Turning Parameter Calculator: Speed, Feed, and Depth of Cut for Every ISO Group
Dialing in the right turning parameters is the difference between profitable machining and constant tool changes. This reference provides starting-point cutting parameters for turning operations across all major ISO material groups, complete with the formulas you need to convert cutting speed (Vc) into spindle RPM and calculate metal removal rates.
Essential Turning Formulas
| Parameter | Formula | Units |
|---|---|---|
| Spindle Speed (n) | n = (Vc × 1000) / (π × D) | rev/min (RPM) |
| Feed Rate (Vf) | Vf = f × n | mm/min |
| Metal Removal Rate (Q) | Q = Vc × f × ap | cm³/min |
| Cutting Time (Tc) | Tc = L / (f × n) | minutes |
| Spindle Power (Pc) | Pc = (Kc × Q) / 60 | kW |
Where: Vc = cutting speed (m/min), D = workpiece diameter (mm), f = feed per revolution (mm/rev), ap = depth of cut (mm), L = cutting length (mm), Kc = specific cutting force (N/mm²).
ISO P — Steel Turning Parameters
| Sub-Group | Material Description | Hardness (HB) | Roughing Vc | Roughing f (mm/rev) | Roughing ap (mm) | Finishing Vc | Finishing f (mm/rev) | Finishing ap (mm) | Korloy Grade |
|---|---|---|---|---|---|---|---|---|---|
| P10 | Low carbon steel, free-cutting | 125–175 | 300–380 | 0.25–0.45 | 2.0–4.0 | 400–500 | 0.08–0.20 | 0.3–1.0 | PC5300 |
| P20 | Medium carbon steel (C45, 1045) | 175–225 | 250–320 | 0.20–0.40 | 2.0–4.0 | 350–420 | 0.10–0.20 | 0.3–1.0 | PC5300 |
| P30 | Alloy steel (42CrMo4, 4140) | 225–275 | 200–270 | 0.18–0.35 | 1.5–3.5 | 280–360 | 0.10–0.18 | 0.3–0.8 | PC5335 |
| P40 | High alloy steel, hardened 38–48 HRC | 275–350 | 140–200 | 0.12–0.28 | 1.0–2.5 | 200–280 | 0.08–0.15 | 0.2–0.6 | PC5400 |
| P50 | Very hard steel >48 HRC | >350 | 80–140 | 0.08–0.18 | 0.5–1.5 | 120–180 | 0.05–0.10 | 0.1–0.4 | PC3545 / NC3225 |
ISO M — Stainless Steel Turning Parameters
| Sub-Group | Material Description | Roughing Vc | Roughing f (mm/rev) | Roughing ap (mm) | Finishing Vc | Finishing f (mm/rev) | Finishing ap (mm) | Korloy Grade |
|---|---|---|---|---|---|---|---|---|
| M10 | Ferritic SS (430, 409) | 220–300 | 0.20–0.40 | 2.0–3.5 | 300–400 | 0.10–0.18 | 0.2–0.8 | PC5300 / PC215K |
| M20 | Austenitic SS (304, 316L) annealed | 160–220 | 0.18–0.35 | 1.5–3.0 | 220–300 | 0.08–0.18 | 0.2–0.8 | PC215K |
| M30 | Austenitic SS, work-hardened / interrupted | 120–180 | 0.15–0.28 | 1.5–2.5 | 180–250 | 0.08–0.15 | 0.2–0.6 | PC2507 |
| M40 | Duplex SS (2205, 2507) | 100–150 | 0.12–0.25 | 1.0–2.5 | 150–210 | 0.06–0.12 | 0.2–0.6 | PC2507 |
Critical note on stainless: Always maintain a positive feed — never dwell. Austenitic stainless steel work-hardens rapidly, and a zero-feed dwell will create a hardened zone that destroys the insert edge. High-pressure coolant (70+ bar) is strongly recommended.
ISO K — Cast Iron Turning Parameters
| Sub-Group | Material Description | Roughing Vc | Roughing f (mm/rev) | Roughing ap (mm) | Finishing Vc | Finishing f (mm/rev) | Finishing ap (mm) | Korloy Grade |
|---|---|---|---|---|---|---|---|---|
| K10 | Gray iron GJL-200, soft | 280–380 | 0.25–0.50 | 2.5–5.0 | 400–520 | 0.10–0.22 | 0.3–1.2 | KC5305 |
| K20 | Gray iron GJL-300, hard skin | 200–280 | 0.20–0.40 | 2.0–4.0 | 300–400 | 0.10–0.20 | 0.3–1.0 | KC5335 |
| K30 | Nodular iron GJS-500, GJS-600 | 180–260 | 0.18–0.35 | 1.5–3.5 | 260–350 | 0.08–0.18 | 0.2–0.8 | KC5335 |
| K40 | Nodular iron GJS-700+, CGI | 140–200 | 0.15–0.30 | 1.0–3.0 | 200–280 | 0.08–0.15 | 0.2–0.7 | KC5405 |
ISO N — Aluminum & Non-Ferrous Turning Parameters
| Sub-Group | Material Description | Roughing Vc | Roughing f (mm/rev) | Roughing ap (mm) | Finishing Vc | Finishing f (mm/rev) | Finishing ap (mm) | Korloy Grade |
|---|---|---|---|---|---|---|---|---|
| N10 | Wrought Al alloys (6061, 7075) | 400–600 | 0.15–0.35 | 2.0–4.0 | 600–1000 | 0.05–0.15 | 0.2–0.6 | NCM325 / Uncoated |
| N20 | Cast Al alloys (A380, A356) | 300–450 | 0.15–0.30 | 1.5–3.5 | 450–700 | 0.08–0.15 | 0.2–0.8 | NCM325 |
| N30 | Copper alloys (brass, bronze) | 250–400 | 0.15–0.35 | 1.5–3.0 | 400–600 | 0.08–0.18 | 0.2–0.6 | NCM325 / Uncoated |
ISO S — Heat-Resistant Super Alloys (HRSA)
| Sub-Group | Material Description | Roughing Vc | Roughing f (mm/rev) | Roughing ap (mm) | Finishing Vc | Finishing f (mm/rev) | Finishing ap (mm) | Korloy Grade |
|---|---|---|---|---|---|---|---|---|
| S10 | Titanium alloys (Ti-6Al-4V) | 50–80 | 0.10–0.20 | 1.0–2.5 | 80–120 | 0.06–0.12 | 0.2–0.5 | PC3545 |
| S20 | Nickel-based alloys (Inconel 718) | 30–60 | 0.08–0.18 | 0.8–2.0 | 60–90 | 0.05–0.10 | 0.1–0.5 | PC3545 |
| S30 | Cobalt-based alloys (Stellite, Haynes) | 20–45 | 0.06–0.15 | 0.5–1.5 | 45–70 | 0.04–0.08 | 0.1–0.4 | PC3545 |
Key rule for super alloys: Keep ap deeper than the work-hardened layer from the previous pass (typically ≥ 0.5 mm). Use abundant coolant or high-pressure coolant to manage extreme heat generation.
ISO H — Hard Turning Parameters
| Sub-Group | Material Description | Hardness | Vc (m/min) | f (mm/rev) | ap (mm) | Korloy Grade |
|---|---|---|---|---|---|---|
| H10 | Hardened steel 45–55 HRC | 440–580 HB | 120–200 | 0.08–0.18 | 0.2–1.0 | NC3225 |
| H20 | Hardened steel 55–63 HRC | 580–750 HB | 80–150 | 0.05–0.12 | 0.1–0.5 | NC3225 / CBN |
| H30 | Chilled cast iron, hard ceramics | >750 HB | 60–120 | 0.04–0.10 | 0.1–0.4 | CBN inserts |
Worked Example: Turning a 42CrMo4 Shaft
Scenario: Rough turning a 42CrMo4 (AISI 4140) shaft, Ø80 mm, using Korloy PC5335 inserts.
From the P30 row: Vc = 250 m/min, f = 0.30 mm/rev, ap = 2.5 mm
- Spindle speed: n = (250 × 1000) / (3.1416 × 80) = 995 RPM
- Feed rate: Vf = 0.30 × 995 = 298 mm/min
- Metal removal rate: Q = 250 × 0.30 × 2.5 = 187.5 cm³/min
- Cutting time for 200 mm length: Tc = 200 / (0.30 × 995) = 0.67 minutes
Adjustment Factors
| Condition | Vc Adjustment | f Adjustment | ap Adjustment |
|---|---|---|---|
| Interrupted cut | −20% to −30% | −10% | −20% |
| Long overhang (>4×D) | −15% | −20% | −30% |
| High-pressure coolant (70+ bar) | +10% to +15% | No change | No change |
| Forging/casting scale on first pass | −15% to −25% | No change | Increase past scale layer |
| Ceramic insert (Si₃N₄, Al₂O₃) | +80% to +150% | −30% | −50% |
Need help optimizing your turning parameters? The machining experts at hooguu.com offer free cutting parameter consultations. We stock the full Korloy turning insert range and can recommend the ideal grade, chipbreaker, and geometry for your application.
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