The ISO 513 standard defines six primary workpiece material groups for metal cutting applications, designated as P, M, K, N, S, and H. Each group exhibits distinct machining characteristics that demand specific insert grades, geometries, and cutting parameters. This guide delivers comprehensive cutting data and insert recommendations for precision turning operations across all ISO material classifications.
Understanding ISO 513 Material Classification
ISO 513 categorizes workpiece materials based on machinability, chip formation behavior, and thermal load on the cutting edge. Proper material identification is the foundation for selecting optimal cutting speeds, feed rates, and depth of cut values.
| ISO Group | Material Category | Typical Materials | Machinability Index |
|---|---|---|---|
| P | Steel and Cast Steel | C15, C45, 42CrMo4, 100Cr6 | Good |
| M | Stainless Steel | X5CrNi18-10, X6CrNiMoTi17-12-2 | Moderate |
| K | Cast Iron | GG25, GGG50, GJL-250 | Good to Excellent |
| N | Non-Ferrous Metals | AlSi10Mg, CuZn37, Al7075-T6 | Excellent |
| S | Superalloys and Titanium | Inconel 718, Ti-6Al-4V, Hastelloy C | Poor |
| H | Hardened Steel | 55 HRC, 60 HRC, 62 HRC tool steel | Very Poor |
Cutting Speed (Vc) Reference Tables
Cutting speed remains the most critical parameter for tool life and productivity. The following tables provide starting values for uncoated, PVD-coated, and CVD-coated carbide inserts in continuous turning operations.
P-Group: Steel Turning Parameters
| Steel Type | Hardness (HB) | Vc (m/min) Uncoated | Vc (m/min) PVD | Vc (m/min) CVD | fn (mm/rev) | ap (mm) |
|---|---|---|---|---|---|---|
| Low-carbon steel (C15) | 125-175 | 180-250 | 280-350 | 260-320 | 0.15-0.40 | 1.0-4.0 |
| Medium-carbon steel (C45) | 170-210 | 150-200 | 240-300 | 220-280 | 0.12-0.35 | 1.0-4.0 |
| Alloy steel (42CrMo4) | 200-280 | 100-150 | 180-240 | 160-220 | 0.10-0.30 | 1.0-3.0 |
| Bearing steel (100Cr6) | 220-300 | 80-120 | 140-190 | 130-180 | 0.08-0.25 | 0.5-2.5 |
| Free-cutting steel (11SMn30) | 140-190 | 200-280 | 300-380 | 280-350 | 0.15-0.45 | 1.5-5.0 |
M-Group: Stainless Steel Turning Parameters
| Stainless Steel Grade | Type | Vc (m/min) PVD | Vc (m/min) CVD | fn (mm/rev) | ap (mm) |
|---|---|---|---|---|---|
| X5CrNi18-10 (304) | Austenitic | 120-160 | 140-180 | 0.12-0.30 | 1.0-3.0 |
| X6CrNiMoTi17-12-2 (316Ti) | Austenitic | 100-140 | 120-160 | 0.10-0.25 | 1.0-3.0 |
| X6Cr17 (430) | Ferritic | 140-180 | 160-200 | 0.12-0.35 | 1.0-4.0 |
| X5CrNiMo17-12-2 (316L) | Austenitic | 90-130 | 110-150 | 0.10-0.25 | 1.0-3.0 |
| X20Cr13 (420) | Martensitic | 100-140 | 120-160 | 0.10-0.28 | 1.0-3.0 |
K-Group: Cast Iron Turning Parameters
| Cast Iron Type | Hardness (HB) | Vc (m/min) Uncoated | Vc (m/min) CVD | Vc (m/min) Ceramic | fn (mm/rev) | ap (mm) |
|---|---|---|---|---|---|---|
| Gray cast iron (GG25) | 180-260 | 120-180 | 200-280 | 400-600 | 0.15-0.50 | 1.0-6.0 |
| Ductile iron (GGG50) | 170-250 | 100-150 | 160-220 | 300-450 | 0.12-0.40 | 1.0-5.0 |
| Malleable cast iron | 150-220 | 130-190 | 220-300 | 450-650 | 0.15-0.50 | 1.0-6.0 |
| Vermicular graphite iron | 160-240 | 110-160 | 180-250 | 350-500 | 0.12-0.40 | 1.0-5.0 |
| High-strength CGI (GGG70) | 220-300 | 80-120 | 140-190 | 250-380 | 0.10-0.30 | 0.8-3.0 |
N-Group: Non-Ferrous Metal Turning Parameters
| Material | Hardness (HB) | Vc (m/min) Uncoated | Vc (m/min) PCD | fn (mm/rev) | ap (mm) |
|---|---|---|---|---|---|
| Aluminum wrought (Al7075) | 60-90 | 400-600 | 800-1500 | 0.10-0.40 | 0.5-5.0 |
| Aluminum cast (AlSi10Mg) | 70-100 | 300-450 | 600-1200 | 0.10-0.35 | 0.5-4.0 |
| Copper (CuZn37) | 80-120 | 250-400 | 500-900 | 0.10-0.40 | 0.5-4.0 |
| Brass (CuZn39Pb3) | 90-140 | 200-350 | 400-800 | 0.10-0.45 | 0.5-5.0 |
| Magnesium (AZ91D) | 50-70 | 500-800 | 1000-2000 | 0.15-0.50 | 0.5-6.0 |
S-Group: Superalloy and Titanium Turning Parameters
| Material | Hardness (HB) | Vc (m/min) PVD | Vc (m/min) Ceramic | fn (mm/rev) | ap (mm) |
|---|---|---|---|---|---|
| Ti-6Al-4V (Grade 5) | 280-340 | 40-70 | 80-120 | 0.08-0.20 | 0.5-2.5 |
| Ti-6Al-4V ELI | 260-310 | 45-75 | 90-130 | 0.08-0.22 | 0.5-2.5 |
| Inconel 718 | 350-450 | 20-40 | 60-100 | 0.08-0.18 | 0.3-2.0 |
| Hastelloy C-276 | 200-280 | 15-30 | 50-80 | 0.06-0.15 | 0.3-1.5 |
| Waspaloy | 300-380 | 18-35 | 55-90 | 0.06-0.15 | 0.3-1.5 |
H-Group: Hardened Steel Turning Parameters
| Hardness (HRC) | Material Type | Vc (m/min) CBN | Vc (m/min) Ceramic | fn (mm/rev) | ap (mm) |
|---|---|---|---|---|---|
| 45-50 HRC | Tool steel / Die steel | 120-180 | 150-220 | 0.08-0.20 | 0.1-0.8 |
| 50-55 HRC | Cold work steel | 100-150 | 120-180 | 0.06-0.15 | 0.1-0.6 |
| 55-60 HRC | High-speed steel | 80-120 | 100-150 | 0.05-0.12 | 0.05-0.5 |
| 60-62 HRC | Bearing steel | 60-100 | 80-120 | 0.04-0.10 | 0.05-0.4 |
| 62-65 HRC | Carbide / Powder metallurgy | 40-70 | 60-90 | 0.03-0.08 | 0.03-0.3 |
Insert Grade Selection by Material Group
Selecting the correct insert substrate and coating combination maximizes tool life and surface finish quality. The following matrix maps common commercial grades to ISO material groups.
| ISO Group | Sandvik Coromant | Iscar | Kyocera | Walter | Mitsubishi |
|---|---|---|---|---|---|
| P (Steel) | GC4215, GC4325, GC4415 | IC9150, IC9250, IC9350 | CA515, CA525, CA530 | WPP10, WPP20, WPP30 | VP15TF, UE6110, US735 |
| M (Stainless) | GC2015, GC2025, GC2035 | IC907, IC908, IC910 | CA6535, CA6505 | WMP20, WMP30 | VP20RT, MP9120 |
| K (Cast Iron) | GC3215, GC3225, GC3305 | IC330, IC530N | CA310, CA360 | WPP10S, WPP20S | UE6020, UC5115 |
| N (Non-Ferrous) | H13A, N123H2-0400-0010 | IC20, IC28 | DLC-coated KPD001 | WNN15, WNN20 | HTi10, NX2525 |
| S (Superalloys) | H13A, S05F, S10T | IC500A, IC900 | CA3105, PR15 | WSM10, WSM20 | VP15RT, MP9015 |
| H (Hardened) | CB7015, CB7025, CB7050 | IC1007, IC1010 | KB9630, KPD010 | WSM33S, WBK20 | BC8020, BC8110 |
Feed Rate and Depth of Cut Optimization
Beyond cutting speed, feed rate (fn) and depth of cut (ap) determine chip thickness, cutting forces, and surface integrity. The following guidelines apply to 80-degree rhombic (CNMG) and triangular (TNMG) inserts with 0.8 mm nose radius.
Roughing Operations
- Depth of cut (ap): 2.0-6.0 mm for stable conditions, 1.0-2.0 mm for slender workpieces
- Feed rate (fn): 0.25-0.50 mm/rev for P/K groups, 0.15-0.30 mm/rev for M/S/H groups
- Lead angle approach: 75-95 degrees preferred for lowest radial forces
- Chip breaker requirement: Open geometry (NR, NM) for deep cuts
Medium Machining
- Depth of cut (ap): 1.0-3.0 mm
- Feed rate (fn): 0.15-0.30 mm/rev for P/K, 0.10-0.20 mm/rev for M/S/H
- Insert geometry: Medium chip breaker (MM, MP)
- Surface finish target: Ra 1.6-3.2 μm
Finishing Operations
- Depth of cut (ap): 0.1-1.0 mm
- Feed rate (fn): 0.05-0.15 mm/rev depending on nose radius
- Nose radius selection: 0.4 mm for fine finish, 0.8 mm for general finish, 1.2 mm for stronger edge
- Surface finish target: Ra 0.4-1.6 μm
Comparative Analysis: PVD vs CVD Coatings
Coating technology significantly influences parameter selection. PVD coatings operate at lower temperatures with sharper edges, while CVD coatings withstand higher thermal loads but require slightly reduced speeds to manage thermal shock.
| Characteristic | PVD (TiAlN, AlCrN) | CVD (TiCN-Al2O3-TiN) |
|---|---|---|
| Coating thickness | 2-6 μm | 8-15 μm |
| Edge sharpness | Sharp ( honed 0.01-0.03 mm) | Moderate ( honed 0.03-0.08 mm) |
| Max cutting temp | 800-900 degrees C | 1000-1100 degrees C |
| Best application | M, S, H groups; interrupted cuts | P, K groups; continuous cuts |
| Typical Vc adjustment | Base speed +10-20% | Base speed (reference) |
| Tool life multiplier | 2-4x vs uncoated | 3-6x vs uncoated |
Practical Machining Scenarios
Scenario 1: Shaft Turning in 42CrMo4 (P-Group)
A 65 mm diameter shaft requires roughing from 67 mm to 65.5 mm, followed by finishing to 65h7. Using a Sandvik Coromant CNMG 12 04 08-WM GC4325 insert:
- Roughing: Vc = 220 m/min, fn = 0.30 mm/rev, ap = 0.75 mm
- Spindle speed: n = 1000 x 220 / (pi x 67) = 1045 rpm
- Finishing: Vc = 260 m/min, fn = 0.12 mm/rev, ap = 0.25 mm
- Spindle speed: n = 1000 x 260 / (pi x 65.5) = 1263 rpm
- Result: Ra 0.8 μm, tool life 45 minutes
Scenario 2: Inconel 718 Aerospace Component (S-Group)
A turbine disk flange with 120 mm diameter requires external turning. Using an Iscar CNMG 12 04 04-SM IC500A insert with high-pressure coolant:
- Roughing: Vc = 30 m/min, fn = 0.15 mm/rev, ap = 1.5 mm
- Spindle speed: n = 1000 x 30 / (pi x 120) = 80 rpm
- Coolant pressure: 70-100 bar directed at cutting edge
- Result: 12 minutes edge life, acceptable for indexable tooling
Scenario 3: Hardened Bearing Ring (H-Group)
A 62 HRC bearing ring (100Cr6) requires hard turning as a grinding replacement. Using a Kyocera KB9630 CBN insert:
- Finishing: Vc = 90 m/min, fn = 0.08 mm/rev, ap = 0.15 mm
- Spindle speed: n = 1000 x 90 / (pi x 80) = 358 rpm
- Surface finish: Ra 0.4 μm, comparable to grinding
- Tool life: 25 minutes per edge, Cpk greater than 1.67
Troubleshooting Common Parameter Issues
| Problem | Possible Cause | Corrective Action |
|---|---|---|
| Rapid flank wear | Vc too high; grade too soft | Reduce Vc by 15-20%; select harder grade |
| Built-up edge (BUE) | Vc too low; fn too small | Increase Vc by 20-30%; increase fn to 0.15 mm/rev minimum |
| Chipping / breakage | ap too large; interrupted cut | Reduce ap; select stronger edge (SF, SR); reduce feed 10% |
| Poor surface finish | fn too high; nose radius too small | Reduce fn by 30%; increase nose radius to 0.8 or 1.2 mm |
| Excessive vibration | Overhang too long; ap/fn mismatch | Reduce tool overhang; increase ap and reduce fn proportionally |
Conclusion
ISO 513 material classification provides a systematic framework for parameter selection in turning operations. The cutting speed ranges, feed rates, and depth of cut values presented in this guide serve as validated starting points for productive machining across all six material groups. Always begin at the conservative end of the recommended range, then optimize based on machine stability, coolant delivery, and surface finish requirements. Modern coated grades from Sandvik Coromant, Iscar, Kyocera, Walter, and Mitsubishi extend these parameter windows significantly, but the fundamental relationships between material machinability and cutting data remain constant across all platforms.
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