30-Second Summary: The table below summarizes recommended deep hole drilling parameters for less common materials. For unfamiliar materials, always start from the lower limit. The most critical safety note: never use water-based coolant on magnesium — it reacts to produce flammable hydrogen gas. For copper and its alloys, use higher feed rates to produce thick, breakable chips rather than stringy tangles.
| Material | Typical Grade | Vc m/min | Feed* mm/rev | Coolant Pressure | Notes |
|---|---|---|---|---|---|
| Copper (pure) | C110, C101 | 60-120 | 0.02-0.10 | 30-50 bar | Gummy, long stringy chips. Use higher feed to produce thick breakable chips. Maintain coolant temp 20-22°C. Filtration <20 μm to prevent buildup on bearing pads. IT8-IT9 achievable. |
| Brass | C360 (free-cutting) | 80-150 | 0.02-0.08 | 20-40 bar | Easy to machine, watch for burrs on exit. Higher lead content improves chip breaking. For dezincification-resistant brasses, reduce Vc by 20%. |
| Bronze | C932 (SAE 660) | 60-100 | 0.02-0.06 | 30-50 bar | Abrasive material (high tin content), faster tool wear. Use K-grade carbide. Aluminum bronzes are more abrasive than tin bronzes. |
| Magnesium alloy | AZ31, AZ91 | 100-200 | 0.05-0.15 | 20-30 bar | ⚠️ No water-based coolant (produces hydrogen gas!). Use dry machining or light mineral oil only. Keep Class D fire extinguisher + dry sand available. Never use water, foam, or CO₂ on a magnesium fire. Sharp tooling essential. |
| Nickel-based alloy | Monel 400 | 20-35 | 0.01-0.03 | ≥80 bar | Severe adhesion, high coolant pressure, polished rake face to reduce material pickup |
| Cobalt-based alloy | Stellite 6B | 15-25 | 0.01-0.02 | ≥100 bar | Extremely wear-resistant, PCBN tooling recommended for production. Carbide feasible for short runs but expect short tool life. |
| Tool steel (annealed) | D2, O1, A2 | 50-70 | 0.02-0.05 | 60-100 bar | High carbide content (especially D2 with ~12% Cr), monitor tool wear at guide pads. AlTiCrN coating recommended. |
| Tool steel (hardened) | D2 (HRC 58-62) | 15-25 | 0.01-0.03 | ≥80 bar | PCBN or CBN-coated tooling. See hardened steel guide for details. |
| Maraging steel | C300, C350 | 30-50 | 0.015-0.04 | ≥80 bar | High toughness, excellent surface finish achievable (Ra <0.4 possible). Maintain continuous feed. |
| Carburized steel (post-carburizing) | 20CrMnTi, 8620 | 20-35 | 0.01-0.03 | ≥80 bar | Hard surface (>HRC 58), tough core. Beware of transition zone — reduce feed by 20% when crossing from case to core. |
| Tungsten carbide (green) | WC-Co (pre-sintered) | 10-20 | 0.005-0.015 | 30-50 bar | Extremely abrasive. Diamond or PCD tooling mandatory. Use high-volume coolant to flush abrasive slurry. Do not use on sintered (finished) carbide. |
| Powder metallurgy | Various | 30-60 | 0.02-0.05 | 30-60 bar | Porosity affects thermal conductivity, avoid excessive coolant pressure that could impregnate pores. Burr formation at exit can be unpredictable. |
| Plastic/Composite | PEEK, CFRP, GFRP | 50-150 | 0.01-0.05 | 10-20 bar (air or mist) | Delamination risk at entry/exit, PCD tooling recommended for production. Use support board at exit. For CFRP, reduce feed at exit to prevent fiber tear-out. |
| Tantalum | Ta, Ta-10W | 15-30 | 0.01-0.03 | ≥80 bar | High density, high melting point. Gummy, requires sharp tooling and continuous feed. High coolant pressure essential to remove chips from deep holes. |
| Zirconium | Zr 702, Zr 705 | 25-45 | 0.01-0.04 | ≥60 bar | Fire risk similar to titanium — fine chips are pyrophoric. No water-based coolant. Use oil-based only. |
* Feed reference values for D=10mm. For smaller diameters, reduce feed proportionally; for larger diameters, increase.
💡 First-article procedure for new materials: 1. Find the closest material group in the table above — 2. Use the lower bound of recommended Vc and feed — 3. Trial-cut 10-20mm then inspect chip shape and surface quality — 4. Optimize parameters incrementally based on chip condition. Monitor the first 5-10 holes closely for tool wear patterns before increasing throughput.
⚠️ Critical material safety: Magnesium and zirconium produce pyrophoric chips that can ignite spontaneously. Never use water-based coolants on these materials — hydrogen gas generation creates an explosion risk. Use dry machining or oil-based coolant only. Keep Class D fire extinguishers accessible and store chips in sealed metal containers.