0 | 0.3–0.8 |
| N20 | Aluminum casting, copper alloys | 500–1500 | 0.08–0.20 | 1.0–6.0 | 0.4–0.8 |
| S10 | Titanium Ti6Al4V, finishing | 50–90 | 0.06–0.12 | 0.5–2.0 | 0.1–0.3 |
| S20 | Inconel 718, general milling | 25–50 | 0.08–0.15 | 1.0–3.0 | 0.1–0.3 |
| S30 | Nickel-base alloys, roughing | 15–35 | 0.10–0.20 | 1.0–4.0 | 0.15–0.4 |
| H10 | Hardened steel 55–62 HRC | 60–120 | 0.05–0.10 | 0.3–1.0 | 0.2–0.4 |
| H20 | Hardened steel 45–55 HRC | 40–80 | 0.08–0.15 | 0.5–2.0 | 0.3–0.5 |
Important note: For milling operations, the radial engagement (ae/D ratio) dramatically affects tool life. When using full slotting (ae/D = 1.0), reduce Vc by 30–50% compared to the values shown. Conversely, for light radial engagement (ae/D < 0.1), Vc can often be increased by 20–40% due to reduced cutting time per tooth.
Drilling Cutting Parameters Reference
Drilling parameters for indexable insert drills and solid carbide drills follow different regimes. The table below covers both indexable insert drills (3–5×D) and solid carbide drills (8–12×D) with internal coolant.
| ISO Class | Workpiece Material | Vc (m/min) Indexable | Vc (m/min) Solid Carbide | f (mm/rev) | Coolant Pressure |
|---|---|---|---|---|---|
| P15 | Carbon steel < 800 N/mm² | 120–200 | 100–180 | 0.10–0.25 | 10–20 bar |
| P25 | Alloy steel < 1000 N/mm² | 80–150 | 70–130 | 0.12–0.28 | 15–25 bar |
| M20 | Austenitic stainless steel | 60–100 | 50–90 | 0.08–0.18 | 20–30 bar |
| K15 | Gray cast iron | 100–180 | 90–160 | 0.10–0.25 | 10–20 bar |
| K20 | Ductile cast iron | 70–120 | 60–110 | 0.10–0.22 | 15–25 bar |
| N10 | Aluminum alloys | 200–400 | 150–300 | 0.12–0.30 | 5–15 bar |
| S15 | Titanium alloys | 30–60 | 25–50 | 0.06–0.15 | 20–40 bar |
| S25 | Nickel-base superalloys | 15–35 | 12–30 | 0.05–0.12 | 25–45 bar |
Cross-Brand Grade Equivalent Chart
One of the biggest challenges in multi-brand workshop environments is finding equivalent grades across different manufacturers. The following chart provides approximate grade equivalents for Kyocera, TaeguTec, and Korloy across the main ISO classes. Note that these are approximate matches — always verify with the manufacturer’s technical data for the specific application.
Turning Grade Equivalents
| ISO Class | Kyocera | TaeguTec | Korloy | Typical Coating |
|---|---|---|---|---|
| P01–P10 | CA5525 | TT9080 | NC3020 | CVD TiCN-Al₂O₃-TiN |
| P10–P20 | CA5535 | TT8115 | NC3030 | CVD TiCN-Al₂O₃-TiN |
| P20–P30 | CA5515 | TT8125 | NC3120 | CVD TiCN-Al₂O₃ |
| P30–P40 | TN6020 | TT7220 | NC3220 | PVD TiAlN / TiN |
| M10–M20 | PV720 | TT9030 | NC3030 | CVD TiCN-Al₂O₃ |
| M20–M30 | TN610 | TT8020 | NC3130 | PVD TiAlN |
| K05–K10 | CA4515 | TT7070 | NC3010 | CVD Al₂O₃-TiCN |
| K10–K20 | CA4525 | TT7080 | NC3020 | CVD Al₂O₃-TiCN |
| K20–K30 | TN5415 | TT6080 | NC3110 | PVD TiN / TiCN |
| N10–N20 | KB5330 | TD930 | NC010 | Uncoated / PCD-tipped |
| S05–S15 | CR7015 | TT7015 | PC9030 | PVD TiAlN+TiN |
| S15–S25 | CR7025 | TT7025 | PC9035 | PVD AlTiN |
| H05–H10 | BN700 | TT7500 | PC9530 | CBN / PVD Al₂O₃ |
| H10–H20 | BN500 | TT7300 | PC8110 | PVD AlTiN |
Milling Grade Equivalents
| ISO Class | Kyocera | TaeguTec | Korloy | Insert Type |
|---|---|---|---|---|
| P10–P20 | PG025 | TT9080 | MP3030 | APKT, SEKT face mill |
| P20–P30 | PG035 | TT8125 | MP3130 | APKT, BAP end mill |
| M10–M20 | MG015 | TT9030 | MM3020 | APKT, SEKT |
| M20–M30 | MG025 | TT8020 | MM3120 | High-feed, roughing |
| K10–K20 | KG020 | TT7080 | MK3010 | SEKT, OFKT face mill |
| S10–S20 | SG015 | TT7015 | MS9025 | Ball nose, end mill |
| H10–H20 | HG010 | TT7300 | MH8010 | Finishing end mill |
Grade Selection Decision Framework
Choosing the correct grade involves balancing multiple factors. Use this decision framework when selecting or optimizing a grade:
1. Define the Primary Failure Mode
- Flank wear / crater wear dominant: Move to a more wear-resistant grade (lower ISO number) with higher hot hardness
- Chipping / fracture dominant: Move to a tougher grade (higher ISO number) with higher transverse rupture strength
- Built-up edge (BUE): Consider a grade with a smoother coating surface or a PVD-coated grade with TiN top layer
- Thermal cracking: Switch to a CVD-coated grade with better thermal barrier properties or reduce cutting speed
- Notching: Increase feed rate slightly to move the notch position, or switch to a more notch-resistant grade
2. Consider the Operation Type
Continuous turning operations favor wear-resistant grades, while interrupted cuts (milling, slotting, roughing with scale) demand toughness. The severity of interruption determines how far you should move toward the tough end of the spectrum.
3. Factor in Coolant Availability
High-pressure coolant (70+ bar) can extend tool life by 30–100% in steel and stainless steel turning by reducing cutting zone temperature and improving chip evacuation. If high-pressure coolant is available, you can often run 15–25% higher cutting speeds with the same grade.
4. Account for Machine Rigidity
A rigid setup with short tool overhang, high-quality tool holders, and a well-maintained spindle allows for more aggressive parameters and favors wear-resistant grades. Flexible setups (long overhang, weak fixturing) require tougher grades and reduced parameters to avoid chatter and tool fracture.
Practical Application Examples
To illustrate how to use these reference tables, let’s walk through three common scenarios.
Example 1: Alloy Steel Rough Turning
Scenario: Rough turning 42CrMo4 alloy steel (approx. 900 N/mm² tensile strength) with a CNMG 120408 insert on a rigid CNC lathe with flood coolant. Depth of cut 4 mm, feed 0.4 mm/rev.
Grade selection: ISO P25–P30 range → Kyocera CA5515, TaeguTec TT8125, Korloy NC3120
Starting parameters: Vc = 150 m/min → n ≈ 1,200 rpm for Ø40 mm bar. Start at 120 m/min and increase in 10% steps while monitoring flank wear.
Example 2: Stainless Steel Milling
Scenario: Face milling 316L austenitic stainless steel with a 63 mm diameter face mill (8 inserts, SEKT 1204), ae = 40 mm (ae/D ≈ 0.63), ap = 2 mm. Machine has moderate rigidity, emulsion flood coolant.
Grade selection: ISO M20 → Kyocera MG015, TaeguTec TT9030, Korloy MM3020
Starting parameters: Vc = 120 m/min → n ≈ 600 rpm. fz = 0.12 mm/tooth → vf ≈ 575 mm/min. Monitor for built-up edge and reduce speed slightly if BUE forms.
Example 3: Ductile Iron Drilling
Scenario: Drilling GGG40 ductile cast iron with an indexable insert drill, Ø25 mm, 3×D depth, internal coolant at 20 bar.
Grade selection: ISO K20 → Drill-specific grades (check manufacturer’s drill grade catalog)
Starting parameters: Vc = 90 m/min → n ≈ 1,150 rpm. f = 0.15 mm/rev → vf ≈ 172 mm/min. Ensure adequate chip evacuation; reduce feed if chip packing occurs.
Optimization Tips and Common Pitfalls
- Always start conservatively. Begin at 70–80% of the recommended Vc and increase in 10–15% increments until the target tool life or wear rate is achieved.
- Monitor all wear modes. Don’t just check flank wear — crater wear, notching, chipping, and thermal cracking can all be the limiting factor depending on the application.
- Don’t over-toughen. Using a P40 grade for a continuous finishing operation wastes productivity. Match the grade to the severity of the cut, not just the workpiece material.
- Chipbreakers matter as much as grades. A great grade with the wrong chipbreaker geometry will perform poorly. Always select chipbreaker and grade together.
- Document everything. Keep a parameter log with workpiece material, grade, insert geometry, cutting parameters, tool life, and failure mode. This builds your shop’s knowledge base over time.
- Consider total cost, not just tool cost. A more expensive grade that runs 30% faster or lasts 50% longer almost always reduces total machining cost through higher productivity and fewer tool changes.
Conclusion
The ISO carbide grade classification system is an indispensable tool for manufacturing engineers, but its real value lies in translating those classifications into concrete cutting parameters and grade selections. The reference data in this article provides a solid starting point for turning, milling, and drilling operations across all six ISO grade classes.
Remember that these are general recommendations — every shop’s specific conditions (machine tools, fixtures, coolant systems, operator expertise) will influence the optimal parameters and grades. Use the cross-brand grade equivalent chart to quickly identify alternatives when switching between Kyocera, TaeguTec, and Korloy tools, but always validate with cutting tests on your actual equipment.
For application-specific recommendations or assistance with a particularly challenging machining operation, consult the manufacturer’s technical support team — most major tooling companies offer free application engineering support to help you optimize your processes.
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