30-Second Summary: This table contains data NOT found in the Feeds & Speeds guide — machinability ratings, L/D limits, and recommended carbide grades and coatings. Use it alongside the Feeds & Speeds Tables for complete parameter selection. Materials are organized by ISO classification groups.
ISO P — Steel (Carbon, Alloy, Tool, Stainless Martensitic)
| Material | Machinability* | Max L/D (Gundrill) | Max L/D (BTA) | Carbide Grade | Coating | Coolant |
|---|
| Low-carbon steel (<0.25%C) | 70% | 300:1 | 200:1 | K10–K20 (micrograin) | TiN or uncoated | Oil / Emulsion |
| Medium-carbon steel (≥0.25%C) | 60% | 250:1 | 180:1 | K20–K30 | TiN / TiAlN | Oil / Emulsion |
| Alloy steel, annealed (4140, 4340) | 55% | 200:1 | 150:1 | K20–K30 | TiAlN | Oil (preferred) / Emulsion |
| Alloy steel, Q&T (HRC 30–45) | 35% | 100:1 | 80:1 | K30–K40 | AlTiN | Oil only |
| Tool steel (H-13, D-2, annealed) | 45% | 100:1 | 80:1 | K20–K30 | TiAlN / AlTiN | Oil |
| Hardened steel HRC 45–55 | 20% | 50:1 | 40:1 | K40 / PCBN | AlTiN / TiSiN | Oil (high EP) |
| Hardened steel HRC 55–62 | 12% | 30:1 | 25:1 | PCBN | Uncoated (PCBN) | Oil (high EP) |
ISO M — Stainless Steel (Austenitic, Duplex, Ferritic)
| Material | Machinability* | Max L/D (Gundrill) | Max L/D (BTA) | Carbide Grade | Coating | Coolant |
|---|
| Austenitic stainless (304, 316, 321) | 40% | 100:1 | 80:1 | K20–K30 (fine grain) | TiAlN (best) | Oil (high EP) — 8–10% concentration if emulsion |
| Ferritic stainless (430, 409) | 50% | 120:1 | 90:1 | K20–K30 | TiAlN | Oil / Emulsion |
| Martensitic stainless (410, 420, annealed) | 45% | 100:1 | 80:1 | K20–K30 | TiAlN / AlTiN | Oil |
| Duplex / Super Duplex stainless | 30% | 80:1 | 60:1 | K30–K40 | TiAlN / TiSiN | Oil (high EP) |
| Precipitation-hardening (17-4PH) | 35% | 80:1 | 60:1 | K20–K30 | TiAlN | Oil |
ISO K — Cast Iron
| Material | Machinability* | Max L/D (Gundrill) | Max L/D (BTA) | Carbide Grade | Coating | Coolant |
|---|
| Gray cast iron (GG20, GG25) | 110% | 200:1 | 150:1 | K10–K20 | Uncoated / TiAlN | Emulsion / Dry** |
| Ductile cast iron (GGG40, GGG70) | 90% | 180:1 | 130:1 | K10–K20 | Uncoated / TiAlN | Emulsion |
| Compact graphite iron (CGI) | 60% | 100:1 | 80:1 | K20–K30 | TiAlN / AlCrN | Emulsion (7% concentration) |
ISO N — Non-Ferrous (Aluminum, Copper, Magnesium)
| Material | Machinability* | Max L/D (Gundrill) | Max L/D (BTA) | Carbide Grade | Coating | Coolant |
|---|
| Aluminum alloy (wrought, 6061, 7075) | 150% | 200:1 | 150:1 | Uncoated K10 / Diamond | Uncoated (prevents BUE) | Synthetic / Emulsion |
| Aluminum alloy (cast, high Si >12%) | 100% | 150:1 | 120:1 | PCD / Diamond-coated | Uncoated / Diamond | Synthetic / Kerosene |
| Brass / Bronze (leaded) | 100% | 250:1 | 150:1 | Uncoated K10–K20 | Uncoated | Synthetic / Emulsion |
| Copper (pure, OFHC) | 70% | 150:1 | 100:1 | Uncoated K10–K20 | Uncoated (polished) | Emulsion / Oil |
| Magnesium alloy | 200% | 150:1 | 100:1 | Uncoated K10–K20 | Uncoated | Mineral oil only (NO water) |
ISO S — Superalloys and Titanium
| Material | Machinability* | Max L/D (Gundrill) | Max L/D (BTA) | Carbide Grade | Coating | Coolant |
|---|
| Titanium alloy (Ti-6Al-4V) | 25% | 80:1 | 60:1 | K10–K20 (fine grain) | TiAlN or TiSiN (best) | Oil (high EP) — 10–12% if emulsion |
| Titanium (pure, Grade 2) | 35% | 100:1 | 80:1 | K10–K20 | Uncoated / TiAlN | Oil |
| Inconel 718 | 12% | 50:1 | 40:1 | S10–S20 / fine-grain K | TiSiN or TiAlN (best) | Oil (high EP, S-based additives) |
| Inconel 625 / Hastelloy | 10% | 40:1 | 30:1 | S10–S20 | TiSiN / TiAlSiN | Oil (high EP) |
| Waspaloy / René 41 | 8% | 30:1 | 25:1 | S20–S30 | TiSiN | Oil (high EP) |
ISO H — Hardened Steel
| Material | Machinability* | Max L/D (Gundrill) | Max L/D (BTA) | Carbide Grade | Coating | Coolant |
|---|
| Hardened steel HRC 45–55 | 20% | 50:1 | 40:1 | K40 / PCBN | AlTiN / TiSiN | Oil (high EP) |
| Hardened steel HRC 55–62 | 12% | 30:1 | 25:1 | PCBN | Uncoated (PCBN) | Oil (high EP) |
| Chilled cast iron (Ni-hard) | 15% | 30:1 | 25:1 | PCBN / Ceramic | Uncoated | Emulsion |
* Machinability percentage relative to AISI 1112 free-machining steel (100%). Higher % = easier to machine.
** Dry roughing possible for cast iron, but guide pads still require lubrication for deep holes. Reduce L/D by 30% for dry machining.
ISO Material Classification Guide
| ISO Group | Color Code | Common Materials | Key Machining Challenge |
|---|
| P | Blue | Steel, alloy steel, tool steel | Built-up edge at low speed; notch wear at high speed |
| M | Yellow | Stainless steel (austenitic, duplex) | Work hardening; long chips; built-up edge |
| K | Red | Cast iron (gray, ductile, CGI) | Abrasive wear; fine graphite dust |
| N | Green | Aluminum, copper, magnesium, plastics | Built-up edge; excellent chip flow — high feeds possible |
| S | Brown | Titanium, nickel superalloys, cobalt alloys | High cutting temperature; work hardening; notching |
| H | Grey | Hardened steel, chilled cast iron | High edge pressure; chipping risk; low L/D only |
Coating Selection Quick Guide
Based on comparative drilling performance studies, coatings ranked by effectiveness:
- TiSiN / TiAlSiN (nanolaminate): Best overall — lowest flank wear, best chip evacuation, highest temperature resistance (1100°C). Use for superalloys, titanium, hardened steel.
- TiAlN: Best general-purpose for deep hole drilling — excellent performance across steel, stainless, and titanium. Consistent results in production.
- AlTiN: Higher aluminum content for better oxidation resistance at high speed. Good for hardened steel and dry machining.
- TiN: Adequate for low-carbon steel only. Limited temperature resistance (600°C).
- Uncoated: Best for aluminum, copper, brass — prevents built-up edge formation.
- Avoid AlTiCrN / Cr-containing coatings for drilling — studies show chromium oxides have lower protective capability, leading to higher adhesion, abrasive wear, edge breakage, and poor chip evacuation compared to TiAlN-based coatings.
💡 How to use this table: Start with the Feeds & Speeds Tables guide for Vc and feed values, then come here to select the right carbide grade, coating, and coolant type. Finally verify your L/D target is within the achievable range for your chosen method and material. For new materials, reduce L/D by 20% for the first trial.
⚠️ Core principle: For any new material, consult the tool manufacturer's recommended parameters first, start from the lower limit, and inspect chip shape every 10 seconds during the first hole. Only increase parameters after confirming stable chip formation and acceptable tool wear rate. Machinability ratings are relative — actual performance depends on machine rigidity, coolant system, and fixturing.