Chip adhesion and work hardening are the two biggest challenges. SS-specific geometry and high-pressure coolant are essential. Austenitic grades (304/316) are the most difficult. Never use TiN-only coatings — they lack heat resistance. Maintain feed at all costs.
| Type | Grades | Challenge | Countermeasure |
|---|---|---|---|
| Ferritic | 430 | Moderate | Standard tooling, moderate Vc |
| Martensitic | 410, 420 | Hardness variation (can exceed 400 HB) | Account for pre/post tempering differences |
| Austenitic | 304, 316, 321 | Chip adhesion, work hardening | SS geometry, AlTiN coating, ≥80 bar coolant, forced feed |
| Duplex | 2205, 2507 | High hardness + adhesion | AlTiCrN coating, ≥100 bar, lower Vc |
| Precipitation-hardening | 17-4PH, 15-5PH | Hardness varies with heat treat | Match parameters to specific condition (H900: ~400 HB vs H1150: ~280 HB) |
| Grade | Type | Machinability | Vc (m/min) |
|---|---|---|---|
| 303 | Austenitic (free-machining) | Best | 50–70 |
| 304 | Austenitic (standard) | Moderate | 35–55 |
| 316 | Austenitic (corrosion-resistant) | Moderate–Poor | 30–50 |
| 416 | Martensitic (free-machining) | Good | 50–70 |
| 17-4PH | Precipitation-hardening | Moderate | 25–45 |
| Grade | Condition | Result | Source |
|---|---|---|---|
| SUS 304 | Graphene nanofluid at 1.5 bar, 5mm drill, Ø5mm × 40mm, single-stroke | All speed/feed combos succeeded. Conventional emulsion failed at higher feeds (tool breakage). Nanofluid reduced thrust force and extended tool life. | ETASR, Dec 2025 |
| AISI 304 | Deep hole L/D=15, HPC pressure sweep 20–80 bar | Optimal chip breaking at 50 bar. Ra 1.6μm at 50 bar vs Ra >3.2μm at 80 bar (over-fragmentation). | Vellfire Tools, 2026 |
| AISI 304 | HSS screw drill, optimized geometry | Ra <1μm at Vc 32 m/min, f 0.2 mm/rev with 138° point angle, 7° clearance | Scientific Reports, 2023 |
| 304/316 general | Industry best practice | Vc 25–55 (304) / 20–50 (316). Minimum 0.03 mm/rev feed. 135° split point. | Hymson 2026 calculator |
Verify ≥80 bar reaches the tool tip — austenitic stainless needs aggressive chip evacuation.
135–140° split point, AlTiN/AlCr PVD coating, through-coolant.
Enter at low speed but never below 0.03 mm/rev — the tool must cut, not rub.
For L/D >3, full-retract pecks every 0.5–1×D; partial retracts trap chips.
Silver = good. Dark blue/black = excessive heat — reduce Vc or raise coolant pressure. Powder = rubbing.
Never dwell mid-hole — if feed must stop, retract completely first.