Start with the Material, Not the Tool
Stainless steels work-harden within 0.1 s; every subsequent cut must penetrate the previous hardened layer.
Goal: stay below the work-hardening threshold by shearing, not rubbing.
Insert Grade & Coating
Substrate: tough, sub-micron grain carbide (6–10 % Co) to resist thermal cycling.
Coating: multi-layer PVD AlTiN + TiSiN (3–4 µm) for 900 °C barrier; add Si for nano-layer toughness.
For 17-4 PH ≥ 38 HRC: switch to CBN or ceramic (Sialon) at lower speeds.
Macro-Geometry
Positive rake 8–12° to reduce cutting forces 15–25 %.
Sharp hone ≤ 0.02 mm; larger hone increases rubbing and white-layer depth.
Chip-breaker groove matched to feed (f = 0.08–0.20 mm/rev) for short, curled chips.
Toolholder & Setup
Hydraulic or shrink-fit for < 3 µm run-out; every 10 µm run-out cuts tool life in half.
Shortest gauge length ≤ 4 × D to push chatter above 8 kHz-outside the machine's modal range.
Recommended Cutting Data (flood or 7 MPa HP coolant)
表格
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| Grade | Operation | Vc (m/min) | f (mm/rev) | ap (mm) | Tool Life Target |
|---|---|---|---|---|---|
| 303 | Rough | 120–150 | 0.15–0.25 | 1–2 | 20 min |
| 303 | Finish | 150–180 | 0.05–0.10 | 0.1–0.3 | 30 min |
| 304/316L | Rough | 80–120 | 0.12–0.20 | 1–2 | 15 min |
| 304/316L | Finish | 120–150 | 0.05–0.08 | 0.05–0.2 | 25 min |
| 17-4 PH | Rough | 60–80 | 0.10–0.15 | 0.5–1.5 | 10 min |
| 17-4 PH | Finish | 100–120* | 0.03–0.06 | 0.02–0.1 | 15 min |
| *CBN or ceramic at 150–200 m/min for continuous cut. |
Feed-to-Edge Rule
Feed must be ≥ hone radius; otherwise the tool rubs: f ≥ rε × 0.5.
For a 0.04 mm hone, minimum feed 0.02 mm/rev-use this as the absolute lower limit.
Depth-of-Cut Strategy
Rough: ap ≥ 0.2 mm to penetrate the hardened skin left by the previous cut.
Semi-finish: 0.1 mm; finish: 0.02–0.05 mm to keep cutting force < 200 N and avoid part deflection on thin walls.
Coolant Delivery
Target 7 MPa, 30 l/min through-tool; reduces edge temperature 150 °C and extends life 30 %.
Chloride content < 60 ppm to prevent pitting during long runs; pH 8.5–9.2.
Tool-Life Monitoring
Use spindle power curve: ± 5 % rise signals edge degradation; change insert before surface finish jumps > 0.2 µm Ra.
In-cell air-gauge or laser: dimensional drift > 6 µm is another reliable wear flag.
Cost-per-Edge Calculation
Example: coated carbide insert (double-sided, 4 edges) costs USD 6.50; expected 20 min life at Vc 100 m/min on 304.
One edge machines 1.25 m part length → cost = USD 6.50 / 4 / 1.25 = USD 1.30 per metre, competitive with re-grind.
