Walter Turning Grade Naming Convention Explained
Walter AG, headquartered in Tübingen, Germany, employs a systematic naming convention for its turning insert grades that directly encodes coating technology, ISO material group, and application range. Understanding this nomenclature is essential for selecting the correct insert for any workpiece material.
The Walter grade code follows a three-letter-plus-number format:
- First letter (W) — Identifies the manufacturer (Walter).
- Second letter — Indicates the coating technology: A = CVD (chemical vapor deposition), P = PVD (physical vapor deposition), K = ceramic, H = CBN (cubic boron nitride), N = uncoated.
- Third letter — Corresponds to the ISO 513 workpiece material group: P (steel), M (stainless), K (cast iron), N (non-ferrous), S (superalloys/titanium), H (hard materials).
- Number — Application range: 10 = finishing, 20 = medium/semi-roughing, 30 = roughing.
For example, WAK20 denotes a Walter CVD-coated grade for ISO P (steel) turning in the medium application range. Similarly, WMM10 indicates a Walter PVD-coated grade for ISO M (stainless steel) finishing operations.
Walter’s proprietary Tiger·tec coating platform enhances this system with optimized multilayer architectures. Tiger·tec Silver CVD coatings feature a silver-colored top layer that reduces friction and improves chip flow, while Tiger·tec Gold PVD coatings use TiAlN-based architectures with gold-colored TiN top layers for wear identification.
ISO P — Steel Turning Grades
Steel (ISO P) represents the largest segment of turning applications. Walter offers both CVD (WAK series) and PVD (WPP series) coated carbide grades for steel turning, covering applications from precision finishing to heavy roughing.
WAK Series — CVD Coated for Steel
The WAK series utilizes Walter’s Tiger·tec Silver CVD coating, featuring a TiCN-Al₂O₃ multilayer with a silver top layer. This architecture provides excellent wear resistance and thermal stability for continuous and light-interrupted cuts.
| Grade | Coating | Application | Vc (m/min) | f (mm/rev) | ap (mm) |
|---|---|---|---|---|---|
| WAK10 | CVD TiCN-Al₂O₃ | Finishing | 200–280 | 0.10–0.30 | 0.5–2.0 |
| WAK20 | CVD TiCN-Al₂O₃ | Medium | 180–250 | 0.20–0.50 | 1.0–4.0 |
| WAK30 | CVD TiCN-Al₂O₃ | Roughing | 150–220 | 0.30–0.80 | 2.0–8.0 |
WPP Series — PVD Coated for Steel
The WPP series features Walter’s Tiger·tec Gold PVD coating (TiAlN-TiN multilayer), offering superior edge toughness and reduced built-up edge formation. PVD grades excel in operations requiring sharp cutting edges, such as low-depth finishing and interrupted cuts.
| Grade | Coating | Application | Vc (m/min) | f (mm/rev) | ap (mm) |
|---|---|---|---|---|---|
| WPP10 | PVD TiAlN-TiN | Finishing | 150–250 | 0.05–0.25 | 0.3–2.0 |
| WPP20 | PVD TiAlN-TiN | Medium | 120–220 | 0.10–0.40 | 0.5–3.0 |
| WPP30 | PVD TiAlN-TiN | Roughing | 100–180 | 0.20–0.60 | 1.0–6.0 |
Selection guidance: Choose WAK (CVD) grades for continuous cuts and higher cutting speeds on stable workpieces. Select WPP (PVD) grades when sharper edges are needed, for low-rigidity setups, or when cutting alloy steels with tendency toward built-up edge.
ISO M — Stainless Steel Turning Grades
Stainless steels (ISO M) present challenges including work hardening, low thermal conductivity, and high ductility. Walter’s stainless turning grades use both CVD (WAM series) and PVD (WMM series) coatings, with PVD grades preferred for most stainless applications due to their sharper edges and reduced work hardening.
| Grade | Coating | Application | Vc (m/min) | f (mm/rev) | ap (mm) |
|---|---|---|---|---|---|
| WAM10 | CVD TiCN-Al₂O₃ | Finishing | 120–180 | 0.10–0.25 | 0.5–2.0 |
| WAM20 | CVD TiCN-Al₂O₃ | Medium | 100–160 | 0.15–0.40 | 1.0–3.5 |
| WMM10 | PVD TiAlN-TiN | Finishing | 100–200 | 0.05–0.20 | 0.3–1.5 |
| WMM20 | PVD TiAlN-TiN | Medium | 90–170 | 0.10–0.35 | 0.5–3.0 |
Key recommendation: For austenitic stainless steels (AISI 304, 316), PVD-coated WMM grades are strongly preferred. The sharper PVD edge reduces work hardening and produces better surface finishes. Maintain feed rates above 0.05 mm/rev to avoid rubbing and work hardening of the cut surface.
ISO K — Cast Iron Turning Grades
Cast iron (ISO K) encompasses gray cast iron (GG/GJL), ductile cast iron (GGG/GJS), and malleable iron. These materials produce abrasive chip particles that cause rapid flank wear. Walter’s WKK series uses CVD coatings optimized for cast iron’s abrasive wear mechanisms.
| Grade | Coating | Application | Vc (m/min) | f (mm/rev) | ap (mm) |
|---|---|---|---|---|---|
| WKK10 | CVD TiCN-Al₂O₃ | Finishing | 150–250 | 0.10–0.30 | 0.5–2.0 |
| WKK20 | CVD TiCN-Al₂O₃ | Medium | 120–220 | 0.20–0.50 | 1.0–4.0 |
For gray cast iron (GJL250, GJL300), higher cutting speeds (200–250 m/min) are achievable due to the material’s favorable chip formation. Ductile cast iron (GJS400, GJS500) requires slightly lower speeds (150–200 m/min) and higher feed rates to manage the longer, more ductile chips.
ISO N — Non-Ferrous Metals Turning Grades
Non-ferrous metals (ISO N) include aluminum alloys, copper, brass, and plastics. These materials have low hardness but tend to adhere to cutting edges, causing built-up edge. Walter offers uncoated (WNN series) and PVD-coated (WSN series) grades for non-ferrous applications.
| Grade | Coating | Application | Vc (m/min) | f (mm/rev) | ap (mm) |
|---|---|---|---|---|---|
| WNN10 | Uncoated polished | Finishing | 300–600 | 0.05–0.20 | 0.3–2.0 |
| WSN10 | PVD diamond-like | Finishing/Medium | 200–500 | 0.05–0.25 | 0.3–3.0 |
For high-silicon aluminum alloys (Si > 12%), polycrystalline diamond (PCD) inserts are recommended over carbide grades due to silicon particles’ extreme abrasiveness. WNN10 with a highly polished rake face minimizes adhesion and produces mirror-like surface finishes on wrought aluminum alloys.
ISO S — Superalloy and Titanium Turning Grades
Superalloys and titanium alloys (ISO S) represent the most challenging turning materials due to high temperature strength, low thermal conductivity, and strain hardening. Walter’s WSS and WSM PVD-coated grades feature heat-resistant coating architectures designed for these demanding applications.
| Grade | Coating | Application | Vc (m/min) | f (mm/rev) | ap (mm) |
|---|---|---|---|---|---|
| WSS10 | PVD TiAlN | Finishing | 30–60 | 0.05–0.15 | 0.3–1.5 |
| WSM10 | PVD TiAlN | Medium | 25–50 | 0.10–0.25 | 0.5–2.5 |
Critical parameters for ISO S:
- Maintain low cutting speeds (25–60 m/min) to prevent rapid tool wear from high cutting temperatures.
- Keep depth of cut above the work-hardened layer (typically > 0.3 mm) to avoid machining strain-hardened material.
- Use sharp edges with positive geometry to minimize heat generation.
- Apply high-pressure coolant (HPC) at 70 bar or higher when available to improve chip breaking and reduce cutting zone temperature.
For Inconel 718 (nickel-based superalloy), target Vc of 30–45 m/min with WSS10 in finishing and 25–35 m/min with WSM10 in roughing. For Ti-6Al-4V (titanium alloy), maintain Vc at 40–55 m/min with aggressive coolant application.
ISO H — Hard Material Turning Grades
Hard turning (ISO H) involves materials hardened above 45 HRC, including hardened steel, chilled cast iron, and hardfacing alloys. Walter offers CBN (WHH series) and ceramic (WHK series) grades for these applications, enabling turning as an alternative to grinding.
| Grade | Material | Application | Vc (m/min) | f (mm/rev) | ap (mm) |
|---|---|---|---|---|---|
| WHH10 | CBN (cubic boron nitride) | Finishing | 100–200 | 0.05–0.20 | 0.1–0.5 |
| WHK10 | Mixed ceramic (Al₂O₃-TiC) | Finishing | 150–300 | 0.05–0.15 | 0.1–0.3 |
WHH10 (CBN) is recommended for hardened steels (55–65 HRC) requiring high surface finish quality (Ra < 0.4 µm). WHK10 (ceramic) achieves higher cutting speeds but is more sensitive to process interruptions and requires rigid setups. For continuous hard turning of bearing steel (100Cr6, 60–62 HRC), WHH10 at Vc 120–150 m/min, f 0.05–0.10 mm/rev, and ap 0.15–0.30 mm produces surface finishes comparable to grinding.
Cross-Brand Grade Comparison
For shops using multiple tool suppliers, the following table maps Walter turning grades to comparable grades from Sandvik Coromant, Iscar, and Seco:
| Walter | Sandvik | Iscar | Seco | ISO Group / Application |
|---|---|---|---|---|
| WAK20 | GC4225 | IC810 | TP2500 | P — Steel, CVD medium |
| WPP20 | GC1105 | IC20 | CP500 | P — Steel, PVD medium |
| WMM10 | GC1115 | IC5010 | CP200 | M — Stainless, PVD finishing |
| WKK10 | GC3210 | IC418 | TK2001 | K — Cast iron, CVD finishing |
| WNN10 | H10A | IC4 | FN10 | N — Non-ferrous, uncoated |
| WSS10 | GC1105 | IC20 | CP500 | S — Superalloy, PVD finishing |
| WHH10 | CB7015 | IB20H | CBN100 | H — Hard, CBN finishing |
Note that while these grades serve similar application ranges, actual cutting performance may differ due to variations in substrate composition, coating thickness, and post-coating edge preparation. Always validate parameters with a production test when switching brands.
Cross-Category Parameter Summary
The following table provides a quick-reference overview of recommended starting parameters across all ISO material groups:
| ISO Group | Material Example | Grade | Vc (m/min) | f (mm/rev) | ap (mm) |
|---|---|---|---|---|---|
| P | AISI 1045 (C45) | WAK20 | 200 | 0.30 | 2.5 |
| P | AISI 4140 (42CrMo4) | WPP20 | 170 | 0.25 | 2.0 |
| M | AISI 304 (X5CrNi18-10) | WMM10 | 140 | 0.12 | 1.0 |
| M | AISI 316 (X5CrNiMo17-12-2) | WMM20 | 120 | 0.20 | 1.5 |
| K | GJL250 (Gray CI) | WKK20 | 200 | 0.35 | 2.5 |
| K | GJS500 (Ductile CI) | WKK10 | 170 | 0.20 | 1.5 |
| N | AlSi1MgMn (6082) | WNN10 | 450 | 0.12 | 1.0 |
| S | Inconel 718 | WSS10 | 35 | 0.08 | 0.5 |
| S | Ti-6Al-4V | WSM10 | 45 | 0.12 | 1.0 |
| H | 100Cr6 (60 HRC) | WHH10 | 130 | 0.08 | 0.2 |
Grade Selection Strategy
Selecting the optimal Walter turning grade requires consideration of four key factors:
- Workpiece material — Determines the ISO group (P/M/K/N/S/H) and narrows the grade selection to the corresponding third-letter designation.
- Machining operation — Finishing (10), medium (20), or roughing (30) determines the numeric suffix based on depth of cut and feed requirements.
- Cut condition — Continuous cuts favor CVD (A-series) coatings for higher wear resistance and speed. Interrupted or light cuts favor PVD (P-series) coatings for edge toughness.
- Machine capability — Higher rigidity and power enable CVD grades at higher speeds. Less rigid setups benefit from PVD grades with sharper geometries and lower cutting forces.
When transitioning between ISO groups, always verify cutting parameters against the workpiece’s specific hardness, heat treatment condition, and chip-breaking characteristics. The parameters provided in this reference represent starting values for stable, continuous cutting conditions with adequate coolant supply. Actual machining should begin at 70–80% of the listed Vc and increase incrementally based on tool wear, surface finish, and chip control results.
Walter’s systematic grade naming convention enables machinists to quickly identify the appropriate insert for any application. By encoding coating technology, ISO material group, and application range in each grade designation, the system simplifies tool selection across the full spectrum of turning operations — from soft aluminum finishing at 600 m/min to hard turning at 65 HRC with CBN.
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